0001564590-22-007162 | 10-K | XBRL Viewer

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Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 89,209	$ 50,423
Short-term investments	111,772	151,931
Accounts receivable, net	37,435	11,689
Inventory	42,978	29,859
Prepaid expenses and other current assets	4,508	2,398
Total current assets	285,902	246,300
Operating lease right-of-use assets	27,496	7,568
Property and equipment, net	24,361	16,362
Equity method investment	5,987
Other assets	1,936	1,812
TOTAL ASSETS	345,682	272,042
CURRENT LIABILITIES:
Accounts payable	3,520	1,466
Term notes, current portion	5,500	3,300
Accrued liabilities	40,870	19,942
Lease liability, current portion	1,738	873
Total current liabilities	51,628	25,581
Lease liability, noncurrent portion	28,321	7,488
Term notes, noncurrent portion	11,630	13,319
Related party contract liability, noncurrent portion	12,273
TOTAL LIABILITIES	103,852	46,388
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, 2021 and 2020
Common stock, $0.001 par value; 281,274,838 shares authorized; 35,444,472 and 34,684,337 issued and outstanding as of December 31, 2021 and 2020	35	35
Additional paid-in capital	494,806	469,283
Accumulated other comprehensive income (loss)	(202)	9
Accumulated deficit	(252,809)	(243,673)
TOTAL STOCKHOLDERS’ EQUITY	241,830	225,654
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 345,682	$ 272,042

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
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	35,444,472	34,684,337
Common stock, shares outstanding	35,444,472	34,684,337

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Product revenue	$ 237,146,000	$ 67,789,000	$ 42,927,000
Cost of revenue:
Cost of product revenue	41,438,000	20,991,000	17,159,000
Gross profit	195,708,000	46,798,000	25,768,000
Operating expenses:
Research and development	50,544,000	36,926,000	32,853,000
Sales and marketing	111,288,000	51,672,000	30,620,000
General and administrative	34,747,000	23,863,000	14,134,000
Total operating expenses	196,579,000	112,461,000	77,607,000
Loss from operations	(871,000)	(65,663,000)	(51,839,000)
Interest expense	(1,096,000)	(1,212,000)	(944,000)
Change in fair value of warrant liability			(609,000)
Share in net loss of equity method investment	(6,286,000)
Other income (expense), net	(582,000)	1,256,000	2,345,000
Net loss before taxes	(8,835,000)	(65,619,000)	(51,047,000)
Income tax provision	301,000	80,000	62,000
Net loss	(9,136,000)	(65,699,000)	(51,109,000)
Unrealized gain (loss) on available-for-sale securities	(211,000)	(5,000)	35,000
Adjustment for net gain realized and included in other income, net		(21,000)
Total comprehensive loss	$ (9,347,000)	$ (65,725,000)	$ (51,074,000)
Net loss per share, basic and diluted	$ (0.26)	$ (1.99)	$ (2.14)
Shares used in computing net loss per share, basic and diluted	35,098,130	33,088,095	23,904,828

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, 2018	$ (122,588,000)				$ 2,000			$ 4,275,000				$ (126,865,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2018				18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018				$ 152,806,000
Beginning 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 shares to common stock upon initial public offering, Shares				(18,670,328)
Temporary equity conversion of preferred stock value to common stock upon initial public offering				$ (152,806,000)
Conversion of preferred 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 in connection with initial/public offering		$ 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
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)
Unrealized gain (loss) on available-for-sale securities	35,000										$ 35,000
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 in connection with initial/public offering			$ 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
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
Unrealized gain (loss) on available-for-sale securities	(5,000)										(5,000)
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
Exercise of stock options	$ 3,049,000							3,049,000
Exercise of stock options, Shares	547,155				547,155
Issuance of common stock under employee stock purchase plan	$ 2,837,000				$ 36,833,000			2,837,000
Issuance of common stock in connection with vesting of restricted stock units					239,213,000
Restricted stock units withheld in net settlement for tax	(8,337,000)				(63,066,000)			(8,337,000)
Stock-based compensation	27,974,000							27,974,000
Unrealized gain (loss) on available-for-sale securities	(211,000)										(211,000)
Net loss	(9,136,000)											(9,136,000)
Ending balance at Dec. 31, 2021	$ 241,830,000				$ 35,000			$ 494,806,000			$ (202,000)	$ (252,809,000)
Ending balance, Shares at Dec. 31, 2021					35,444,472

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Initial Public Offering
Issuance costs		$ 11.5
Public Offering
Issuance costs	$ 6.1	$ 6.8

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (9,136)	$ (65,699)	$ (51,109)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,579	1,863	1,337
Share in net loss of equity method investment	6,286
Stock-based compensation	27,257	10,350	3,646
Amortization of right-of-use assets	1,957	1,483	944
Accretion of discount on available-for-sale securities	1,093	300	(543)
Loss on write down of fixed assets	7	187	67
Change in fair value of warrant liability			609
Amortization of debt issuance costs	511	646	436
Changes in operating assets and liabilities:
Accounts receivable	(25,746)	(4,312)	(4,527)
Inventory	(12,073)	(17,056)	(6,824)
Prepaid expenses and other current assets	(2,110)	(501)	(785)
Other assets	91	(306)	41
Accounts payable	1,870	(1,392)	1,272
Accrued and other current liabilities	21,637	4,017	8,339
Lease liabilities	(187)	(764)	(1,010)
Net cash provided by (used in) operating activities	15,036	(71,184)	(48,107)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(117,245)	(167,953)	(119,476)
Proceeds from maturities of available-for-sale securities	156,100	72,000	63,750
Purchase of property and equipment	(12,439)	(11,520)	(3,817)
Net cash provided by (used in) investing activities	26,416	(107,473)	(59,543)
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 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	(8,337)	(1,420)
Proceeds from term loans		3,265
Payment of deferred offering costs		(179)
Proceeds from stock option exercises	3,049	4,317	2,206
Proceeds from issuance of common stock under employee stock purchase plan	2,837	1,795
Proceeds from warrant exercises			110
Principal payment of term loan		(1,111)	(1,667)
Net cash provided by (used in) financing activities	(2,451)	90,035	208,052
Net increase (decrease) in cash, cash equivalents and restricted cash	39,001	(88,622)	100,402
Cash, cash equivalents and restricted cash at beginning of period	51,873	140,495	40,093
Cash, cash equivalents and restricted cash equivalents at end of period	90,874	51,873	140,495
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	586	549	534
Income tax paid	143	22	120
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued on conversion of convertible preferred stock			152,806
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	21,885	226	6,948
Property and equipment purchases included in accounts payable and accrued liabilities	1,923	2,448	52
Equity method investment obtained in exchange for related party contract liability	12,273
Transfer of fixed assets to inventory	$ 329	$ 413	$ 119

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2021

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, Japan and France.

As of December 31, 2021, the Company had cash, cash equivalents and short-term investments of $201.0 million, which are available to fund future operations. The Company believes that its cash, cash equivalents, and short-term investments as of December 31, 2021, 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.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

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 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,
	2021		2020
	(in thousands)
Cash and cash equivalents	$	89,209	$	50,423
Restricted cash		1,665		1,450
Total cash, cash equivalents, and restricted cash	$	90,874	$	51,873

Restricted cash as of December 31, 2021 and 2020 relates to letters of credit established for real property leases 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.

Equity Method Investments

Entities which the Company has significant influence over activities of the entity, but do not control, are accounted for under the equity method of accounting in accordance with Topic 323, Investments - Equity Method and Joint Ventures. The Company’s carrying value in the equity method investment is reported as equity method investment on the Company’s consolidated balance sheets. The Company records its proportionate share of the underlying income or loss which is recognized in share in net loss of equity method investment. For the year ended December 31, 2021, the Company’s share in the losses incurred by the equity method investee was $6.3 million. The Company eliminates any intra-entity profits to the extent of the Company’s beneficial interest.

The Company assesses its equity method investment for impairment when events or circumstances suggest that the carrying amount of the investment may be impaired. The Company considers all available evidence in assessing whether a decline in fair value is other than temporary. If the decline in fair value is determined to be other than temporary, the difference between the carrying amount of the investment and estimated fair value is recognized as an impairment charge.

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 purchasing investments with investment grade ratings. 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, 2021, 2020 and 2019 no customer accounted for 10% or more of the Company’s revenue. There were no customers which accounted for 10% or more of the Company’s accounts receivable as of December 31, 2021. One customer accounted for 15% of the Company’s accounts receivable as of December 31, 2020.

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 the Company’s 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 the Company’s assessment of expected credit losses for its 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,
	2021			2020			2019
	(in thousands)
Beginning balance	$	380		$	194		$	76
Amounts charged (reversed) to costs and expenses		(12	)		205			121
Write-offs		(18	)		(19	)		(3	)
Ending balance	$	350		$	380		$	194

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

To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, Revenue from Contracts with Customers, 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.

Product 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 portion of the Company’s revenue is generated through a consignment model under which inventory is maintained at hospitals.

Product 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.

For products sold through direct sales representatives, control is transferred upon delivery to customers. For products sold to distributors internationally and products sold to customers that utilize stocking orders, 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 IVL 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.

License Revenue

For arrangements that contain a license of the Company’s functional intellectual property with a customer, the Company considers whether the license grant is distinct from other performance obligations in the arrangement. A license grant of functional intellectual property is generally considered to be capable of being distinct if a customer can benefit from the license on its own or together with other readily available resources. License revenue for licenses of functional intellectual property is recognized at a point in time when the Company satisfies its performance obligation of transferring the license to the customer.

Consideration received in advance of the satisfaction of a performance obligation is recognized as a contract liability. No license revenues have been recognized for the year ended December 31, 2021.

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

For its operating leases with a lease term of 12 months or greater, 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.

Operating lease cost 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 of 1986, as amended. This plan allows eligible employees to defer a portion of their annual compensation on a pre-tax basis. The Company recognized expense related to its contributions to the plan of $2.5 million and $1.1 million for the years ended December 31, 2021 and 2020, respectively. The Company did not make such contributions for the year ended December 31, 2019.

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 losses of $0.8 million for the year ended December 31, 2021. There were

net foreign currency transaction gains of $0.3 million and $0.1 million for the years ended December 31, 2020 and 2019, respectively.

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. 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.

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,
	2021		2020		2019
Common stock options issued and outstanding		1,524,985		2,087,202		3,315,001
Restricted stock units		1,156,683		859,577		280,904
Employee stock purchase plan		10,028		15,251		16,420
Total		2,691,696		2,962,030		3,612,325

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 held predominantly in the United States with the exception of certain equipment on loan to customers held internationally, which was not material for the periods presented.

Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2021

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, 2021
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	80,155	$	—	$	—	$	80,155
Money market funds		47,541		—		—		47,541
Commercial paper		—		20,472		—		20,472
Corporate bonds		—		11,145		—		11,145
Total assets	$	127,696	$	31,617	$	—	$	159,313

	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

- 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, 2021

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, 2021
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	80,353	$	—	$	(198	)	$	80,155
Money market funds		47,541		—		—			47,541
Commercial paper		20,472		—		—			20,472
Corporate bonds		11,149		—		(4	)		11,145
Total	$	159,515	$	—	$	(202	)	$	159,313
Reported as:
Cash equivalents								$	47,541
Short-term investments									111,772
Total								$	159,313

	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

As of December 31, 2021, the fair value of the Company’s available-for-sale securities, by remaining contractual maturities, were as follows (in thousands):

One year or less	$	113,330
Greater than one year and less than two years		45,983
Total	$	159,313

For the years ended December 31, 2021 and 2019, the Company recognized no material realized gains or losses on cash equivalents and short-term investments. For the year ended December 31, 2020, the Company recognized $21,000 in realized gains on cash equivalents and short-term investments.

Balance Sheet Components

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

5. Balance Sheet Components

Inventory

Inventory consists of the following:

	December 31,
	2021		2020
	(in thousands)
Raw material	$	7,685	$	4,995
Work in progress		13,315		6,051
Finished goods		20,326		16,952
Consigned inventory		1,652		1,861
Total inventory	$	42,978	$	29,859

Property and Equipment, Net

Property and equipment, net consists of the following:

	December 31,
	2021			2020
	(in thousands)
Equipment	$	6,234		$	3,794
Equipment on loan to customers		1,714			1,756
Office furniture		549			157
Software		742			175
Leasehold improvements		17,742			5,808
Construction in progress		3,544			7,800
Property and equipment, gross		30,525			19,490
Less: accumulated depreciation and amortization		(6,164	)		(3,128	)
Total property and equipment, net	$	24,361		$	16,362

Depreciation and amortization expense amounted to $3.6 million, $1.9 million and $1.3 million for the years ended December 31, 2021, 2020 and 2019, respectively.

Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2021		2020
	(in thousands)
Accrued employee compensation	$	25,749	$	10,885
Accrued research and development costs		4,605		3,057
Accrued asset purchases		4,101		2,527
Accrued professional services		2,636		1,325
Other		3,779		2,148
Total accrued liabilities	$	40,870	$	19,942

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Operating Leases

The Company’s operating leases consist of leased facilities for the Company’s headquarter offices, laboratory, and manufacturing space. Also included in operating leases are leases for vehicles, for use by certain of the Company’s employees, which were not material for the periods presented.

In September 2021, the Company entered into an office lease agreement (“3003 Bunker Hill Lease”) for the 3003 Bunker Hill facility which expires in December 2031. Concurrently, the Company entered into a First Amendment to Office Lease (Net) (the “Lease Amendment”) which extended the lease terms of the 5353 Betsy Ross and 5403 Betsy Ross facilities to December 2031. The 5403 Betsy Ross lease (“5403 Lease”) will continue in its existing terms (and with no changes to its terms, including its base rent) until its expiration in August 2022, at which point the leased space under the 5403 Lease will become subject to the terms of the Lease Amendment. The 3003 Bunker Hill Lease and the Lease Amendment contain options to extend the lease term at the respective facilities for up to two additional five-year terms at the then fair market rate. As of December 31, 2021, the Company is not reasonably certain it will exercise these extension options.

The weighted average remaining lease term and discount rate used to measure the Company’s operating lease liabilities were 9.9 years and 5.0%, respectively. The Company estimated the discount rate using the incremental borrowing rate as the rate implicit in the lease was not readily determinable.

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. As of December 31, 2021, the Company has no material finance leases.

Operating lease cost was $2.9 million, $2.2 million and $1.2 million, for the years ended December 31, 2021, 2020, and 2019, respectively.

The following are minimum future rental payments owed under lease agreements which have commenced as of December 31, 2021:

	(in thousands)
2022	$	3,204
2023		4,194
2024		4,289
2025		4,415
2026		4,545
Thereafter		24,664
Total minimum lease payments	$	45,311
Less: imputed interest and adjustments		(15,252	)
Total lease liability	$	30,059

The total minimum future rental payments owed for the 5403 Betsy Ross facility under the terms of the Lease Amendment which has not yet commenced as of December 31, 2021 is $10.8 million.

Term Notes

12 Months Ended

Dec. 31, 2021

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 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 the 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, 2021.

The supplemental term loan matures on December 1, 2023. The Amended Credit Facility provides an interest-only payment period through June 30, 2022.

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.

The Company recorded interest expense of $1.1 million, $1.2 million and $0.9 million, for the years ended December 31, 2021, 2020 and 2019, 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,
	2021			2020
	(in thousands)
Principal amount of term note	$	16,500		$	16,500
Net premium associated with accretion of final payment, and other debt issuance costs		630			119
Term note, current and noncurrent		17,130			16,619
Less: term note, current portion		(5,500	)		(3,300	)
Term note, noncurrent portion	$	11,630		$	13,319

Future minimum payments of principal and estimated payments of interest on the Company’s outstanding variable rate borrowings as of December 31, 2021 are as follows:

Year ending December 31:	(in thousands)
2022		6,045
2023		12,779
Total future payments		18,824
Less: amounts representing interest		(756	)
Less: final payment		(1,568	)
Total principal amount of term note payments	$	16,500

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Section 50
-Paragraph 1C
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1I
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Section 50
-Paragraph 1C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1E
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

Total stock-based compensation was as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Cost of product revenue	$	1,153	$	496	$	268
Research and development		6,240		2,464		943
Sales and marketing		11,043		3,478		972
General and administrative		8,821		3,912		1,463
Total stock-based compensation	$	27,257	$	10,350	$	3,646

Stock-based compensation of $717,000 and $316,000 was capitalized into inventory for the years ended December 31, 2021 and 2020, respectively. No material stock-based compensation was capitalized into inventory for the year ended December 31, 2019. 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
Expected term (in years)		6.08
Expected volatility		42.4%-42.9%
Risk-free interest rate		2.4%-2.6%
Expected dividend yield		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 “2009 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 Equity Incentive Plan (the “2019 Plan”), which became effective in connection with the Company’s initial public offering. 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 (“RSUs”). 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 Board. As of December 31, 2021, the Company had reserved 3,745,216 shares of common stock for issuance under the 2019 Plan.

Stock Options

Option 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, 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
Awards authorized		1,040,530			—
Options exercised		—			(547,155	)		5.57
Options cancelled		15,062			(15,062	)		9.33
Balance, December 31, 2021		3,745,216			1,524,985		$	6.01	5.76	$	262,793
Vested and exercisable, December 31, 2021					1,295,974		$	5.12	5.55	$	224,475
Vested and expected to vest, December 31, 2021					1,524,985		$	6.01	5.76	$	262,793

There were no options granted during the years ended December 31, 2021 and 2020. The weighted-average grant date fair value of options granted during the year ended December 31, 2019, was $6.58. The total grant date fair value of options vested was $1.6 million, $2.3 million and $1.9 million for the years ended December 31, 2021, 2020, and 2019, respectively.

As of December 31, 2021, total unrecognized stock-based compensation related to unvested stock options was $1.0 million, which the Company expects to recognize over a remaining weighted-average period of 0.8 years.

Restricted Stock Units

RSUs are share awards that entitle the holder to receive freely tradable shares of the Company’s common stock upon vesting. 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 Company’s 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 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
RSUs granted		588,305			138.52
RSUs forfeited		(51,986	)		77.13
RSUs vested		(239,213	)		47.18
Balance, December 31, 2021		1,156,683		$	93.27

The total grant date fair value of RSUs vested was $11.3 million, $2.7 million, and $0.1 million, for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, there was $87.6 million of unrecognized stock-based compensation expense related to RSUs to be recognized over a weighted-average period of 2.7 years.

Employee Share Purchase Plan (ESPP)

In February 2019, the Company adopted the 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 $1.3 million, $0.8 million and $0.3 million of stock-based compensation expense related to the ESPP for the years ended December 31, 2021, 2020 and 2019, respectively.

	Years Ended December 31,
	2021	2020	2019
Expected term (in years)	0.5	0.5	0.5
Expected volatility	48.9%-64.8%	44.3%-74.0%	76.9%
Risk-free interest rate	0.1%	0.1%-0.3%	1.9%
Expected dividend yield	0%	0%	0%

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

9. Income Taxes

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

	December 31,
	2021			2020			2019
	(in thousands)
Domestic	$	(9,388	)	$	(65,957	)	$	(51,179	)
Foreign		553			338			132
Total loss before income taxes	$	(8,835	)	$	(65,619	)	$	(51,047	)

Current income tax provision consists of the following:

	December 31,
	2021		2020		2019
	(in thousands)
Domestic	$	84	$	3	$	—
Foreign		217		77		62
Total current income tax provision	$	301	$	80	$	62

The components of the deferred tax assets and liabilities are as follows:

	December 31,
	2021			2020
	(in thousands)
Deferred tax assets:
Net operating loss carryovers	$	85,764		$	73,453
Fixed and intangible assets		512			718
Accruals and reserves		7,603			2,245
Stock-based compensation		5,523			2,060
Research and development credits		4,698			3,379
Contributions		42			42
Lease liability		7,398			2,004
Total deferred tax assets		111,540			83,901
Less valuation allowance		(104,773	)		(82,087	)
Gross deferred tax assets		6,767			1,814
Deferred tax liabilities:
Right-of-use-assets		(6,767	)		(1,814	)
Gross deferred tax liabilities		(6,767	)		(1,814	)
Total net deferred tax assets	$	—		$	—

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

	December 31,
	2021			2020			2019
	(in thousands)
Income tax benefit at federal statutory rate	$	(1,856	)	$	(13,780	)	$	(10,720	)
State and local income taxes net of federal tax benefit		36			(9	)		(9	)
Foreign tax rate differential		101			6			35
Change in valuation allowance		19,027			27,990			14,470
Stock-based compensation		(17,968	)		(13,425	)		(3,403	)
Research and development credits		(808	)		(611	)		(354	)
Section 382 limitation		575			—			—
Equity method investment		1,320			—			—
Other		(126	)		(91	)		43
Total current income tax provision	$	301		$	80		$	62

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 (“NOL”) and other deferred tax assets. The valuation allowance increased by $22.7 million, $27.0 million and $22.8 million during the years ended December 31, 2021, 2020 and 2019, respectively.

As of December 31, 2021, the Company had NOL carryforwards available to reduce future federal, California and other state income of $351.0 million, $54.0 million and $160.6 million, respectively. The federal NOL carryforwards of $78.4 million and $272.6 million begin expiring in 2030 and never expire respectively, the California NOL carryforwards begin expiring in 2031 and other state NOL carryforwards begin expiring in various years, starting in 2029.

As of December 31, 2021, the Company had research and development credit carryforwards of $5.5 million for federal income tax purposes and $5.0 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 NOL carryforward may be subject to an annual limitation due to the ownership change provided by the Internal Revenue Code of 1986, as amended (the “Code”), and similar state provisions. The annual limitation may result in the expiration of the NOL before utilization. The Company has completed a study under Section 382 of the Code through December 31, 2020, and determined there was a $2.4 million loss of federal NOLs and a $0.1 million loss of federal research and development credits as a result of ownership changes. Utilization of the NOL or tax credit carryforwards to offset future taxable income and taxes, respectively, are subject to an annual limitation under the Code and similar state provisions, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term, tax-exempt rate, and then could be subject to additional adjustments such as built-in gain or built-in loss, as required. Any limitation may result in expiration of all or a portion of its NOLs losses and or tax credit carryforwards before utilization.

Uncertain Tax Positions

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

	December 31,
	2021			2020			2019
	(in thousands)
Beginning balance	$	3,746		$	2,586		$	1,896
Additions (Reductions) based on tax positions related to prior years		(79	)		(3	)		—
Additions based on tax positions related to current years		1,554			1,163			690
Balance at end of year	$	5,221		$	3,746		$	2,586

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.

The Company is subject to taxation in the United States, Germany, the United Kingdom (the “UK”), Japan and France. The Company is subject to examination of its income tax returns since inception by U.S. federal and certain state tax authorities due to its NOLs. The income tax returns of the German entity are open to examination for the tax years 2017 and forward. The income tax returns for the entities in Japan, the UK and France are open to examination for the tax years starting 2020, 2021 and 2021, respectively. The Company is not currently under audit with the Internal Revenue Service, or any foreign, 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 NOL 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Revenue

12 Months Ended

Dec. 31, 2021

Disaggregation Of Revenue [Abstract]

Revenue

10. Revenue

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

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Coronary	$	161,463	$	24,586	$	15,621
Peripheral		74,064		41,994		26,325
Other		1,619		1,209		981
Product revenue	$	237,146	$	67,789	$	42,927

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,
	2021		2020		2019
	(in thousands)
United States	$	186,324	$	37,121	$	22,699
Europe		38,571		23,456		17,499
All other countries		12,251		7,212		2,729
Product revenue	$	237,146	$	67,789	$	42,927

- 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=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (b)
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 12
-Subparagraph (e)
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 606
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-Section 50
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Equity Method Investments

12 Months Ended

Dec. 31, 2021

Equity Method Investments And Joint Ventures [Abstract]

Equity Method Investments

11. Equity Method Investments

Genesis Shockwave Private Limited

On March 19, 2021, the Company entered into the Joint Venture Deed (or “JV Agreement”) with Genesis MedTech International Private Limited (“Genesis”) to establish a long-term strategic partnership to develop, manufacture and commercialize certain of the Company’s interventional products in the People’s Republic of China, excluding the Special Administrative Regions of Hong Kong and Macau (“China”). Under the JV Agreement, Genesis Shockwave Private Ltd. (the “JV”) was formed under the laws of Singapore to serve as a joint venture of Genesis and the Company for the purpose of establishing and managing such a strategic partnership.

On the same date, Genesis and the Company entered into a Share Subscription Agreement pursuant to which, among other things, the JV issued (i) 54,900 ordinary shares which represents 55% of total equity of the JV, to Genesis in exchange for a cash contribution of $15.0 million, of which 50% was paid upon signing and the remaining 50% will be due within one year of signing, and (ii) 45,000 ordinary shares which represents 45% of total equity, to the Company as consideration for the Shockwave License Agreement (or “License Agreement”). Under the License Agreement, the Company has agreed to contribute to the JV an exclusive license under certain of the Company’s intellectual property rights to develop, manufacture, distribute and commercialize certain products in China and is entitled to receive royalties on the sales of the licensed products in China. Further, the Company entered into a Distribution Agreement, pursuant to which the Company has agreed to sell certain Company-manufactured products to the JV and/or a to-be formed Chinese subsidiary of the JV for commercialization and distribution in China.

The Company has accounted for its investment in the JV under the equity method of accounting. As of December 31, 2021, the carrying value of the Company’s investment in the JV was $6.0 million. The Company’s share of losses generated by the JV for the year ended December 31, 2021 was $6.3 million which was recorded in share in net loss of equity method investment. The JV has not generated any revenues to date.

The following table summarizes the unaudited balance sheet for the JV:

	December 31,
	2021
Balance sheet:	(in thousands)
Current assets	$	14,854
Current liabilities		(1,539	)
Net assets	$	13,315

The following table summarizes the unaudited results of operations for the JV:

	For the Year Ended December 31,
	2021
	(in thousands)
Revenues	$	—
Loss from operations		14,043
Net loss	$	14,043

Upon execution of the License Agreement, on March 19, 2021, the Company received a 45% equity stake in the JV. The Company determined that the JV met the definition of a customer under Topic 606, and that the promised goods and services of the contribution of the license of intellectual property and associated manufacturing technology transfer to the JV were considered to be a single performance obligation. The transaction price of $12.3 million was estimated by reference to the cash value of the shares which were issued at the formation of the JV.

For the year ended December 31, 2021, the Company sold approximately $184,000 in product to the JV for use in ongoing clinical trials. As of December 31, 2021, approximately $138,000 was owed by the JV to the Company for the sale of the product.

As of December 31, 2021, the associated manufacturing technology transfer to the JV had not yet been completed. The Company maintains a related party contract liability, noncurrent, of $12.3 million for the outstanding performance obligation. The Company expects to satisfy the outstanding performance obligation upon the completion of training provided by the Company to the JV, and successful regulatory approval from the China National Medical Products Administration.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Principles of Consolidation

Use of Estimates

Cash, Cash Equivalents and Restricted Cash

	December 31,
	2021		2020
	(in thousands)
Cash and cash equivalents	$	89,209	$	50,423
Restricted cash		1,665		1,450
Total cash, cash equivalents, and restricted cash	$	90,874	$	51,873

Short-Term Investments

Equity Method 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,
	2021			2020			2019
	(in thousands)
Beginning balance	$	380		$	194		$	76
Amounts charged (reversed) to costs and expenses		(12	)		205			121
Write-offs		(18	)		(19	)		(3	)
Ending balance	$	350		$	380		$	194

Inventory

Property and Equipment

Impairment of Long-Lived Assets

Revenue

Product Revenue

License Revenue

Consideration received in advance of the satisfaction of a performance obligation is recognized as a contract liability. No license revenues have been recognized for the year ended December 31, 2021.

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.

Foreign Currency

net foreign currency transaction gains of $0.3 million and $0.1 million for the years ended December 31, 2020 and 2019, respectively.

Net Loss Per Share

	December 31,
	2021		2020		2019
Common stock options issued and outstanding		1,524,985		2,087,202		3,315,001
Restricted stock units		1,156,683		859,577		280,904
Employee stock purchase plan		10,028		15,251		16,420
Total		2,691,696		2,962,030		3,612,325

Income Taxes

Segment Reporting

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

	December 31,
	2021		2020
	(in thousands)
Cash and cash equivalents	$	89,209	$	50,423
Restricted cash		1,665		1,450
Total cash, cash equivalents, and restricted cash	$	90,874	$	51,873

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,
	2021			2020			2019
	(in thousands)
Beginning balance	$	380		$	194		$	76
Amounts charged (reversed) to costs and expenses		(12	)		205			121
Write-offs		(18	)		(19	)		(3	)
Ending balance	$	350		$	380		$	194

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

	December 31,
	2021		2020		2019
Common stock options issued and outstanding		1,524,985		2,087,202		3,315,001
Restricted stock units		1,156,683		859,577		280,904
Employee stock purchase plan		10,028		15,251		16,420
Total		2,691,696		2,962,030		3,612,325

Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

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, 2021
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	80,155	$	—	$	—	$	80,155
Money market funds		47,541		—		—		47,541
Commercial paper		—		20,472		—		20,472
Corporate bonds		—		11,145		—		11,145
Total assets	$	127,696	$	31,617	$	—	$	159,313

	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

Cash Equivalents and Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2021

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, 2021
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
U.S. Treasury securities	$	80,353	$	—	$	(198	)	$	80,155
Money market funds		47,541		—		—			47,541
Commercial paper		20,472		—		—			20,472
Corporate bonds		11,149		—		(4	)		11,145
Total	$	159,515	$	—	$	(202	)	$	159,313
Reported as:
Cash equivalents								$	47,541
Short-term investments									111,772
Total								$	159,313

	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

Summary of Remaining Contractual Maturities for Available-for-sale Securities

As of December 31, 2021, the fair value of the Company’s available-for-sale securities, by remaining contractual maturities, were as follows (in thousands):

One year or less	$	113,330
Greater than one year and less than two years		45,983
Total	$	159,313

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Inventory

Inventory consists of the following:

	December 31,
	2021		2020
	(in thousands)
Raw material	$	7,685	$	4,995
Work in progress		13,315		6,051
Finished goods		20,326		16,952
Consigned inventory		1,652		1,861
Total inventory	$	42,978	$	29,859

Schedule of Property and Equipment

Property and equipment, net consists of the following:

	December 31,
	2021			2020
	(in thousands)
Equipment	$	6,234		$	3,794
Equipment on loan to customers		1,714			1,756
Office furniture		549			157
Software		742			175
Leasehold improvements		17,742			5,808
Construction in progress		3,544			7,800
Property and equipment, gross		30,525			19,490
Less: accumulated depreciation and amortization		(6,164	)		(3,128	)
Total property and equipment, net	$	24,361		$	16,362

Schedule of Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2021		2020
	(in thousands)
Accrued employee compensation	$	25,749	$	10,885
Accrued research and development costs		4,605		3,057
Accrued asset purchases		4,101		2,527
Accrued professional services		2,636		1,325
Other		3,779		2,148
Total accrued liabilities	$	40,870	$	19,942

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Schedule of Minimum Future Rental Payments

The following are minimum future rental payments owed under lease agreements which have commenced as of December 31, 2021:

	(in thousands)
2022	$	3,204
2023		4,194
2024		4,289
2025		4,415
2026		4,545
Thereafter		24,664
Total minimum lease payments	$	45,311
Less: imputed interest and adjustments		(15,252	)
Total lease liability	$	30,059

Term Notes (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Long Term Debt and Net Premium Balance

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

	December 31,
	2021			2020
	(in thousands)
Principal amount of term note	$	16,500		$	16,500
Net premium associated with accretion of final payment, and other debt issuance costs		630			119
Term note, current and noncurrent		17,130			16,619
Less: term note, current portion		(5,500	)		(3,300	)
Term note, noncurrent portion	$	11,630		$	13,319

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, 2021 are as follows:

Year ending December 31:	(in thousands)
2022		6,045
2023		12,779
Total future payments		18,824
Less: amounts representing interest		(756	)
Less: final payment		(1,568	)
Total principal amount of term note payments	$	16,500

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

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,
	2021		2020		2019
	(in thousands)
Cost of product revenue	$	1,153	$	496	$	268
Research and development		6,240		2,464		943
Sales and marketing		11,043		3,478		972
General and administrative		8,821		3,912		1,463
Total stock-based compensation	$	27,257	$	10,350	$	3,646

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
Expected term (in years)		6.08
Expected volatility		42.4%-42.9%
Risk-free interest rate		2.4%-2.6%
Expected dividend yield		0%

Schedule of Option Activity under 2009 Plan and 2019 Plan

Option 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, 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
Awards authorized		1,040,530			—
Options exercised		—			(547,155	)		5.57
Options cancelled		15,062			(15,062	)		9.33
Balance, December 31, 2021		3,745,216			1,524,985		$	6.01	5.76	$	262,793
Vested and exercisable, December 31, 2021					1,295,974		$	5.12	5.55	$	224,475
Vested and expected to vest, December 31, 2021					1,524,985		$	6.01	5.76	$	262,793

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
RSUs granted		588,305			138.52
RSUs forfeited		(51,986	)		77.13
RSUs vested		(239,213	)		47.18
Balance, December 31, 2021		1,156,683		$	93.27

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

	Years Ended December 31,
	2021	2020	2019
Expected term (in years)	0.5	0.5	0.5
Expected volatility	48.9%-64.8%	44.3%-74.0%	76.9%
Risk-free interest rate	0.1%	0.1%-0.3%	1.9%
Expected dividend yield	0%	0%	0%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

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,
	2021			2020			2019
	(in thousands)
Domestic	$	(9,388	)	$	(65,957	)	$	(51,179	)
Foreign		553			338			132
Total loss before income taxes	$	(8,835	)	$	(65,619	)	$	(51,047	)

Schedule of Current Income Tax Provision

Current income tax provision consists of the following:

	December 31,
	2021		2020		2019
	(in thousands)
Domestic	$	84	$	3	$	—
Foreign		217		77		62
Total current income tax provision	$	301	$	80	$	62

Components of Deferred Tax Assets and Liabilities

The components of the deferred tax assets and liabilities are as follows:

	December 31,
	2021			2020
	(in thousands)
Deferred tax assets:
Net operating loss carryovers	$	85,764		$	73,453
Fixed and intangible assets		512			718
Accruals and reserves		7,603			2,245
Stock-based compensation		5,523			2,060
Research and development credits		4,698			3,379
Contributions		42			42
Lease liability		7,398			2,004
Total deferred tax assets		111,540			83,901
Less valuation allowance		(104,773	)		(82,087	)
Gross deferred tax assets		6,767			1,814
Deferred tax liabilities:
Right-of-use-assets		(6,767	)		(1,814	)
Gross deferred tax liabilities		(6,767	)		(1,814	)
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,
	2021			2020			2019
	(in thousands)
Income tax benefit at federal statutory rate	$	(1,856	)	$	(13,780	)	$	(10,720	)
State and local income taxes net of federal tax benefit		36			(9	)		(9	)
Foreign tax rate differential		101			6			35
Change in valuation allowance		19,027			27,990			14,470
Stock-based compensation		(17,968	)		(13,425	)		(3,403	)
Research and development credits		(808	)		(611	)		(354	)
Section 382 limitation		575			—			—
Equity method investment		1,320			—			—
Other		(126	)		(91	)		43
Total current income tax provision	$	301		$	80		$	62

Schedule of Unrecognized Tax Benefits

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

	December 31,
	2021			2020			2019
	(in thousands)
Beginning balance	$	3,746		$	2,586		$	1,896
Additions (Reductions) based on tax positions related to prior years		(79	)		(3	)		—
Additions based on tax positions related to current years		1,554			1,163			690
Balance at end of year	$	5,221		$	3,746		$	2,586

Revenue (Tables)

12 Months Ended

Dec. 31, 2021

Disaggregation Of Revenue [Abstract]

Schedule of Product Revenue Based on Product Line and Location

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

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Coronary	$	161,463	$	24,586	$	15,621
Peripheral		74,064		41,994		26,325
Other		1,619		1,209		981
Product revenue	$	237,146	$	67,789	$	42,927

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

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
United States	$	186,324	$	37,121	$	22,699
Europe		38,571		23,456		17,499
All other countries		12,251		7,212		2,729
Product revenue	$	237,146	$	67,789	$	42,927

Equity Method Investments (Tables)

12 Months Ended

Dec. 31, 2021

Equity Method Investments And Joint Ventures [Abstract]

Summary of Unaudited Balance Sheet

The following table summarizes the unaudited balance sheet for the JV:

	December 31,
	2021
Balance sheet:	(in thousands)
Current assets	$	14,854
Current liabilities		(1,539	)
Net assets	$	13,315

Summary of Unaudited Results of Operations

The following table summarizes the unaudited results of operations for the JV:

	For the Year Ended December 31,
	2021
	(in thousands)
Revenues	$	—
Loss from operations		14,043
Net loss	$	14,043

Organization and Basis of Presentation - Additional Information (Details) $ in Millions	Dec. 31, 2021 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash, cash equivalents and short-term investments	$ 201.0

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 89,209	$ 50,423
Restricted cash	1,665	1,450
Total cash, cash equivalents, and restricted cash	$ 90,874	$ 51,873	$ 140,495	$ 40,093

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Customer Segment	Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Share in net loss of equity method investment	$ 6,286,000
Notice period for cancellation of agreement	30 days
Defined contribution plan, contribution amount	$ 2,500,000	$ 1,100,000	$ 0
Foreign currency transaction realized and unrealized gain (loss)	$ (800,000)	$ 300,000	$ 100,000
Number of Operating Segments \| Segment	1
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	0	1
Customer \| Revenue Benchmark \| No Customer
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Credit Concentration Risk \| Accounts Receivable \| No Customer
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%
Credit Concentration Risk \| Accounts Receivable \| Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		15.00%

Summary of Significant Accounting Policies - Summary of Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 380	$ 194	$ 76
Amounts charged (reversed) to costs and expenses	(12)	205	121
Write-offs	(18)	(19)	(3)
Ending balance	$ 350	$ 380	$ 194

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,691,696	2,962,030	3,612,325
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	1,524,985	2,087,202	3,315,001
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	1,156,683	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	10,028	15,251	16,420

Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Total assets	$ 159,313	$ 193,384
Level 1
Assets:
Total assets	127,696	161,416
Level 2
Assets:
Total assets	31,617	31,968
U.S. Treasury securities
Assets:
Total assets	80,155	126,363
U.S. Treasury securities \| Level 1
Assets:
Total assets	80,155	126,363
Money Market Funds
Assets:
Total assets	47,541	35,053
Money Market Funds \| Level 1
Assets:
Total assets	47,541	35,053
Commercial Paper
Assets:
Total assets	20,472	31,968
Commercial Paper \| Level 2
Assets:
Total assets	20,472	$ 31,968
Corporate Bonds
Assets:
Total assets	11,145
Corporate Bonds \| Level 2
Assets:
Total assets	$ 11,145

Cash Equivalents and Short-Term Investments - Summary of Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Cash And Cash Equivalents [Line Items]
Cash equivalents, Fair Value	$ 47,541	$ 41,453
Cash equivalents and short-term investments, Amortized Cost Basis	159,515	193,375
Cash equivalents and short-term investments, Unrealized Gains		11
Cash equivalents and short-term investments, Unrealized losses	(202)	(2)
Cash equivalents and short-term investments, Fair Value	159,313	193,384
Short-term investments	111,772	151,931
U.S. Treasury securities
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	80,353	126,354
Short-term investments Unrealized Gains		11
Short-term investments Unrealized Losses	(198)	(2)
Short-term investments, Fair Value	80,155	126,363
Money Market Funds
Cash And Cash Equivalents [Line Items]
Cash equivalents Amortized Cost Basis	47,541	35,053
Cash equivalents, Fair Value	47,541	35,053
Corporate Bonds
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	11,149
Short-term investments Unrealized Losses	(4)
Short-term investments, Fair Value	11,145
Commercial Paper
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	20,472	31,968
Short-term investments, Fair Value	$ 20,472	$ 31,968

Cash Equivalents and Short-Term Investments - Summary of Remaining Contractual Maturities for Available-for-sale Securities (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Cash And Cash Equivalents [Abstract]
One year or less	$ 113,330
Greater than one year and less than two years	45,983
Total	$ 159,313

Cash Equivalents and Short-Term Investments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($)
Cash And Cash Equivalents [Abstract]
Realized gains on cash equivalents and short-term investments	$ 21,000

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw material	$ 7,685	$ 4,995
Work in progress	13,315	6,051
Finished goods	20,326	16,952
Consigned inventory	1,652	1,861
Total inventory	$ 42,978	$ 29,859

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 30,525	$ 19,490
Less: accumulated depreciation and amortization	(6,164)	(3,128)
Total property and equipment, net	24,361	16,362
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,234	3,794
Equipment Loan To Customer
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,714	1,756
Office Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	549	157
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	742	175
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	17,742	5,808
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,544	$ 7,800

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 3,579	$ 1,863	$ 1,337

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued employee compensation	$ 25,749	$ 10,885
Accrued research and development costs	4,605	3,057
Accrued asset purchases	4,101	2,527
Accrued professional services	2,636	1,325
Other	3,779	2,148
Total accrued liabilities	$ 40,870	$ 19,942

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2021 Term	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Operating lease liabilities, weighted average remaining lease term		9 years 10 months 24 days
Operating lease liabilities, weighted average incremental borrowing rate		5.00%
Operating lease cost		$ 2.9	$ 2.2	$ 1.2
3003 Lease
Loss Contingencies [Line Items]
Lease term expiration month and year	2031-12
Number of additional five year term \| Term	2
Operating lease, extended period	5 years
5403 Lease
Loss Contingencies [Line Items]
Lease term expiration month and year	2022-08
Total minimum lease payments		$ 10.8
5403 and 5353 Lease
Loss Contingencies [Line Items]
Extended lease term expiration month and year	2031-12

Commitments and Contingencies - Schedule of Minimum Future Rental Payments (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2022	$ 3,204
2023	4,194
2024	4,289
2025	4,415
2026	4,545
Thereafter	24,664
Total minimum lease payments	45,311
Less: imputed interest and adjustments	(15,252)
Total lease liability	$ 30,059

Term Notes - Additional Information (Details) - USD ($)		12 Months Ended
Term Notes - Additional Information (Details) - USD ($)	Feb. 29, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 28, 2018
Debt Instrument [Line Items]
Debt Amount		$ 16,500,000	$ 16,500,000
Debt, final payment amount		1,568,000
Interest expense		$ 1,096,000	1,212,000	$ 944,000
Loan and Security Agreement
Debt Instrument [Line Items]
Debt, final payment as percentage of original aggregate principal amount		6.75%
Debt, final payment amount		$ 1,000,000.0			$ 1,000,000.0
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 through June 30, 2022.
Interest expense		$ 1,100,000	$ 1,200,000	$ 900,000
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 \| Short Term Notes
Debt Instrument [Line Items]
Debt Amount					15,000,000.0
Loan and Security Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt Amount					$ 2,000,000.0
Termination of Line of Credit Facility	$ 2,000,000.0
Loan and Security Agreement \| Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Line of credit facility termination fee	$ 100,000

Term Notes - Schedule of Long Term Debt and Net Premium Balance (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument Periodic Payment [Abstract]
Principal amount of term note	$ 16,500	$ 16,500
Net premium associated with accretion of final payment, and other debt issuance costs	630	119
Term note, current and noncurrent	17,130	16,619
Less: term note, current portion	(5,500)	(3,300)
Term note, noncurrent portion	$ 11,630	$ 13,319

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

Term Notes - Schedule of Future Minimum and Estimated Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
2022	$ 6,045
2023	12,779
Total future payments	18,824
Less: amounts representing interest	(756)
Less: final payment	(1,568)
Total principal amount of term note payments	$ 16,500	$ 16,500

Stock-Based Compensation - Schedule of Total Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 27,257	$ 10,350	$ 3,646
Cost of Product Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	1,153	496	268
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	6,240	2,464	943
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	11,043	3,478	972
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 8,821	$ 3,912	$ 1,463

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Mar. 06, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses capitalized amount		$ 717,000	$ 316,000	$ 0
Expected dividend yield		0.00%		0.00%
Options granted		0	0	442,858
Weighted-average grant date fair value of options granted				$ 6.58
Grant date fair value of options vested		$ 1,600,000	$ 2,300,000	$ 1,900,000
Unvested stock options		$ 1,000,000.0
Unvested stock options, remaining weighted-average period		9 months 18 days
Stock-based compensation		$ 27,257,000	10,350,000	3,646,000
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 Company’s 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		2 years 8 months 12 days
Grant date fair value of RSU vested		$ 11,300,000	$ 2,700,000	$ 100,000
Number of Shares, RSUs granted		588,305	687,223	288,170
Unrecognized stock-based compensation		$ 87,600,000
2019 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	2,000,430	3,745,216
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
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield		0.00%	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		$ 1,300,000	$ 800,000	$ 300,000

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, 2021	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)		6 years 29 days
Expected volatility, minimum		42.40%
Expected volatility, maximum		42.90%
Risk-free interest rate, minimum		2.40%
Risk-free interest rate, maximum		2.60%
Expected dividend yield	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, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares Available for Grant
Shares Available for Grant, Beginning balance	2,689,624	1,704,244	392,299
Shares Available for Grant, Awards authorized	1,040,530	943,345	2,000,430
Shares Available for Grant, Options expired			(287,600)
Shares Available for Grant, Options granted			(442,858)
Shares Available for Grant, Options cancelled	15,062	42,035	41,973
Shares Available for Grant, Ending balance	3,745,216	2,689,624	1,704,244	392,299
Number of Shares
Number of Shares, Beginning balance	2,087,202	3,315,001	3,636,358
Number of Shares, Options granted	0	0	442,858
Number of Shares, Options exercised	(547,155)	(1,185,764)	(722,242)
Number of Shares, Options cancelled	(15,062)	(42,035)	(41,973)
Number of Shares, Ending balance	1,524,985	2,087,202	3,315,001	3,636,358
Number of Shares, Vested and exercisable	1,295,974
Number of Shares, Vested and expected to vest	1,524,985
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 5.92	$ 5.08	$ 3.54
Weighted-Average Exercise Price Per Share, Options granted			14.69
Weighted-Average Exercise Price Per Share, Options exercised	5.57	3.64	3.10
Weighted-Average Exercise Price Per Share, Options cancelled	9.33	4.45	3.85
Weighted-Average Exercise Price Per Share, Ending balance	6.01	$ 5.92	$ 5.08	$ 3.54
Weighted-Average Exercise Price Per Share, Vested and exercisable	5.12
Weighted-Average Exercise Price Per Share, Vested and expected to vest	$ 6.01
Weighted-Average Remaining Term
Weighted-Average Remaining Term (in years), Balance	5 years 9 months 3 days	6 years 9 months 7 days	7 years 3 months 10 days	7 years 9 months 14 days
Weighted-Average Remaining Term, Vested and exercisable	5 years 6 months 18 days
Weighted-Average Remaining Term, Vested and expected to vest	5 years 9 months 3 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Balance	$ 262,793	$ 204,137	$ 128,744	$ 11,267
Aggregate Intrinsic Value, Vested and exercisable	224,475
Aggregate Intrinsic Value, Vested and expected to vest	$ 262,793

Stock-Based Compensation - Schedule of RSU Activity under 2019 Plan (Details) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Number of Shares, Beginning balance	859,577	280,904
Number of Shares, RSUs granted	588,305	687,223	288,170
Number of Shares, RSUs forfeited	(51,986)	(38,650)	(5,600)
Number of Shares, RSUs vested	(239,213)	(69,900)	(1,666)
Number of Shares, Ending balance	1,156,683	859,577	280,904
Weighted-Average Grant Date Fair Value Per Share
Weighted-Average Grant Date Fair Value Per Share, Beginning balance	$ 48.50	$ 38.12
Weighted-Average Grant Date Fair Value Per Share, RSUs granted	138.52	51.34	$ 38.28
Weighted-Average Grant Date Fair Value Per Share, RSUs forfeited	77.13	41.55	40.01
Weighted-Average Grant Date Fair Value Per Share, RSUs vested	47.18	38.46	59.79
Weighted-Average Grant Date Fair Value Per Share, Ending balance	$ 93.27	$ 48.50	$ 38.12

Stock-Based Compensation - Schedule of Fair Value of ESPP Shares Estimated Using Black-Scholes Option Pricing Model Assumptions (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			6 years 29 days
Expected volatility, minimum			42.40%
Expected volatility, maximum			42.90%
Risk-free interest rate, minimum			2.40%
Risk-free interest rate, maximum			2.60%
Expected dividend yield	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	6 months
Expected volatility, minimum	48.90%	44.30%
Expected volatility			76.90%
Expected volatility, maximum	64.80%	74.00%
Risk-free interest rate, minimum		0.10%
Risk-free interest rate	0.10%		1.90%
Risk-free interest rate, maximum		0.30%
Expected dividend yield	0.00%	0.00%	0.00%

Income Taxes -Schedule of Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (9,388)	$ (65,957)	$ (51,179)
Foreign	553	338	132
Net loss before taxes	$ (8,835)	$ (65,619)	$ (51,047)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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+ Details

Income Taxes - Schedule of Current Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 301	$ 80	$ 62
Domestic Federal
Income Taxes Disclosure [Line Items]
Total current income tax provision	84	3
Foreign Tax Authority
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 217	$ 77	$ 62

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Net operating loss carryovers	$ 85,764	$ 73,453
Fixed and intangible assets	512	718
Accruals and reserves	7,603	2,245
Stock-based compensation	5,523	2,060
Research and development credits	4,698	3,379
Contributions	42	42
Lease liability	7,398	2,004
Total deferred tax assets	111,540	83,901
Less valuation allowance	(104,773)	(82,087)
Gross deferred tax assets	6,767	1,814
Deferred tax liabilities:
Right-of-use-assets	(6,767)	(1,814)
Gross deferred tax liabilities	$ (6,767)	$ (1,814)

Income Taxes - Reconciliation of Statutory Federal Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation
Income tax benefit at federal statutory rate	$ (1,856)	$ (13,780)	$ (10,720)
State and local income taxes net of federal tax benefit	36	(9)	(9)
Foreign tax rate differential	101	6	35
Change in valuation allowance	19,027	27,990	14,470
Stock-based compensation	(17,968)	(13,425)	(3,403)
Research and development credits	(808)	(611)	(354)
Section 382 limitation	575
Equity method investment	1,320
Other	(126)	(91)	43
Total current income tax provision	$ 301	$ 80	$ 62

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes Disclosure [Line Items]
Increase in valuation allowance	$ 22.7	$ 27.0	$ 22.8
Research and development credit carryforwards	0.1
Federal net operating losses	2.4
Domestic Federal
Income Taxes Disclosure [Line Items]
NOL carryforwards	$ 351.0
NOL carryforwards	2030
NOL carryforwards subject to expiration in 2030			78.4
NOL carryforwards never expire			$ 272.6
Research and development credit carryforwards	$ 5.5
California \| State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
NOL carryforwards	$ 54.0
NOL carryforwards	2031
Research and development credit carryforwards	$ 5.0
All Other States \| State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
NOL carryforwards	$ 160.6
NOL carryforwards	2029

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unrecognized tax benefits [Abstract]
Beginning balance	$ 3,746	$ 2,586	$ 1,896
Reductions based on tax positions related to prior years	(79)	(3)
Additions based on tax positions related to current years	1,554	1,163	690
Balance at end of year	$ 5,221	$ 3,746	$ 2,586

Revenue - Schedule of Product Revenue Based on Product Line and Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Product revenue	$ 237,146	$ 67,789	$ 42,927
United States
Disaggregation Of Revenue [Line Items]
Product revenue	186,324	37,121	22,699
Europe
Disaggregation Of Revenue [Line Items]
Product revenue	38,571	23,456	17,499
All Other Countries
Disaggregation Of Revenue [Line Items]
Product revenue	12,251	7,212	2,729
Coronary
Disaggregation Of Revenue [Line Items]
Product revenue	161,463	24,586	15,621
Peripheral
Disaggregation Of Revenue [Line Items]
Product revenue	74,064	41,994	26,325
Other
Disaggregation Of Revenue [Line Items]
Product revenue	$ 1,619	$ 1,209	$ 981

- 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.

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+ Details

Equity Method Investments - Additional Information (Details) - USD ($)		12 Months Ended
	Mar. 19, 2021	Dec. 31, 2021
Schedule Of Equity Method Investments [Line Items]
Equity method investment		$ 5,987,000
Share in net loss of equity method investment		6,286,000
Related party contract liability, noncurrent portion		12,273,000
Joint Venture
Schedule Of Equity Method Investments [Line Items]
Percentage of equity stake received	45.00%
Related party transaction. transaction price	$ 12,300,000
Related party contract liability, noncurrent portion		12,300,000
Related party, sold		184,000
Related party, owned for sale of product		$ 138,000
JV Agreement with Genesis MedTech \| Share Subscription Agreement
Schedule Of Equity Method Investments [Line Items]
Ordinary shares issued	54,900
Equity percentage	55.00%
Cash contribution from exchange of equity	$ 15,000,000.0
Percentage of cash contribution received from exchange of equity upon signing of agreement	50.00%
Percentage of cash contribution receivable from exchange of equity within one year	50.00%
JV Agreement with Genesis MedTech \| License Agreement
Schedule Of Equity Method Investments [Line Items]
Ordinary shares issued	45,000
Equity percentage	45.00%

Equity Method Investments - Summary of Unaudited Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance sheet:
Current assets	$ 285,902	$ 246,300
Current liabilities	(51,628)	$ (25,581)
JV Agreement with Genesis MedTech
Balance sheet:
Current assets	14,854
Current liabilities	(1,539)
Net assets	$ 13,315

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer.

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+ Details

Equity Method Investments - Summary of Unaudited Results of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Equity Method Investments [Line Items]
Product revenue	$ 237,146	$ 67,789	$ 42,927
Loss from operations	(871)	(65,663)	(51,839)
Net loss	(9,136)	$ (65,699)	$ (51,109)
JV Agreement with Genesis MedTech
Schedule Of Equity Method Investments [Line Items]
Loss from operations	14,043
Net loss	$ 14,043

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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