0001564590-21-009415 | 10-K | XBRL Viewer

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Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	SWAV
Entity Registrant Name	Shockwave Medical, Inc.
Entity Central Index Key	0001642545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		34,842,744
Entity Public Float			$ 1.3
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-38829
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0494101
Entity Address, Address Line One	5403 Betsy Ross Drive
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	510
Local Phone Number	279-4262
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Shockwave Medical Inc., common stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	Portions of the registrant’s Proxy Statement for its 2021 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2020.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 50,423	$ 139,045
Short-term investments	151,931	56,304
Accounts receivable, net	11,689	7,377
Inventory	29,859	12,074
Prepaid expenses and other current assets	2,398	1,897
Total current assets	246,300	216,697
Operating lease right-of-use assets	7,568	8,825
Property and equipment, net	16,362	4,910
Other assets	1,812	1,506
TOTAL ASSETS	272,042	231,938
CURRENT LIABILITIES:
Accounts payable	1,466	2,790
Term notes, current portion	3,300	6,667
Accrued liabilities	19,942	13,777
Lease liability, current portion	873	774
Total current liabilities	25,581	24,008
Lease liability, noncurrent portion	7,488	8,125
Term notes, noncurrent portion	13,319	7,152
TOTAL LIABILITIES	46,388	39,285
Commitments and contingencies (Note 6)
STOCKHOLDERS’ EQUITY:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized; No shares issued and outstanding as of December 31, 2020 and 2019
Common stock, $0.001 par value; 281,274,838 shares authorized; 34,684,337 and 31,446,787 issued and outstanding as of December 31, 2020 and 2019	35	31
Additional paid-in capital	469,283	370,561
Accumulated other comprehensive income	9	35
Accumulated deficit	(243,673)	(177,974)
TOTAL STOCKHOLDERS’ EQUITY	225,654	192,653
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 272,042	$ 231,938

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	281,274,838	281,274,838
Common stock, shares issued	34,684,337	31,446,787
Common stock, shares outstanding	34,684,337	31,446,787

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Product revenue	$ 67,789,000	$ 42,927,000	$ 12,263,000
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost of revenue:
Cost of product revenue	$ 20,991,000	$ 17,159,000	$ 7,250,000
Type of Cost, Good Or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 46,798,000	$ 25,768,000	$ 5,013,000
Operating expenses:
Research and development	36,926,000	32,853,000	22,698,000
Sales and marketing	51,672,000	30,620,000	17,536,000
General and administrative	23,863,000	14,134,000	5,979,000
Total operating expenses	112,461,000	77,607,000	46,213,000
Loss from operations	(65,663,000)	(51,839,000)	(41,200,000)
Interest expense	(1,212,000)	(944,000)	(401,000)
Change in fair value of warrant liability		(609,000)	(52,000)
Other income, net	1,256,000	2,345,000	589,000
Net loss before taxes	(65,619,000)	(51,047,000)	(41,064,000)
Income tax provision	80,000	62,000	38,000
Net loss	(65,699,000)	(51,109,000)	(41,102,000)
Unrealized gain (loss) on available-for-sale securities	(5,000)	35,000	1,000
Adjustment for net gain realized and included in other income, net	(21,000)
Total comprehensive loss	$ (65,725,000)	$ (51,074,000)	$ (41,101,000)
Net loss per share, basic and diluted	$ (1.99)	$ (2.14)	$ (23.39)
Shares used in computing net loss per share, basic and diluted	33,088,095	23,904,828	1,757,102

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Total	Initial Public Offering	Public Offering	Convertible Preferred Stock	Common Stock	Common Stock Initial Public Offering	Common Stock Public Offering	Additional Paid-In Capital	Additional Paid-In Capital Initial Public Offering	Additional Paid-In Capital Public Offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ (83,292,000)				$ 2,000			$ 2,470,000			$ (1,000)	$ (85,763,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2017				17,510,045
Temporary equity, Beginning balance at Dec. 31, 2017				$ 137,469,000
Beginning balance, Shares at Dec. 31, 2017					1,627,032
Issuance of common stock warrants	104,000							104,000
Issuance of convertible preferred stock, net of issuance costs				$ 14,920,000
Issuance of convertible preferred stock, net of issuance costs, Shares				1,090,608
Exercise of Series A-1 warrants				$ 417,000
Temporary equity, Exercise of Series A-1 warrants, Shares				69,675
Exercise of stock options	$ 326,000							326,000
Exercise of stock options, Shares	197,820				197,820
Unrealized gain (loss) on available-for-sale securities	$ 1,000										1,000
Vesting of early exercised options	78,000							78,000
Stock-based compensation	1,297,000							1,297,000
Net loss	(41,102,000)											(41,102,000)
Ending balance at Dec. 31, 2018	(122,588,000)				$ 2,000			4,275,000				(126,865,000)
Temporary equity, Ending balance, Shares at Dec. 31, 2018				18,670,328
Temporary equity, Ending balance at Dec. 31, 2018				$ 152,806,000
Ending balance, Shares at Dec. 31, 2018					1,824,852
Exercise of common stock warrants for cash	110,000							110,000
Exercise of common stock warrants for cash, Shares					50,331
Issuance of common stock upon net exercise of warrants	133,000							133,000
Issuance of common stock upon net exercise of warrants, Shares					180,952
Conversion of preferred stock to common stock upon initial public offering	152,806,000				$ 18,000			152,788,000
Temporary equity, Conversion of preferred stock to common stock upon initial public offering, Shares				(18,670,328)
Temporary equity, Conversion of preferred stock to common stock upon initial public offering				$ (152,806,000)
Conversion of preferred stock to common stock upon initial public offering, Shares					18,670,328
Conversion of Series A-1 warrants to common stock warrants upon initial public offering	789,000							789,000
Issuance of common stock		$ 99,924,000	$ 96,677,000			$ 7,000	$ 3,000		$ 99,917,000	$ 96,674,000
Issuance of common stock, Shares						6,555,000	2,854,048
Issuance of common stock in connection with private placement	10,000,000				$ 1,000			9,999,000
Issuance of common stock in connection with private placement, Shares					588,235
Exercise of stock options	$ 2,206,000							2,206,000
Exercise of stock options, Shares	722,242				723,155
Unrealized gain (loss) on available-for-sale securities	$ 35,000										35,000
Vesting of early exercised options	27,000							27,000
Stock-based compensation	3,646,000							3,646,000
Adjustment for fractional shares resulting from reverse stock split	(3,000)							(3,000)
Adjustment for fractional shares resulting from reverse stock split, Shares					(114)
Net loss	(51,109,000)											(51,109,000)
Ending balance at Dec. 31, 2019	192,653,000				$ 31,000			370,561,000			35,000	(177,974,000)
Ending balance, Shares at Dec. 31, 2019					31,446,787
Issuance of common stock			$ 83,368,000				$ 2,000			$ 83,366,000
Issuance of common stock, Shares							1,955,000
Exercise of stock options	$ 4,317,000				$ 2,000			4,315,000
Exercise of stock options, Shares	1,185,764				1,185,764
Issuance of common stock under employee stock purchase plan	$ 1,795,000							1,795,000
Issuance of common stock under employee stock purchase plan, Share					52,612
Issuance of common stock in connection with vesting of restricted stock units, Shares					69,900
Unrealized gain (loss) on available-for-sale securities	(5,000)										(5,000)
Restricted stock units withheld in net settlement for tax	(1,420,000)							(1,420,000)
Restricted stock units withheld in net settlement for tax, Shares					(25,726)
Stock-based compensation	10,666,000							10,666,000
Net gain reclassified from accumulated other comprehensive income	(21,000)										(21,000)
Net loss	(65,699,000)											(65,699,000)
Ending balance at Dec. 31, 2020	$ 225,654,000				$ 35,000			$ 469,283,000			$ 9,000	$ (243,673,000)
Ending balance, Shares at Dec. 31, 2020					34,684,337

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Issuance cost			$ 80
Initial Public Offering
Issuance costs		$ 11,500
Public Offering
Issuance costs	$ 6,100	$ 6,800

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (65,699)	$ (51,109)	$ (41,102)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,863	1,337	700
Stock-based compensation	10,350	3,646	1,297
Amortization of right-of-use assets	1,483	944
Accretion of discount on available-for-sale securities	300	(543)
Loss on write down of fixed assets	187	67	31
Change in fair value of warrant liability		609	52
Amortization of debt issuance costs	646	436	206
Changes in operating assets and liabilities:
Accounts receivable	(4,312)	(4,527)	(2,211)
Inventory	(17,056)	(6,824)	(2,608)
Prepaid expenses and other current assets	(501)	(785)	(144)
Other assets	(306)	41	(917)
Accounts payable	(1,392)	1,272	360
Accrued and other current liabilities	4,017	8,339	2,773
Lease liabilities	(764)	(1,010)
Other liabilities			98
Net cash used in operating activities	(71,184)	(48,107)	(41,465)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(167,953)	(119,476)
Proceeds from maturities of available-for-sale securities	72,000	63,750	1,807
Purchase of property and equipment	(11,520)	(3,817)	(1,981)
Net cash used in investing activities	(107,473)	(59,543)	(174)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock upon initial public offering, net of issuance costs paid		100,547
Proceeds from issuance of convertible preferred stock, net of issuance costs			14,920
Proceeds from issuance of common stock in private placement		10,000
Proceeds from issuance of common stock in public offering, net of issuance costs paid	83,368	96,856
Payments of taxes withheld on net settled vesting of restricted stock units	(1,420)
Proceeds from term loans	3,265		14,988
Payment of deferred offering costs	(179)		(626)
Proceeds from stock option exercises	4,317	2,206	426
Proceeds from issuance of common stock under employee stock purchase plan	1,795
Proceeds from warrant exercises		110	101
Principal payment of term loan	(1,111)	(1,667)
Net cash provided by financing activities	90,035	208,052	29,809
Net increase (decrease) in cash, cash equivalents and restricted cash	(88,622)	100,402	(11,830)
Cash, cash equivalents and restricted cash at beginning of period	140,495	40,093	51,923
Cash, cash equivalents and restricted cash equivalents at end of period	51,873	140,495	40,093
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	549	534	156
Income tax paid	22	120	5
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued on conversion of convertible preferred stock		152,806
Issuance of Series A-1 convertible preferred stock on net exercise of warrants			316
Deferred offering cost included in account payable and accrued liabilities			893
Offering cost included in account payable and accrued liabilities		179
Common stock warrants issued on conversion of preferred stock warrants and the reclassification of the warrant liability		789
Right-of-use asset obtained in exchange for lease liability	226	6,948
Property and equipment purchases included in accounts payable and accrued liabilities	2,448	52	55
Issuance of common stock warrants in connection with debt financing			$ 104
Transfer of fixed assets to inventory	$ 413	$ 119

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Basis of Presentation

1. Organization and Basis of Presentation

Shockwave Medical, Inc. (the “Company”) was incorporated on June 17, 2009. The Company is primarily engaged in the development of Intravascular Lithotripsy (“IVL”) technology for the treatment of calcified plaque in patients with peripheral vascular, coronary vascular and heart valve disease. Built on a balloon catheter platform, the IVL technology uses lithotripsy to disrupt both superficial and deep vascular calcium, while minimizing soft tissue injury, and an integrated angioplasty balloon to dilate blockages at low pressures, restoring blood flow.

In 2016, the Company began commercial and manufacturing operations, and began selling catheters based on the IVL technology. The Company’s headquarters are in Santa Clara, California. The Company is located and operates primarily in the United States and has subsidiaries in Germany, the United Kingdom and Japan.

Initial Public Offering

On March 11, 2019, the Company completed an initial public offering (“IPO”) of its common stock. As part of the IPO, the Company issued and sold 6,555,000 shares of its common stock, which included 855,000 shares sold pursuant to the exercise of the underwriters’ over-allotment option, at a public offering price of $17.00 per share. The Company received net proceeds of approximately $99.9 million from the IPO, after deducting underwriters’ discounts and commissions. Prior to the completion of the IPO, all shares of Series A, A-1, B, C and D convertible preferred stock then outstanding were converted into 18,670,259 shares of common stock on a one-to-one basis.

In addition, on the completion of the IPO, all the Company’s outstanding preferred stock warrants were converted into 54,903 common stock warrants, which resulted in the reclassification of the convertible preferred stock warrant liability to additional paid-in capital. Furthermore, 101,744 shares of common stock were issued upon net exercise of warrants at the time of the IPO.

Concurrently with the IPO, the Company issued 588,235 shares of its common stock in a private placement for net proceeds of $10.0 million.

Public Offerings

On November 15, 2019, the Company completed an underwritten public offering of 2,854,048 shares of its common stock, including 372,267 shares sold pursuant to the underwriters’ exercise of their option to purchase additional shares, at a public offering price of $36.25 per share. The Company received net proceeds of $96.7 million from the follow-on offering after deducting underwriters’ discounts and commissions. On June 19, 2020, the Company completed an underwritten offering of 1,955,000 shares of its common stock, including 255,000 shares sold pursuant to the underwriters’ exercise of their option to purchase additional shares, at a public offering price of $45.75 per share. Upon completion of the June 2020 offering, the Company received net proceeds of $83.4 million, after deducting underwriting discounts and commissions and offering expenses.

Liquidity

As of December 31, 2020, the Company had cash, cash equivalents and short-term investments of $202.4 million, which are available to fund future operations. The Company believes that its cash, cash equivalents, and short-term investments as of December 31, 2020, will be sufficient for the Company to continue as a going concern for at least 12 months from the date the consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include, but are not limited to the valuation of inventory, the allowance for doubtful accounts, the fair value of stock options, recoverability of the Company’s net deferred tax assets, and related valuation allowance and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows:

	December 31, 2020		December 31, 2019
	(in thousands)
Cash and cash equivalents	$	50,423	$	139,045
Restricted cash		1,450		1,450
Total cash, cash equivalents, and restricted cash	$	51,873	$	140,495

Restricted cash as of December 31, 2020 and 2019 relates to letters of credit established for real property leases entered into in May 2018 and December 2019 relating to buildings housing the Company’s corporate offices and manufacturing facilities, and is recorded as other assets on the consolidated balance sheets.

Short-Term Investments

Short-term investments have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. The Company determines the appropriate classification of its investments in debt securities at the time of purchase. Available-for-sale securities with original maturities beyond three months at the date of purchase are classified as current based on their availability for use in current operations.

The Company evaluates, on a quarterly basis, its marketable securities for potential impairment. For marketable securities in an unrealized loss position, the Company assesses whether such declines are due to credit loss based on factors such as changes to the rating of the security by a ratings agency, market conditions and supportable forecasts of economic and market conditions, among others. If credit loss exists, the Company assess whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable security before recovery of its amortized cost basis. If either condition is met, the security’s amortized cost basis is written down to fair value and is recognized through other income, net.

If neither condition is met, declines as a result of credit losses, if any, are recognized as an allowance for credit loss, limited to the amount of unrealized loss, through other income, net. Any portion of unrealized loss that is not a result of a credit loss, is recognized in other comprehensive income. Realized gains and losses, if any, on marketable securities are included in other income, net. The cost of investments sold is based on the specific-identification method. Interest on marketable securities is included in other income, net.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, investments and trade receivables. Risks associated with cash, cash equivalents and restricted cash are mitigated by banking with creditworthy institutions and the Company’s investments have investment grade ratings when purchased. The Company performs ongoing evaluations of its customers using its historical collection experience, current and future economic market conditions and a review of the current aging status and financial condition of its customers, and generally does not require collateral.

Concentration of Customers

For the years ended December 31, 2020, 2019 and 2018 no customer accounted for 10% of the Company’s revenue. There was one customer which accounted for 15% of the Company’s accounts receivable as of December 31, 2020. There was one customer which accounted for 11% of the Company’s accounts receivable as of December 31, 2019.

Fair Value of Financial Instruments

The Company’s cash and cash equivalents, restricted cash, short-term investments, accounts receivable, accounts payable and accrued liabilities approximate their fair value due to their short maturities. Management believes that its term notes bear interest at the prevailing market rates for instruments with similar characteristics; accordingly, the carrying value of this instrument approximates its fair value.

The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels:

Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

Level 2 – Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Accounts Receivable and Allowance for Doubtful Accounts

The Company adopted Accounting Standards Update (“ASU”) 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, effective January 1, 2020 using the modified retrospective method. The adoption of this standard did not have a cumulative effect on opening accumulated deficit as of January 1, 2020 and did not have a material impact on the Company’s financial statements. Prior period amounts have not been adjusted and continue to be reported in accordance with our historic accounting prior to the adoption of ASU 2016-13.

Accounts receivable are recorded at invoice value, net of any allowance for credit losses. The Company’s expected loss allowance methodology for receivables is developed using its historical collection experience, current and future economic market conditions and a review of the current aging status and financial condition of its customers. Specific allowance amounts are established to record the appropriate allowance for customers that have an identified risk of default. General allowance amounts are established based upon our assessment of expected credit losses for our receivables by aging category. Balances are written off when they are ultimately determined to be uncollectible.

The following table summarizes the activity in the allowance for doubtful accounts:

	For the Year Ended December 31,
	2020			2019			2018
	(in thousands)
Beginning balance	$	194		$	76		$	—
Amounts charged to costs and expenses		205			121			77
Write-offs		(19	)		(3	)		(1	)
Ending balance	$	380		$	194		$	76

Inventory

Inventory is stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) and net realizable value. Inventory costs include direct materials, direct labor and normal manufacturing overhead. Prior to achieving normal capacity, excess capacity costs are expensed in cost of product revenue as period costs. Finished goods that are used for research and development are expensed as consumed. Provisions for slow-moving, excess or obsolete inventories are recorded when required to reduce inventory values to their estimated net realizable values based on product life cycle, development plans, product expiration or quality issues.

Property and Equipment

Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized over the lesser of their useful life or the remaining life of the lease. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Maintenance and repairs are charged to operations as incurred.

Impairment of Long-Lived Assets

The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future net undiscounted cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. The Company has not identified any such impairment losses to date.

Revenue

The Company records product revenue primarily from the sale of its IVL catheters. The Company sells its products to hospitals, primarily through direct sales representatives, as well as through distributors in selected international markets. Additionally, a significant portion of the Company’s revenue is generated through a consignment model under which inventory is maintained at hospitals.

Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company elected to exclude taxes assessed by a governmental authority on revenue-producing transactions from the transaction price.

For products sold through direct sales representatives, control is transferred upon delivery to customers. For products sold to distributors internationally and certain customers that purchase stocking orders in the United States, control is transferred upon shipment or delivery to the customer’s named location, based on the contractual shipping terms. For consignment inventory, control is transferred at the time the catheters are consumed in a procedure. The Company elected to account for shipping and handling activities that occur after the customer has obtained control as a fulfillment activity, and not a separate performance obligation.

The Company may provide for the use of an IVL generator and connector cable under an agreement to customers at no charge to facilitate use of the IVL catheters. These agreements do not contain contractually enforceable minimum commitments and are generally cancellable by either party with 30 days’ notice.

Research and Development Costs

Research and development costs, including new product development, regulatory compliance, and clinical research are expensed as incurred.

Accrued Research and Development Costs

The Company accrues liabilities for estimated costs of research and development activities conducted by its third-party service providers, which include the conduct of preclinical and clinical studies. The estimated costs of research and development activities are recorded based upon the estimated amount of services provided but not yet invoiced, and these costs are included in accrued liabilities on the consolidated balance sheets and within research and development expense on the consolidated statements of operations and comprehensive loss.

These costs are accrued for based on factors such as estimates of the work completed and budget provided and in accordance with agreements established with third-party service providers. Significant judgments and estimates are made in determining the accrued liabilities balance in each reporting period. Accrued liabilities are adjusted as actual costs become known. There have not been any material differences between accrued costs and actual costs incurred since the Company’s inception.

Stock-Based Compensation

The Company accounts for share-based payments at fair value. The fair value of stock options is measured using the Black-Scholes option-pricing model. For share-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date for stock-based compensation awards is the date of grant and the expense is recognized on a straight-line basis, over the vesting period. The Company accounts for forfeitures as they occur.

Leases

The Company adopted ASU No. 2016-02, Leases (Topic 842) using the modified retrospective approach with a cumulative-effect adjustment as of January 1, 2019. Results for reporting periods beginning after January 1, 2019 are presented under Topic 842. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840).

For its long-term operating lease, the Company recognized a right-of-use asset and a lease liability on its consolidated balance sheet. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would have to pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The lease term at the commencement date is determined by considering whether renewal options and termination options are reasonably assured of exercise.

Rent expense for the operating lease is recognized on a straight-line basis over the lease term and is included in operating expenses on the consolidated statements of operations and comprehensive loss. Variable lease payments include lease operating expenses.

The Company elected the practical expedients to exclude from its balance sheets recognition of leases having a term of 12 months or less (short-term leases) and to not separate lease components and non-lease components for its long-term real estate leases.

Defined Contribution Plan

The Company has a defined contribution retirement savings plan under Section 401(k) of the Internal Revenue Code. This plan allows eligible employees to defer a portion of their annual compensation on a pre-tax basis. The Company is authorized to make matching contributions. During 2020, the Company made matching contributions up to $3,000 of an employee’s eligible deferred compensation. The Company recognized expense related to its contributions to the plan of $1.1 million for the year-ended December 31, 2020. The Company did not make such contributions for the year ended December 31, 2019 or 2018.

Comprehensive Loss

Comprehensive loss is comprised of net loss and changes in unrealized gains and losses on the Company’s available-for-sale investments.

Foreign Currency

The functional currency of the Company’s foreign subsidiaries is the U.S. Dollar. Accordingly, all monetary assets and liabilities of the subsidiary are remeasured at the current exchange rate at the end of the period, nonmonetary assets and liabilities are remeasured at historical rates, and revenue and expenses are remeasured at average exchange rates during the period. There were net foreign currency transaction gains of $261,000 and $56,000 for the years ended December 31, 2020 and 2019, respectively. In December 31, 2018, there were net foreign currency transaction losses of $46,000.

Net Loss Per Share

Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration of potential dilutive shares of common stock. The unvested portion of early exercised stock options are excluded from the computation of weighted-average shares as the continuing vesting of such shares is contingent on the holders’ continued service to the Company. Because the Company was in a loss position for the period presented, basic net loss per share is the same as diluted net loss per share since the effects of potentially dilutive securities are antidilutive.

Income Taxes

The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the net deferred tax assets have been fully offset by a valuation allowance.

The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of provision for income taxes.

Segment Reporting

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its Chief Executive Officer. The Company has determined that it operates in one segment. The Company’s long-lived assets are all held in the United States with the exception of certain equipment on loan to customers held internationally, which was not material for the years-ended December 31, 2020 and 2019.

Recently Adopted Accounting Pronouncements

Effective January 1, 2020, the Company adopted ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires measurement and recognition of expected credit losses for most financial assets and certain other instruments. Unrealized losses on available-for-sale debt securities that are attributed to credit risk are recorded through earnings rather than to other comprehensive income. Credit losses relating to available-for-sale debt securities are now recorded through an allowance for credit losses. The adoption of this guidance did not result in a cumulative effect adjustment as of the date of the adoption.

In addition, Topic 326 also provides new guidance related to the measurement of expected credit losses on the Company’s allowance for bad debt for accounts receivable, which is estimated upon assessment of various factors including historical collection experience, current and future economic market conditions and a review of the current aging status and financial condition of the Company’s customers. As of March 31, 2020, the Company considered the current and expected future economic and market conditions surrounding the COVID-19 pandemic and increased the overall reserve for credit losses by $0.2 million in response to an assessment of the evolving credit environment under the COVID-19 pandemic. The Company continued to monitor our customer collections and credit risk, however, no additional material changes to the allowance for doubtful accounts, subsequent to March 31, 2020, were recorded for the year-ended December 31, 2020. The Company will continue to update its estimate of credit losses from accounts receivable in future periods in response to the uncertainties caused by the COVID-19 pandemic.

Recent Accounting Pronouncements Not Yet Adopted

In November 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), which simplifies the accounting for income taxes, primarily by eliminating certain exceptions to the guidance in ASC 740. This ASU is effective for fiscal periods beginning after December 15, 2020. The Company is currently evaluating the effect of adopting this standard but does not expect the adoption of this standard to have a material impact on its consolidated financial statements. ASU No. 2019-12 became effective for the Company upon adoption on January 1, 2021.

Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

3. Financial Instruments and Fair Value Measurements

The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy:

	December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	126,363	$	—	$	—	$	126,363
Money market funds		35,053		—		—		35,053
Commercial paper		—		31,968		—		31,968
Total assets	$	161,416	$	31,968	$	—	$	193,384

	December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	43,245	$	—	$	—	$	43,245
Money market funds		29,386		—		—		29,386
Reverse repurchase agreements		—		10,000		—	$	10,000
Commercial paper		—		6,958		—	$	6,958
Corporate bonds		—		8,096		—	$	8,096
Total assets	$	72,631	$	25,054	$	—	$	97,685

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Cash Equivalents and Short-Term Investments

12 Months Ended

Dec. 31, 2020

Cash And Cash Equivalents [Abstract]

Cash Equivalents and Short-Term Investments

4. Cash Equivalents and Short-Term Investments

The following is a summary of the Company’s cash equivalents and short-term investments:

	December 31, 2020
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	126,354	$	11	$	(2	)	$	126,363
Money market funds		35,053		—		—			35,053
Commercial paper		31,968		—		—			31,968
Total	$	193,375	$	11	$	(2	)	$	193,384
Reported as:
Cash equivalents								$	41,453
Short-term investments									151,931
Total								$	193,384

	December 31, 2019
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	43,219	$	27	$	(1	)	$	43,245
Money market funds		29,386		—		—			29,386
Reverse repurchase agreements		10,000		—		—			10,000
Commercial paper		6,958		—		—			6,958
Corporate bonds		8,087		9		—			8,096
Total	$	97,650	$	36	$	(1	)	$	97,685
Reported as:
Cash equivalents								$	41,381
Short-term investments									56,304
Total								$	97,685

At December 31, 2020, the remaining contractual maturities for available-for-sale securities were less than one year. For the year ended December 31, 2020, the Company recognized $21,000 in realized gains on cash equivalents and short-term investments. There were no material realized gains or losses on cash equivalents and short-term investments for the years ended December 31, 2019 and 2018.

Balance Sheet Components

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

5. Balance Sheet Components

Inventory

Inventory consists of the following:

	December 31,
	2020		2019
	(in thousands)
Raw material	$	4,995	$	2,501
Work in progress		6,051		1,364
Finished goods		16,952		6,642
Consigned inventory		1,861		1,567
Total inventory	$	29,859	$	12,074

Property and Equipment, Net

Property and equipment, net consists of the following:

	December 31,
	2020			2019
	(in thousands)
Equipment	$	3,794		$	3,759
Equipment on loan to customers		1,756			1,495
Office furniture		157			76
Software		175			97
Leasehold improvements		5,808			1,329
Construction in progress		7,800			553
Property and equipment, gross		19,490			7,309
Less accumulated depreciation and amortization		(3,128	)		(2,399	)
Total property and equipment, net	$	16,362		$	4,910

Depreciation and amortization expense amounted to $1.9 million, $1.3 million and $0.7 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2020		2019
	(in thousands)
Accrued employee compensation	$	10,885	$	8,139
Accrued research and development costs		3,057		3,090
Accrued asset purchases		2,527		—
Accrued professional services		1,325		804
Other		2,148		1,744
Total accrued liabilities	$	19,942	$	13,777

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Operating Leases

In May 2018, the Company entered into a lease agreement for office, laboratory, and manufacturing space located at 5403 Betsy Ross Drive in Santa Clara, California, which consists of approximately 35,000 square feet (the “5403 Lease”). The term of the 5403 Lease commenced in September 2018 and ends in August 2022. In connection with the 5403 Lease, the Company maintains a letter of credit for the benefit of the landlord in the amount of $0.5 million, which is secured by restricted cash recorded as other assets on the consolidated balance sheets. In connection with the 5403 Lease, the Company has an operating lease right-of-use asset of $1.3 million as of December 31, 2020 and an aggregate lease liability of $1.4 million on its consolidated balance sheet. The remaining lease term is one year and eight months.

In December 2019, the Company entered into a lease agreement (i) for additional office, laboratory and manufacturing space located at 5353 Betsy Ross Drive in Santa Clara, California, which consists of approximately 50,200 square feet (the “5353 Lease”); and (ii) to modify the terms of the 5403 Lease. The 5403 Lease will continue in its existing terms (and with no changes to its terms, including its base rent) until its expiration on August 31, 2022, at which point the leased space under the 5403 Lease will become subject to the terms of the 5353 Lease. The initial term of the 5353 Lease began in December 2019 and is for 96 months, with an option by the Company to extend for an additional five years on either or both of the 5403 and 5353 Betsy Ross buildings. The base rent of the first floor of the premises for the 5353 Betsy Ross building shall be abated for the first 19 months, and the base rent for the second floor of the 5353 Betsy Ross building shall be abated for the first four months. The landlord provided the Company with a tenant improvement allowance of up to $1.8 million for both 5403 and 5353 Betsy Ross buildings. In connection with the 5353 Lease, the Company provided an initial security deposit of $1.0 million in the form of a letter of credit, which is secured by restricted cash recorded as other assets on the consolidated balance sheets. While this amount will increase to $1.5 million on September 1, 2022 when the office, laboratory and manufacturing space of the 5403 Lease is included under the terms of the 5353 Lease, the letter of credit will be reduced annually from and after September 1, 2022 until the expiration of the 5353 Lease. In connection with the lease of the 5353 Betsy Ross building, the Company has recorded an operating lease right-of-use asset of $6.1 million as of December 31, 2020 and an aggregate lease liability of $6.8 million on its consolidated balance sheet. The remaining lease term is six years and eleven months.

The Company also leases vehicles for use by employees. In connection with the vehicle leases, the Company has an operating lease right-of-use asset and an aggregate lease liability of $0.2 million as of December 31, 2020 on its consolidated balance sheet. The weighted average remaining lease term for these vehicle leases is two years and four months.

The weighted average incremental borrowing rate used to measure the operating lease liability is 6.98%. As of December 31, 2020, the Company has no finance leases.

Short-term leases are leases having a term of 12 months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases.

The following are minimum future rental payments owed under these agreements which have commenced as of December 31, 2020:

	(in thousands)
2021	$	1,946
2022		2,123
2023		1,529
2024		1,546
2025		1,594
Thereafter		3,232
Total minimum lease payments	$	11,970
Less: imputed interest		(3,609	)
Total lease liability	$	8,361

The following are minimum future rental payments owed for the modified 5403 Betsy Ross Lease which has not yet commenced as of December 31, 2020:

	(in thousands)
2021	$	—
2022		345
2023		1,044
2024		1,078
2025		1,112
Thereafter		2,253
Total minimum lease payments	$	5,832

Operating lease cost for the years ended December 31, 2020 and 2019 was $2.2 million and $1.2 million, respectively. Rent expense for the year ended December 31, 2018 was $0.9 million.

Term Notes

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Term Notes

7. Term Notes

Loan and Security Agreement

In February 2018, the Company entered into a Loan and Security Agreement with Silicon Valley Bank (the “Loan and Security Agreement”). The terms of the Loan and Security Agreement included a term loan of $15.0 million and a revolving line of credit of $2.0 million. The term loan was available in two tranches, of which the first tranche of $10.0 million was funded in June 2018 and the second tranche of $5.0 million was funded in December 2018.

The term loan accrued interest at a floating per annum rate equal to the greater of (a) the Wall Street Journal prime rate minus 1.75% and (b) 2.75%. There was a final payment equal to 6.75% of the original aggregate principal amount, or $1.0 million, of the term loan advances, which was being accrued over the term of the loan using the effective-interest method.

In connection with the execution of the Loan and Security Agreement, the Company issued warrants to purchase 34,440 shares of the Company’s common stock. Upon issuance, the fair value of the warrants of $0.1 million was recorded as a debt issuance cost. The debt issuance cost will be amortized to interest expense, net over the term of the loan.

In February 2020, the Company entered into a First Amendment to its Loan and Security Agreement (the “Amended Credit Facility”) to, among other things, refinance its existing term loan, which is accounted for as a modification of the Loan and Security Agreement. Under the Amended Credit Facility, the existing revolving line of credit of $2.0 million was terminated and the termination fee of less than $0.1 million was waived. The Amended Credit Facility provides the Company with a supplemental term loan in the amount of $16.5 million. After repayment of the outstanding amount of the term loan, the Company received net proceeds of $3.3 million, which reflects an additional $4.3 million in principal as of the date of the modification less the final balloon payment fee of $1.0 million. The principal amount outstanding under the supplemental term loan accrues interest at a floating per annum rate equal to the greater of (a) the Prime Rate minus 1.25% and (b) 3.5%. The interest rate was 3.5% as of December 31, 2020.

The supplemental term loan matures on December 1, 2023. The Amended Credit Facility provides an interest-only payment period which will end on (a) June 30, 2021, if the Company’s revenue for the trailing 12-month period ended June 30, 2021 is not at least 75% of the Company’s projections; (b) December 31, 2021, if the Company achieves the financial performance target referred to in clause (a), but does not obtain premarket approval of the Company’s C²catheters from the FDA by such date and/or the Company’s trailing 12-month revenue for the period ending December 31, 2021 is not at least 75% of the Company’s projections; or (c) June 30, 2022, if the Company achieves the milestones referred to in clauses (a) and (b).

The additional final payment for the Amended Credit Facility is $1.6 million, which is currently being accrued over the term of the supplemental term loan using an effective interest rate that reflects the revised cash flows of the modified term loan.

During the years ended December 31, 2020, 2019 and 2018 the Company recorded interest expense of $0.6 million, $0.5 million and $0.2 million, respectively. Debt discount amortized as interest expense was $0.6 million, $0.4 million and $0.2 million for the years ended December 31, 2020, 2019 and 2018, respectively.

The supplemental term loan is secured by all of the Company’s assets, excluding intellectual property and certain other assets. The loan contains customary affirmative and restrictive covenants, including with respect to the Company’s ability to enter into fundamental transactions, incur additional indebtedness, grant liens, pay any dividend or make any distributions to its holders, make investments, merge or consolidate with any other person or engage in transactions with the Company’s affiliates, but does not include any financial covenants.

Long-term debt and net premium balances are as follows:

	December 31,
	2020			2019
	(in thousands)
Principal amount of term note	$	16,500		$	13,334
Net premium associated with accretion of final payment and other debt issuance costs		119			485
Term note, current and noncurrent		16,619			13,819
Less term note, current portion		(3,300	)		(6,667	)
Term note, noncurrent portion	$	13,319		$	7,152

Future minimum payments of principal and estimated payments of interest on the Company’s outstanding variable rate borrowings as of December 31, 2020 are as follows:

Year ending December 31:	(in thousands)
2021	$	3,861
2022		6,961
2023		8,294
Total future payments		19,116
Less amounts representing interest		(1,048	)
Less final payment		(1,568	)
Total principal amount of term note payments	$	16,500

Convertible Preferred Stock and Stockholders’ Equity (Deficit)

12 Months Ended

Dec. 31, 2020

Stockholders Equity [Abstract]

Convertible Preferred Stock and Stockholders’ Equity (Deficit)

8. Convertible Preferred Stock and Stockholders’ Equity (Deficit)

Convertible Preferred Stock

Immediately prior to the closing of the Company’s IPO, 18,670,259 shares of outstanding convertible preferred stock converted into 18,670,259 shares of common stock.

Preferred Stock

The Company’s amended and restated certificate of incorporation, which became effective upon the completion of the IPO, authorizes 5,000,000 shares of preferred stock, of which no shares were issued or outstanding as of December 31, 2020 and 2019.

Preferred Stock Warrants

Upon the closing of the IPO, all of the outstanding convertible preferred stock warrants were converted into 54,903 common stock warrants, which resulted in the reclassification of the convertible preferred stock warrant liability of $0.8 million to additional paid-in capital. In April 2019, all of these common stock warrants were net exercised into 49,321 shares of common stock. There were no preferred stock warrants outstanding of December 31, 2020 and 2019.

Common Stock Warrants

Upon the IPO, 91,446 common stock warrants held by related parties were net exercised based on the IPO price of $17.00 per share into 79,632 shares of common stock.

In February 2018, in connection with the execution of a Loan and Security Agreement with Silicon Valley Bank for a term loan and revolving line of credit, the Company issued warrants to purchase shares of the Company’s common stock. In April 2019, all of these common stock warrants were net exercised into 29,887 shares of common stock. There were no common stock warrants outstanding of December 31, 2020 and 2019.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

9. Stock-Based Compensation

Total stock-based compensation was as follows:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
Cost of product revenue	$	496	$	268	$	67
Research and development		2,464		943		235
Sales and marketing		3,478		972		294
General and administrative		3,912		1,463		701
Total stock-based compensation	$	10,350	$	3,646	$	1,297

Stock-based compensation of $316,000 was capitalized into inventory for the year ended December 31, 2020. No material stock-based compensation was capitalized into inventory for the years ended December 31, 2019 and 2018. Stock-based compensation capitalized into inventory is recognized as cost of product revenue when the related product is sold.

Determination of Fair Value

The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions:

	Year Ended December 31,
	2019	2018
Expected term (in years)	6.08	6.08
Expected volatility	42.4%-42.9%	40.8%-41.9%
Risk-free interest rate	2.4%-2.6%	2.5%-3.1%
Expected dividend yield	0%	0%

The fair value of each stock option grant was determined by the Company using the methods and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment and estimation by management.

Expected Term—The expected term represents the period that stock-based awards are expected to be outstanding. The Company’s historical share option exercise information is limited due to a lack of sufficient data points, and did not provide a reasonable basis upon which to estimate an expected term. The expected term for option grants is therefore determined using the simplified method. The simplified method deems the expected term to be the midpoint between the vesting date and the contractual life of the stock-based awards.

Expected Volatility—Since the Company has limited trading history for its common stock due to its short trading history, the expected volatility was estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their similar size, stage in the life cycle or area of specialty.

Risk-Free Interest Rate—The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the stock-based awards’ expected term.

Expected Dividend Yield—The expected dividend yield is zero as the Company has not paid nor does it anticipate paying any dividends on its common stock in the foreseeable future.

The Company has elected to recognize forfeitures of share-based payment awards as they occur.

2009 Equity Incentive Plan and 2019 Equity Incentive Plan

On June 17, 2009, the Company adopted the 2009 Equity Incentive Plan (the “Plan”) under which the Company’s board of directors (the “Board”) may issue stock options to employees, directors and consultants.

In February 2019, the Company adopted the 2019 Stock Option and Incentive Plan (the “2019 Plan”), which became effective in connection with the IPO. As a result, effective as of March 6, 2019, the Company may not grant any additional awards under the 2009 Plan. The 2009 Plan will continue to govern outstanding equity awards granted thereunder. The Company initially reserved 2,000,430 shares of common stock for the issuance of a variety of awards under the 2019 Plan, including stock options, stock appreciation rights, awards of restricted stock and awards of restricted stock units. In addition, the number of shares of common stock reserved for issuance under the 2019 Plan will automatically increase on the first day of January for a period of up to ten years, which commenced on January 1, 2020, in an amount equal to 3% of the total number of shares of the Company’s common stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors.

The Board has the authority to determine to whom options will be granted, the number of shares, the term and the exercise price. If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the Board. Options granted under the Plan have a term of up to 10 years and generally vest over a 4 year period with a straight-line vesting and a 25% one year cliff. As of December 31, 2020, the Company had reserved 2,689,624 shares of common stock for issuance under the 2019 Plan.

Stock Options

Activity under the 2009 Plan and 2019 Plan is set forth below:

	Shares Available for Grant			Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Term	Aggregate Intrinsic Value
									(in years)	(in thousands)
Balance, December 31, 2017		426,370			3,108,604		$	2.81	8.03	$	3,647
Awards authorized		691,503			—
Options granted		(1,015,963	)		1,015,963			5.25
Options exercised		—			(197,820	)		2.20
Options cancelled		290,389			(290,389	)		3.42
Balance, December 31, 2018		392,299			3,636,358		$	3.54	7.79	$	11,267
Awards authorized		2,000,430			—
Options expired		(287,600	)		—
Options granted		(442,858	)		442,858			14.69
Options exercised		—			(722,242	)		3.10
Options cancelled		41,973			(41,973	)		3.85
Balance, December 31, 2019		1,704,244			3,315,001		$	5.08	7.28	$	128,744
Awards authorized		943,345			—
Options exercised		—			(1,185,764	)		3.64
Options cancelled		42,035			(42,035	)		4.45
Balance, December 31, 2020		2,689,624			2,087,202		$	5.92	6.77	$	204,137
Vested and exercisable, December 31, 2020					1,360,650		$	4.63	6.36	$	134,825
Vested and expected to vest, December 31, 2020					2,087,202		$	5.92	6.77	$	204,137

There were no options granted during the year ended December 31, 2020. The weighted-average grant date fair value of options granted during the year ended December 31, 2019 and 2018 was $6.58 and $2.56 per share, respectively. The total grant date fair value of options vested was $2.3 million, $1.9 million and $1.6 million for the years ended December 31, 2020, 2019 and 2018, respectively.

As of December 31, 2020, total unrecognized stock-based compensation related to unvested stock options was $2.5 million, which the Company expects to recognize over a remaining weighted-average period of 1.3 years.

Restricted Stock Units

Restricted stock units (“RSUs”) are share awards that entitle the holder to receive freely tradable shares of the Company’s common stock upon vesting. The RSUs cannot be transferred and the awards are subject to forfeiture if the holder’s employment terminates prior to the release of the vesting restrictions. The RSUs generally vest over a four-year period with a 25% one-year cliff or over a three-year period in equal amounts on a semi-annual basis, provided the employee remains continuously employed with the Company. The fair value of the RSUs is equal to the closing price of the Company’s common stock on the grant date.

RSU activity under the 2019 Plan is set forth below:

	Number of Shares			Weighted- Average Grant Date Fair Value Per Share
Balance, December 31, 2018		—		$	—
RSUs granted		288,170			38.28
RSUs forfeited		(5,600	)		40.01
RSUs vested		(1,666	)		59.79
Balance, December 31, 2019		280,904		$	38.12
RSUs granted		687,223			51.34
RSUs forfeited		(38,650	)		41.55
RSUs vested		(69,900	)		38.46
Balance, December 31, 2020		859,577		$	48.50

The total grant date fair value of RSUs vested for the years ended December 31, 2020 and 2019 was $2.7 and $0.1 million, respectively. There were no RSUs granted prior to 2019. As of December 31, 2020, there was $35.3 million of unrecognized stock-based compensation expense related to RSUs to be recognized over a weighted-average period of 3.1 years.

Employee Share Purchase Plan (ESPP)

In February 2019, the Company adopted the 2019 Employee Stock Purchase Plan (“ESPP”), which became effective as of March 6, 2019. The Company initially reserved 300,650 shares of the Company’s common stock for purchase under the ESPP. In addition, the number of shares of common stock reserved for issuance under the ESPP will automatically increase on the first day of January for a period of up to ten years, which commenced on January 1, 2020, in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Board.

Each offering to the employees to purchase stock under the ESPP will begin on each September 1 and March 1 and will end on the following February 28 or 29 and August 30, respectively. On each purchase date, which falls on the last date of each offering period, ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of (1) the fair market value per share of the common stock on the offering date or (2) the fair market value of the common stock on the purchase date. The occurrence and duration of offering periods under the ESPP are subject to the determinations of the Compensation Committee of the Board, in its sole discretion.

The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. The Company recorded $786,000 and $255,000 of stock-based compensation expense related to the ESPP for the years ended December 31, 2020 and 2019, respectively.

	Year Ended December 31,	Year Ended December 31,
	2020	2019
Expected term (in years)	0.5	0.5
Expected volatility	44.31%-74.03%	76.93%
Risk-free interest rate	0.12%-0.3%	1.89%
Expected dividend yield	0%	0%

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

The following table presents income (loss) before income taxes for the periods presented:

	December 31,
	2020			2019			2018
	(in thousands)
Domestic	$	(65,957	)	$	(51,179	)	$	(41,145	)
Foreign		338			132			81
Total loss before income taxes	$	(65,619	)	$	(51,047	)	$	(41,064	)

Current income tax provision consists of the following:

	December 31,
	2020		2019		2018
	(in thousands)
Domestic	$	3	$	—	$	3
Foreign		77		62		35
Total current income tax provision	$	80	$	62	$	38

The components of the deferred tax assets are as follows:

	December 31,
	2020			2019
	(in thousands)
Deferred tax assets:
Net operating loss carryovers	$	73,453		$	49,862
Fixed and intangible assets		718			450
Accruals and reserves		2,245			1,619
Stock-based compensation		2,060			780
Research and development credits		3,379			2,336
Contributions		42			20
Lease liability		2,004			2,135
Total deferred tax assets		83,901			57,202
Less valuation allowance		(82,087	)		(55,085	)
Gross deferred tax assets		1,814			2,117
Deferred tax liabilities:
Right-of-use-assets		(1,814	)		(2,117	)
Gross deferred tax liabilities		(1,814	)		(2,117	)
Total net deferred tax assets	$	—		$	—

Reconciliation of the statutory federal income tax to the Company’s effective tax is as follows:

	December 31,
	2020			2019			2018
	(in thousands)
Income tax benefit at federal statutory rate	$	(13,780	)	$	(10,720	)	$	(8,624	)
State and local income taxes net of federal tax benefit		(9	)		(9	)		3
Foreign tax rate differential		6			35			11
Change in valuation allowance		27,990			14,470			8,497
Stock-based compensation		(13,425	)		(3,403	)		123
R&D tax credits		(611	)		(354	)		(313	)
Other		(91	)		43			341
Total current income tax provision	$	80		$	62		$	38

Due to the uncertainties surrounding the realization of deferred assets through future taxable income, the Company has provided a full valuation allowance and, therefore, no benefit has been recognized for the net operating loss and other deferred tax assets. The valuation allowance increased by $27.0 million, $22.8 million and $10.0 million during the years ended December 31, 2020, 2019 and 2018, respectively.

As of December 31, 2020, the Company had net operating loss carryforwards available to reduce future federal, California and other state income of $301.9 million, $52.4 million and $123.7 million, respectively. The federal net operating loss carryforwards of $80.8 million and $221.1 million begin expiring in 2030 and never expire respectively, the California net operating loss carryforwards begin expiring in 2031 and other state net operating loss carryforwards begin expiring in various years, starting in 2029.

As of December 31, 2020, the Company had research and development credit carryforwards of $4.0 million for federal income tax purposes and $3.5 million for California state income tax purposes available to reduce future taxable income, if any. The federal research and development credit carryforwards expire beginning 2033 and California credits can be carried forward indefinitely.

Utilization of the net operating loss carryforward may be subject to an annual limitation due to the ownership change provided by the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization. The Company has not prepared a Section 382 study to date to determine if a greater than 50% ownership change has occurred and to determine the annual Section 382 limitation if applicable. Thus, the Company has not determined if there are any limitations on the Company’s ability to utilize its net operating losses in the future and if any reduction in the net operating loss deferred tax assets is required until such study is performed. Upon completion of a 382 study, to the extent that our net operating losses are reduced due to ownership changes, the impact would result in a reduction of the net operating loss deferred tax assets offset by a reduction in the valuation allowance.

Uncertain Tax Positions

The activity related to the gross amount of unrecognized tax benefits is as follows:

	December 31,
	2020			2019		2018
	(in thousands)
Beginning balance	$	2,586		$	1,896	$	893
Additions (Reductions) based on tax positions related to prior years		(3	)		—		394
Additions based on tax positions related to current years		1,163			690		609
Balance at end of year	$	3,746		$	2,586	$	1,896

If recognized, gross unrecognized tax benefits would not have an impact on the Company’s effective tax rate due to the Company’s full valuation allowance position. While it is often difficult to predict the final outcome of any particular uncertain tax position, the Company does not believe that the amount of gross unrecognized tax benefits will change significantly in the next twelve months.

It is the Company’s policy to include penalties and interest expense related to income taxes as a component of the income tax provision as necessary. The Company determined that no accrual for interest and penalties was required as of December 31, 2020.

The Company is subject to taxation in the United States, Germany, and Japan. The Company’s income tax returns since inception remain subject to examination by U.S. federal and most state tax authorities due to its net operating loss. The income tax returns of Shockwave Medical GmbH for the 2016 through 2020 tax years remain subject to examination by the German taxing authorities and the income tax returns of Shockwave Medical Japan KK for the 2020 tax year will be subject to examination by the Japanese taxing authorities once filed. The Company is not currently under audit with either the IRS, foreign, or any state or local jurisdictions, nor has it been notified of any other potential future income tax audit. The federal and California statute of limitations remains open for three and four years, respectively, from the date of utilization of any net operating loss or credits.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

11. Net Loss Per Share

The following outstanding potentially dilutive common stock equivalents have been excluded from the calculation of diluted net loss per share for the period presented due to their anti-dilutive effect:

	December 31,
	2020		2019		2018
	(in thousands)
Convertible preferred stock on an as-converted basis		—		—		18,670,328
Common stock options issued and outstanding		2,087,202		3,315,001		3,636,358
Restricted stock units		859,577		280,904		—
Employee stock purchase plan		15,251		16,420		—
Early exercised options subject to future vesting		—		—		13,422
Convertible preferred stock warrants		—		—		54,903
Common stock warrants		—		—		176,218
Total		2,962,030		3,612,325		22,551,229

Revenue

12 Months Ended

Dec. 31, 2020

Disaggregation Of Revenue [Abstract]

Revenue

12. Revenue

Disaggregation of revenue

The following table represents the Company’s product revenue based on product line:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
Peripheral	$	41,994	$	26,325	$	8,828
Coronary		24,586		15,621		3,210
Other		1,209		981		225
Product revenue	$	67,789	$	42,927	$	12,263

Peripheral product revenue encompasses sales of the Company’s M⁵ and S⁴ IVL catheters. Coronary product revenue encompasses sales of the Company’s C² catheters. Other product revenue encompasses sales of the Company’s generators and related accessories.

The following table represents the Company’s product revenue based on the location to which the product is shipped:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
United States	$	37,121	$	22,699	$	7,022
Germany		4,314		3,402		1,393
Rest of Europe		19,142		14,097		3,516
All other countries		7,212		2,729		332
Product revenue	$	67,789	$	42,927	$	12,263

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Principles of Consolidation

Use of Estimates

Cash, Cash Equivalents and Restricted Cash

	December 31, 2020		December 31, 2019
	(in thousands)
Cash and cash equivalents	$	50,423	$	139,045
Restricted cash		1,450		1,450
Total cash, cash equivalents, and restricted cash	$	51,873	$	140,495

Short-Term Investments

Concentration of Credit Risk

Concentration of Customers

Fair Value of Financial Instruments

Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Accounts Receivable and Allowance for Doubtful Accounts

The following table summarizes the activity in the allowance for doubtful accounts:

	For the Year Ended December 31,
	2020			2019			2018
	(in thousands)
Beginning balance	$	194		$	76		$	—
Amounts charged to costs and expenses		205			121			77
Write-offs		(19	)		(3	)		(1	)
Ending balance	$	380		$	194		$	76

Inventory

Property and Equipment

Impairment of Long-Lived Assets

Revenue

Research and Development Costs

Research and development costs, including new product development, regulatory compliance, and clinical research are expensed as incurred.

Accrued Research and Development Costs

Stock-Based Compensation

Leases

Defined Contribution Plan

Comprehensive Loss

Comprehensive loss is comprised of net loss and changes in unrealized gains and losses on the Company’s available-for-sale investments.

Recently Adopted Accounting Pronouncements

Recent Accounting Pronouncements Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

	December 31, 2020		December 31, 2019
	(in thousands)
Cash and cash equivalents	$	50,423	$	139,045
Restricted cash		1,450		1,450
Total cash, cash equivalents, and restricted cash	$	51,873	$	140,495

Summary of Activity in Allowance for Doubtful Accounts

The following table summarizes the activity in the allowance for doubtful accounts:

	For the Year Ended December 31,
	2020			2019			2018
	(in thousands)
Beginning balance	$	194		$	76		$	—
Amounts charged to costs and expenses		205			121			77
Write-offs		(19	)		(3	)		(1	)
Ending balance	$	380		$	194		$	76

Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value

The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy:

	December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	126,363	$	—	$	—	$	126,363
Money market funds		35,053		—		—		35,053
Commercial paper		—		31,968		—		31,968
Total assets	$	161,416	$	31,968	$	—	$	193,384

	December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	43,245	$	—	$	—	$	43,245
Money market funds		29,386		—		—		29,386
Reverse repurchase agreements		—		10,000		—	$	10,000
Commercial paper		—		6,958		—	$	6,958
Corporate bonds		—		8,096		—	$	8,096
Total assets	$	72,631	$	25,054	$	—	$	97,685

Cash Equivalents and Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2020

Cash And Cash Equivalents [Abstract]

Summary of Cash Equivalents and Short-Term Investments

The following is a summary of the Company’s cash equivalents and short-term investments:

	December 31, 2020
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	126,354	$	11	$	(2	)	$	126,363
Money market funds		35,053		—		—			35,053
Commercial paper		31,968		—		—			31,968
Total	$	193,375	$	11	$	(2	)	$	193,384
Reported as:
Cash equivalents								$	41,453
Short-term investments									151,931
Total								$	193,384

	December 31, 2019
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	43,219	$	27	$	(1	)	$	43,245
Money market funds		29,386		—		—			29,386
Reverse repurchase agreements		10,000		—		—			10,000
Commercial paper		6,958		—		—			6,958
Corporate bonds		8,087		9		—			8,096
Total	$	97,650	$	36	$	(1	)	$	97,685
Reported as:
Cash equivalents								$	41,381
Short-term investments									56,304
Total								$	97,685

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Inventory

Inventory consists of the following:

	December 31,
	2020		2019
	(in thousands)
Raw material	$	4,995	$	2,501
Work in progress		6,051		1,364
Finished goods		16,952		6,642
Consigned inventory		1,861		1,567
Total inventory	$	29,859	$	12,074

Schedule of Property and Equipment

Property and equipment, net consists of the following:

	December 31,
	2020			2019
	(in thousands)
Equipment	$	3,794		$	3,759
Equipment on loan to customers		1,756			1,495
Office furniture		157			76
Software		175			97
Leasehold improvements		5,808			1,329
Construction in progress		7,800			553
Property and equipment, gross		19,490			7,309
Less accumulated depreciation and amortization		(3,128	)		(2,399	)
Total property and equipment, net	$	16,362		$	4,910

Schedule of Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2020		2019
	(in thousands)
Accrued employee compensation	$	10,885	$	8,139
Accrued research and development costs		3,057		3,090
Accrued asset purchases		2,527		—
Accrued professional services		1,325		804
Other		2,148		1,744
Total accrued liabilities	$	19,942	$	13,777

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Minimum Future Rental Payments

The following are minimum future rental payments owed under these agreements which have commenced as of December 31, 2020:

	(in thousands)
2021	$	1,946
2022		2,123
2023		1,529
2024		1,546
2025		1,594
Thereafter		3,232
Total minimum lease payments	$	11,970
Less: imputed interest		(3,609	)
Total lease liability	$	8,361

Schedule of Minimum Future Rental Payments Not Yet Commenced

The following are minimum future rental payments owed for the modified 5403 Betsy Ross Lease which has not yet commenced as of December 31, 2020:

	(in thousands)
2021	$	—
2022		345
2023		1,044
2024		1,078
2025		1,112
Thereafter		2,253
Total minimum lease payments	$	5,832

Term Notes (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Long Term Debt and Net Premium Balance

Long-term debt and net premium balances are as follows:

	December 31,
	2020			2019
	(in thousands)
Principal amount of term note	$	16,500		$	13,334
Net premium associated with accretion of final payment and other debt issuance costs		119			485
Term note, current and noncurrent		16,619			13,819
Less term note, current portion		(3,300	)		(6,667	)
Term note, noncurrent portion	$	13,319		$	7,152

Schedule of Future Minimum Payments for Principal and Interest

Future minimum payments of principal and estimated payments of interest on the Company’s outstanding variable rate borrowings as of December 31, 2020 are as follows:

Year ending December 31:	(in thousands)
2021	$	3,861
2022		6,961
2023		8,294
Total future payments		19,116
Less amounts representing interest		(1,048	)
Less final payment		(1,568	)
Total principal amount of term note payments	$	16,500

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Total Stock-Based Compensation

Total stock-based compensation was as follows:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
Cost of product revenue	$	496	$	268	$	67
Research and development		2,464		943		235
Sales and marketing		3,478		972		294
General and administrative		3,912		1,463		701
Total stock-based compensation	$	10,350	$	3,646	$	1,297

Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions

The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions:

	Year Ended December 31,
	2019	2018
Expected term (in years)	6.08	6.08
Expected volatility	42.4%-42.9%	40.8%-41.9%
Risk-free interest rate	2.4%-2.6%	2.5%-3.1%
Expected dividend yield	0%	0%

Schedule of Option Activity under 2009 Plan and 2019 Plan

Stock Options

Activity under the 2009 Plan and 2019 Plan is set forth below:

Schedule of RSU Activity under 2019 Plan

RSU activity under the 2019 Plan is set forth below:

	Number of Shares			Weighted- Average Grant Date Fair Value Per Share
Balance, December 31, 2018		—		$	—
RSUs granted		288,170			38.28
RSUs forfeited		(5,600	)		40.01
RSUs vested		(1,666	)		59.79
Balance, December 31, 2019		280,904		$	38.12
RSUs granted		687,223			51.34
RSUs forfeited		(38,650	)		41.55
RSUs vested		(69,900	)		38.46
Balance, December 31, 2020		859,577		$	48.50

Schedule of Fair Value of ESPP Shares Estimated Using Black-Scholes Option Pricing Model Assumptions

	Year Ended December 31,	Year Ended December 31,
	2020	2019
Expected term (in years)	0.5	0.5
Expected volatility	44.31%-74.03%	76.93%
Risk-free interest rate	0.12%-0.3%	1.89%
Expected dividend yield	0%	0%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Income (Loss) Before Income Taxes

The following table presents income (loss) before income taxes for the periods presented:

	December 31,
	2020			2019			2018
	(in thousands)
Domestic	$	(65,957	)	$	(51,179	)	$	(41,145	)
Foreign		338			132			81
Total loss before income taxes	$	(65,619	)	$	(51,047	)	$	(41,064	)

Schedule of Current Income Tax Provision

Current income tax provision consists of the following:

	December 31,
	2020		2019		2018
	(in thousands)
Domestic	$	3	$	—	$	3
Foreign		77		62		35
Total current income tax provision	$	80	$	62	$	38

Components of Deferred Tax Assets

The components of the deferred tax assets are as follows:

	December 31,
	2020			2019
	(in thousands)
Deferred tax assets:
Net operating loss carryovers	$	73,453		$	49,862
Fixed and intangible assets		718			450
Accruals and reserves		2,245			1,619
Stock-based compensation		2,060			780
Research and development credits		3,379			2,336
Contributions		42			20
Lease liability		2,004			2,135
Total deferred tax assets		83,901			57,202
Less valuation allowance		(82,087	)		(55,085	)
Gross deferred tax assets		1,814			2,117
Deferred tax liabilities:
Right-of-use-assets		(1,814	)		(2,117	)
Gross deferred tax liabilities		(1,814	)		(2,117	)
Total net deferred tax assets	$	—		$	—

Reconciliation of Statutory Federal Income Tax

Reconciliation of the statutory federal income tax to the Company’s effective tax is as follows:

	December 31,
	2020			2019			2018
	(in thousands)
Income tax benefit at federal statutory rate	$	(13,780	)	$	(10,720	)	$	(8,624	)
State and local income taxes net of federal tax benefit		(9	)		(9	)		3
Foreign tax rate differential		6			35			11
Change in valuation allowance		27,990			14,470			8,497
Stock-based compensation		(13,425	)		(3,403	)		123
R&D tax credits		(611	)		(354	)		(313	)
Other		(91	)		43			341
Total current income tax provision	$	80		$	62		$	38

Schedule of Unrecognized Tax Benefits

The activity related to the gross amount of unrecognized tax benefits is as follows:

	December 31,
	2020			2019		2018
	(in thousands)
Beginning balance	$	2,586		$	1,896	$	893
Additions (Reductions) based on tax positions related to prior years		(3	)		—		394
Additions based on tax positions related to current years		1,163			690		609
Balance at end of year	$	3,746		$	2,586	$	1,896

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share

	December 31,
	2020		2019		2018
	(in thousands)
Convertible preferred stock on an as-converted basis		—		—		18,670,328
Common stock options issued and outstanding		2,087,202		3,315,001		3,636,358
Restricted stock units		859,577		280,904		—
Employee stock purchase plan		15,251		16,420		—
Early exercised options subject to future vesting		—		—		13,422
Convertible preferred stock warrants		—		—		54,903
Common stock warrants		—		—		176,218
Total		2,962,030		3,612,325		22,551,229

Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Disaggregation Of Revenue [Abstract]

Schedule of Product Revenue Based on Product Line and Location

Disaggregation of revenue

The following table represents the Company’s product revenue based on product line:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
Peripheral	$	41,994	$	26,325	$	8,828
Coronary		24,586		15,621		3,210
Other		1,209		981		225
Product revenue	$	67,789	$	42,927	$	12,263

The following table represents the Company’s product revenue based on the location to which the product is shipped:

	Year Ended December 31,
	2020		2019		2018
	(in thousands)
United States	$	37,121	$	22,699	$	7,022
Germany		4,314		3,402		1,393
Rest of Europe		19,142		14,097		3,516
All other countries		7,212		2,729		332
Product revenue	$	67,789	$	42,927	$	12,263

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Jun. 19, 2020 USD ($) $ / shares shares	Nov. 15, 2019 USD ($) $ / shares shares	Mar. 11, 2019 USD ($) $ / shares shares	Apr. 30, 2019 shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Mar. 05, 2019 shares
Organization and Basis of Presentation [Line Items]
Entity incorporation, date of incorporation					Jun. 17, 2009
Common stock, conversion basis					one-to-one basis
Proceeds from issuance of common stock in public offering, net of issuance costs paid \| $					$ 83,368	$ 96,856
Cash, cash equivalents and short-term investments \| $					$ 202,400
Common Stock
Organization and Basis of Presentation [Line Items]
Proceeds from initial public offering \| $			$ 99,900
Issuance of common stock upon net exercise of warrants, shares			101,744	29,887		180,952
Net proceeds from issuance on follow-on offering \| $	$ 83,400	$ 96,700
Warrants
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion			54,903
Initial Public Offering
Organization and Basis of Presentation [Line Items]
Common stock issued			6,555,000
Common stock, offering price per share \| $ / shares			$ 17.00
Stock split, conversion ratio			1
Initial Public Offering \| Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued						6,555,000
Convertible preferred stock, shares issued upon conversion							18,670,259
Over-Allotment Option
Organization and Basis of Presentation [Line Items]
Common stock issued			855,000
Over-Allotment Option \| Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued					1,955,000	2,854,048
Private Placement
Organization and Basis of Presentation [Line Items]
Common stock issued			588,235
Proceeds from issuance of common stock in public offering, net of issuance costs paid \| $			$ 10,000
Underwritten Public Offering \| Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued	1,955,000	2,854,048
Common stock, offering price per share \| $ / shares	$ 45.75	$ 36.25
Shares sold to underwriters option to purchase additional shares	255,000	372,267

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 50,423	$ 139,045
Restricted cash	1,450	1,450
Total cash, cash equivalents, and restricted cash	$ 51,873	$ 140,495	$ 40,093	$ 51,923

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Customer Segment	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($)	Mar. 31, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Notice period for cancellation of agreement	30 days
Defined contribution plan, maximum amount of matching contributions amount	$ 3,000
Defined contribution plan, contribution amount	1,100,000	$ 0	$ 0
Foreign currency transaction realized and unrealized gain (loss)	$ 261,000	$ 56,000	$ (46,000)
Number of Operating Segments \| Segment	1
Reserve for credit losses				$ 200,000
ASU 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle accounting standards update immaterial effect [true false]	true
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	5 years
Percentage of income tax position required to recognize uncertain income tax position	50.00%
Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Number of customers \| Customer	1	1
Customer \| Revenue Benchmark \| Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Credit Concentration Risk \| Accounts Receivable \| Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	15.00%	11.00%

Summary of Significant Accounting Policies - Summary of Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 194	$ 76
Amounts charged to costs and expenses	205	121	$ 77
Write-offs	(19)	(3)	(1)
Ending balance	$ 380	$ 194	$ 76

Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Total assets	$ 193,384	$ 97,685
Level 1
Assets:
Total assets	161,416	72,631
Level 2
Assets:
Total assets	31,968	25,054
U.S. Treasury securities
Assets:
Total assets	126,363	43,245
U.S. Treasury securities \| Level 1
Assets:
Total assets	126,363	43,245
Money Market Funds
Assets:
Total assets	35,053	29,386
Money Market Funds \| Level 1
Assets:
Total assets	35,053	29,386
Reverse Repurchase Agreements
Assets:
Total assets		10,000
Reverse Repurchase Agreements \| Level 2
Assets:
Total assets		10,000
Commercial Paper
Assets:
Total assets	31,968	6,958
Commercial Paper \| Level 2
Assets:
Total assets	$ 31,968	6,958
Corporate Bonds
Assets:
Total assets		8,096
Corporate Bonds \| Level 2
Assets:
Total assets		$ 8,096

Cash Equivalents and Short-Term Investments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($)
Cash And Cash Equivalents [Line Items]
Realized gains on cash equivalents and short-term investments	$ 21,000
Maximum
Cash And Cash Equivalents [Line Items]
Available for sale securities remaining contractual maturities	1 year

Cash Equivalents and Short-Term Investments - Summary of Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Cash equivalents, Fair Value	$ 41,453	$ 41,381
Cash equivalents and short-term investments, Amortized Cost Basis	193,375	97,650
Cash equivalents and short-term investments, Unrealized Gains	11	36
Cash equivalents and short-term investments, Unrealized losses	(2)	(1)
Cash equivalents and short-term investments, Fair Value	193,384	97,685
Short-term investments	151,931	56,304
U.S. Treasury securities
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	126,354	43,219
Short-term investments Unrealized Gains	11	27
Short-term investments Unrealized Losses	(2)	(1)
Short-term investments, Fair Value	126,363	43,245
Commercial Paper
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	31,968	6,958
Short-term investments, Fair Value	31,968	6,958
Reverse Repurchase Agreements
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis		10,000
Short-term investments, Fair Value		10,000
Corporate Bonds
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis		8,087
Short-term investments Unrealized Gains		9
Short-term investments, Fair Value		8,096
Money Market Funds
Cash And Cash Equivalents [Line Items]
Cash equivalents Amortized Cost Basis	35,053	29,386
Cash equivalents, Fair Value	$ 35,053	$ 29,386

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw material	$ 4,995	$ 2,501
Work in progress	6,051	1,364
Finished goods	16,952	6,642
Consigned inventory	1,861	1,567
Total inventory	$ 29,859	$ 12,074

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 19,490	$ 7,309
Less accumulated depreciation and amortization	(3,128)	(2,399)
Total property and equipment, net	16,362	4,910
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,794	3,759
Equipment Loan To Customer
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,756	1,495
Office Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	157	76
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	175	97
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,808	1,329
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,800	$ 553

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 1,863	$ 1,337	$ 700

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued employee compensation	$ 10,885	$ 8,139
Accrued research and development costs	3,057	3,090
Accrued asset purchases	2,527
Accrued professional services	1,325	804
Other	2,148	1,744
Total accrued liabilities	$ 19,942	$ 13,777

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2019 USD ($) ft²	May 31, 2018 ft²	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) ft²	Dec. 31, 2018 USD ($)	Sep. 01, 2022 USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset	$ 8,825		$ 7,568	$ 8,825
Operating lease liabilities			8,361
Operating lease cost			2,200	$ 1,200
Rent expense					$ 900
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset			200
Operating lease liabilities			$ 200
Operating lease, weighted average remaining lease term			2 years 4 months
Operating lease liability, weighted average incremental borrowing rate			6.98%
5403 Lease \| Santa Clara, California
Loss Contingencies [Line Items]
Area of office and laboratory space \| ft²		35,000
Lease term expiration date		Aug. 31, 2022
Lease commencement date		2018-09
Letter of credit secured by restricted cash			$ 500
Operating lease right-of-use asset			1,300
Operating lease liabilities			$ 1,400
Operating lease, remaining lease term			1 year 8 months
5353 Lease \| Santa Clara, California
Loss Contingencies [Line Items]
Area of office and laboratory space \| ft²	50,200			50,200
Lease term expiration date	Aug. 31, 2022
Lease commencement date				2019-12
Operating lease right-of-use asset			$ 6,100
Operating lease liabilities			$ 6,800
Operating lease, remaining lease term				6 years 11 months
Initial term of first building	96 months			96 months
Lessee, Operating Lease, Existence of Option to Extend				true
Lease rent abatement term for first building				19 months
Lease rent abatement term for second floor				4 months
5353 Lease \| Santa Clara, California \| Initial Security Deposit
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash	$ 1,000			$ 1,000
5353 Lease \| Santa Clara, California \| Scenario Forecast
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash						$ 1,500
5403 and 5353 Lease \| Santa Clara, California
Loss Contingencies [Line Items]
Option to extend term on one or both buildings	5 years			5 years
5403 and 5353 Lease \| Santa Clara, California \| Maximum
Loss Contingencies [Line Items]
Tenant improvements allowance	$ 1,800			$ 1,800

Commitments and Contingencies - Schedule of Minimum Future Rental Payments (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021	$ 1,946
2022	2,123
2023	1,529
2024	1,546
2025	1,594
Thereafter	3,232
Total minimum lease payments	11,970
Less: imputed interest	(3,609)
Total lease liability	$ 8,361

Commitments and Contingencies - Schedule of Minimum Future Rental Payments Not Yet Commenced (Details) - 5403 Betsy Ross Lease $ in Thousands	Dec. 31, 2020 USD ($)
Lessee, Operating Lease, Not yet Commenced, Description [Abstract]
2022	$ 345
2023	1,044
2024	1,078
2025	1,112
Thereafter	2,253
Total minimum lease payments	$ 5,832

Term Notes - Additional Information (Details) - USD ($)		12 Months Ended
Term Notes - Additional Information (Details) - USD ($)	Feb. 29, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Feb. 28, 2018
Debt Instrument [Line Items]
Debt Amount		$ 16,500,000	$ 13,334,000
Debt, final payment amount		1,568,000
Interest expense		$ 1,212,000	944,000	$ 401,000
Loan and Security Agreement
Debt Instrument [Line Items]
Debt, final payment as percentage of original aggregate principal amount		6.75%
Debt, final payment amount		$ 1,000,000				$ 1,000,000
Debt, warrants issued		34,440
Debt, fair value of warrants issued		$ 100,000
Proceeds of supplemental term loan	$ 4,300,000
Debt payments description		The Amended Credit Facility provides an interest-only payment period which will end on (a) June 30, 2021, if the Company’s revenue for the trailing 12-month period ended June 30, 2021 is not at least 75% of the Company’s projections; (b) December 31, 2021, if the Company achieves the financial performance target referred to in clause (a), but does not obtain premarket approval of the Company’s C2 catheters from the FDA by such date and/or the Company’s trailing 12-month revenue for the period ending December 31, 2021 is not at least 75% of the Company’s projections; or (c) June 30, 2022, if the Company achieves the milestones referred to in clauses (a) and (b).
Interest expense		$ 600,000	500,000	200,000
Amortization of debt discount		$ 600,000	$ 400,000	200,000
Loan and Security Agreement \| Interest Payment End On June 30, 2021
Debt Instrument [Line Items]
Debt instrument percentage of projected revenue to be achieved	75.00%
Loan and Security Agreement \| Interest Payment End On December 31, 2021
Debt Instrument [Line Items]
Debt instrument percentage of projected financial performance target	75.00%
Loan and Security Agreement \| Supplemental Term Loan
Debt Instrument [Line Items]
Debt Amount	$ 16,500,000
Debt interest rate		3.50%
Debt, final payment amount		$ 1,600,000
Proceeds of supplemental term loan, net of final balloon payment fee	$ 3,300,000
Debt maturity date	Dec. 01, 2023
Loan and Security Agreement \| Minimum
Debt Instrument [Line Items]
Debt interest rate		1.75%
Loan and Security Agreement \| Minimum \| Prime Rate \| Supplemental Term Loan
Debt Instrument [Line Items]
Debt interest rate basis	1.25%
Loan and Security Agreement \| Maximum
Debt Instrument [Line Items]
Debt interest rate basis		2.75%
Loan and Security Agreement \| Maximum \| Supplemental Term Loan
Debt Instrument [Line Items]
Debt interest rate	3.50%
Loan and Security Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Termination of Line of Credit Facility	$ 2,000,000
Loan and Security Agreement \| Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Line of credit facility termination fee	$ 100,000
Loan and Security Agreement \| Silicon Valley Bank \| Short Term Notes
Debt Instrument [Line Items]
Debt Amount						15,000,000
Loan and Security Agreement \| Silicon Valley Bank \| Short Term Notes \| Tranche One
Debt Instrument [Line Items]
Debt Amount					$ 10,000,000
Loan and Security Agreement \| Silicon Valley Bank \| Short Term Notes \| Tranche Two
Debt Instrument [Line Items]
Debt Amount				$ 5,000,000
Loan and Security Agreement \| Silicon Valley Bank \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt Amount						$ 2,000,000

Term Notes - Schedule of Long Term Debt and Net Premium Balance (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument Periodic Payment [Abstract]
Principal amount of term note	$ 16,500	$ 13,334
Net premium associated with accretion of final payment and other debt issuance costs	119	485
Term note, current and noncurrent	16,619	13,819
Less term note, current portion	(3,300)	(6,667)
Term note, noncurrent portion	$ 13,319	$ 7,152

Term Notes - Schedule of Future Minimum and Estimated Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2021	$ 3,861
2022	6,961
2023	8,294
Total future payments	19,116
Less amounts representing interest	(1,048)
Less final payment	(1,568)
Total principal amount of term note payments	$ 16,500	$ 13,334

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	12 Months Ended
	Mar. 11, 2019	Mar. 06, 2019	Mar. 05, 2019	Apr. 30, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2017
Temporary Equity And Stockholders Equity [Line Items]
Preferred stock, shares authorized					5,000,000	5,000,000
Preferred stock, shares issued					0	0
Preferred stock, shares outstanding					0	0
Preferred Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Debt, warrants issued					0	0
Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Debt, warrants issued					0	0
Initial Public Offering \| Common Stock Warrants Related to Convertible Preferred Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrant issued		54,903
Adjustments to additional paid in capital		$ 0.8
Issuance of common stock upon net exercise of warrants, Shares				49,321
Initial Public Offering \| Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants exercised		91,446
Warrants exercised price		$ 17.00
Common stock issued upon exercise of common stock warrants		79,632
Convertible Preferred Stock
Temporary Equity And Stockholders Equity [Line Items]
Convertible preferred stock, shares outstanding			18,670,259				18,670,328	17,510,045
Common Stock
Temporary Equity And Stockholders Equity [Line Items]
Conversion of stock, common stock issued			18,670,259
Issuance of common stock upon net exercise of warrants, Shares	101,744			29,887	180,952

Stock-Based Compensation - Schedule of Total Stock-Based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 10,350	$ 3,646	$ 1,297
Cost of Product Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	496	268	67
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	2,464	943	235
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	3,478	972	294
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,912	$ 1,463	$ 701

Stock-Based Compensation - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jun. 17, 2009	Feb. 28, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 06, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses capitalized amount			$ 316,000	$ 0	$ 0
Expected dividend yield			0.00%	0.00%	0.00%
Options granted			0	442,858	1,015,963
Weighted-average grant date fair value of options granted				$ 6.58	$ 2.56
Grant date fair value of options vested			$ 2,300,000	$ 1,900,000	$ 1,600,000
Unvested stock options			$ 2,500,000
Unvested stock options, remaining weighted-average period			1 year 3 months 18 days
Stock-based compensation			$ 10,350,000	3,646,000	$ 1,297,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
Cliff vesting, percentage			25.00%
Share-based compensation vesting rights, terms			The RSUs generally vest over a four-year period with a 25% one-year cliff or over a three-year period in equal amounts on a semi-annual basis,
Unvested stock options, remaining weighted-average period			3 years 1 month 6 days
Grant date fair value of RSU vested			$ 2,700,000	$ 100,000
Number of Shares, RSUs granted			687,223	288,170	0
Unrecognized stock-based compensation			$ 35,300,000
2019 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		2,000,430	2,689,624
Maximum period of automatic annual increase in common stock reserved for issuance		10 years
Automatic annual increase in common stock reserved for issuance		3.00%
Start date for automatic annual increase for common stock reserved for issuance under plan		Jan. 01, 2020
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock owned by individual	10.00%
Vesting period			4 years
Cliff vesting, percentage			25.00%
Share-based compensation vesting rights, terms			If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the Board. Options granted under the Plan have a term of up to 10 years and generally vest over a 4 year period with a straight-line vesting and a 25% one year cliff.
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of stock as percentage of fair value	110.00%
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted term			10 years
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield			0.00%	0.00%
Common stock reserved for issuance						300,650
Maximum period of automatic annual increase in common stock reserved for issuance			10 years
Automatic annual increase in common stock reserved for issuance			1.00%
Start date for automatic annual increase for common stock reserved for issuance under plan			Jan. 01, 2020
Purchase shares of common stock, price per share, percentage of fair market value			85.00%
Stock-based compensation			$ 786,000	$ 255,000

Stock-Based Compensation - Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)		6 years 29 days	6 years 29 days
Expected volatility, minimum		42.40%	40.80%
Expected volatility, maximum		42.90%	41.90%
Risk-free interest rate, minimum		2.40%	2.50%
Risk-free interest rate, maximum		2.60%	3.10%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Schedule of Option Activity under 2009 Plan and 2019 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares Available for Grant
Shares Available for Grant, Beginning balance	1,704,244	392,299	426,370
Shares Available for Grant, Awards authorized	943,345	2,000,430	691,503
Shares Available for Grant, Options expired		(287,600)
Shares Available for Grant, Options granted		(442,858)	(1,015,963)
Shares Available for Grant, Options cancelled	42,035	41,973	290,389
Shares Available for Grant, Ending balance	2,689,624	1,704,244	392,299	426,370
Number of Shares
Number of Shares, Beginning balance	3,315,001	3,636,358	3,108,604
Number of Shares, Options granted	0	442,858	1,015,963
Number of Shares, Options exercised	(1,185,764)	(722,242)	(197,820)
Number of Shares, Options cancelled	(42,035)	(41,973)	(290,389)
Number of Shares, Ending balance	2,087,202	3,315,001	3,636,358	3,108,604
Number of Shares, Vested and exercisable	1,360,650
Number of Shares, Vested and expected to vest	2,087,202
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 5.08	$ 3.54	$ 2.81
Weighted-Average Exercise Price Per Share, Options granted		14.69	5.25
Weighted-Average Exercise Price Per Share, Options exercised	3.64	3.10	2.20
Weighted-Average Exercise Price Per Share, Options cancelled	4.45	3.85	3.42
Weighted-Average Exercise Price Per Share, Ending balance	5.92	$ 5.08	$ 3.54	$ 2.81
Weighted-Average Exercise Price Per Share, Vested and exercisable	4.63
Weighted-Average Exercise Price Per Share, Vested and expected to vest	$ 5.92
Weighted-Average Remaining Term
Weighted-Average Remaining Term (in years), Balance	6 years 9 months 7 days	7 years 3 months 10 days	7 years 9 months 14 days	8 years 10 days
Weighted-Average Remaining Term, Vested and exercisable	6 years 4 months 9 days
Weighted-Average Remaining Term, Vested and expected to vest	6 years 9 months 7 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Balance	$ 204,137	$ 128,744	$ 11,267	$ 3,647
Aggregate Intrinsic Value, Vested and exercisable	134,825
Aggregate Intrinsic Value, Vested and expected to vest	$ 204,137

Stock-Based Compensation - Schedule of RSU Activity under 2019 Plan (Detail) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Number of Shares, Beginning balance	280,904
Number of Shares, RSUs granted	687,223	288,170	0
Number of Shares, RSUs forfeited	(38,650)	(5,600)
Number of Shares, RSUs vested	(69,900)	(1,666)
Number of Shares, Ending balance	859,577	280,904
Weighted-Average Grant Date Fair Value Per Share
Weighted-Average Grant Date Fair Value Per Share, Beginning balance	$ 38.12
Weighted-Average Grant Date Fair Value Per Share, RSUs granted	51.34	$ 38.28
Weighted-Average Grant Date Fair Value Per Share, RSUs forfeited	41.55	40.01
Weighted-Average Grant Date Fair Value Per Share, RSUs vested	38.46	59.79
Weighted-Average Grant Date Fair Value Per Share, Ending balance	$ 48.50	$ 38.12

Stock-Based Compensation - Schedule of Fair Value of ESPP Shares Estimated Using Black-Scholes Option Pricing Model Assumptions (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 years 29 days	6 years 29 days
Expected volatility, minimum		42.40%	40.80%
Expected volatility, maximum		42.90%	41.90%
Risk-free interest rate, minimum		2.40%	2.50%
Risk-free interest rate, maximum		2.60%	3.10%
Expected dividend yield	0.00%	0.00%	0.00%
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months
Expected volatility, minimum	44.31%
Expected volatility		76.93%
Expected volatility, maximum	74.03%
Risk-free interest rate, minimum	0.12%
Risk-free interest rate		1.89%
Risk-free interest rate, maximum	0.30%
Expected dividend yield	0.00%	0.00%

Income Taxes -Schedule of Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic	$ (65,957)	$ (51,179)	$ (41,145)
Foreign	338	132	81
Total loss before income taxes	$ (65,619)	$ (51,047)	$ (41,064)

Income Taxes - Schedule of Current Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 80	$ 62	$ 38
Domestic Federal
Income Taxes Disclosure [Line Items]
Total current income tax provision	3		3
Foreign Tax Authority
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 77	$ 62	$ 35

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Net operating loss carryovers	$ 73,453	$ 49,862
Fixed and intangible assets	718	450
Accruals and reserves	2,245	1,619
Stock-based compensation	2,060	780
Research and development credits	3,379	2,336
Contributions	42	20
Lease liability	2,004	2,135
Total deferred tax assets	83,901	57,202
Less valuation allowance	(82,087)	(55,085)
Gross deferred tax assets	1,814	2,117
Deferred tax liabilities:
Right-of-use-assets	(1,814)	(2,117)
Gross deferred tax liabilities	$ (1,814)	$ (2,117)

Income Taxes - Reconciliation of Statutory Federal Income Tax (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation
Income tax benefit at federal statutory rate	$ (13,780)	$ (10,720)	$ (8,624)
State and local income taxes net of federal tax benefit	(9)	(9)	3
Foreign tax rate differential	6	35	11
Change in valuation allowance	27,990	14,470	8,497
Stock-based compensation	(13,425)	(3,403)	123
R&D tax credits	(611)	(354)	(313)
Other	(91)	43	341
Total current income tax provision	$ 80	$ 62	$ 38

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes Disclosure [Line Items]
Increase in valuation allowance	$ 27.0	$ 22.8	$ 10.0
Domestic Federal
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 301.9
Net operating loss carryforwards	2030
Net operating loss carryforwards subject to expiration in 2031		80.8
Net operating loss carryforwards never expire		$ 221.1
Research and development credit carryforwards, california	$ 4.0
California \| State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 52.4
Net operating loss carryforwards	2031
Research and development credit carryforwards, california	$ 3.5
All Other States \| State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 123.7
Net operating loss carryforwards	2029

Income Taxes - Schedule of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unrecognized tax benefits [Abstract]
Beginning balance	$ 2,586	$ 1,896	$ 893
Reductions based on tax positions related to prior years	(3)
Additions based on tax positions related to prior years			394
Additions based on tax positions related to current years	1,163	690	609
Balance at end of year	$ 3,746	$ 2,586	$ 1,896

Net Loss Per Share - Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,962,030	3,612,325	22,551,229
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			18,670,328
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,087,202	3,315,001	3,636,358
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	859,577	280,904
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	15,251	16,420
Early Exercised Options Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			13,422
Convertible Preferred Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			54,903
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			176,218

Revenue - Schedule of Product Revenue Based on Product Line and Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Product revenue	$ 67,789	$ 42,927	$ 12,263
United States
Disaggregation Of Revenue [Line Items]
Product revenue	37,121	22,699	7,022
Germany
Disaggregation Of Revenue [Line Items]
Product revenue	4,314	3,402	1,393
Rest of Europe
Disaggregation Of Revenue [Line Items]
Product revenue	19,142	14,097	3,516
All Other Countries
Disaggregation Of Revenue [Line Items]
Product revenue	7,212	2,729	332
Peripheral
Disaggregation Of Revenue [Line Items]
Product revenue	41,994	26,325	8,828
Coronary
Disaggregation Of Revenue [Line Items]
Product revenue	24,586	15,621	3,210
Other
Disaggregation Of Revenue [Line Items]
Product revenue	$ 1,209	$ 981	$ 225

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details