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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2019	Oct. 31, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	SWAV
Entity Registrant Name	ShockWave Medical, Inc.
Entity Central Index Key	0001642545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		28,300,080
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-38829
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0494101
Entity Address, Address Line One	5403 Betsy Ross Drive
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	(510)
Local Phone Number	279-4262
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	ShockWave Medical Inc., common stock, par value $0.001 per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 39,452	$ 39,643
Short-term investments	74,646
Accounts receivable, net	5,551	2,850
Inventory	9,227	5,131
Prepaid expenses and other current assets	2,199	1,112
Total current assets	131,075	48,736
Operating lease right-of-use assets	2,155
Property and equipment, net	4,111	2,619
Other assets	548	2,066
TOTAL ASSETS	137,889	53,421
CURRENT LIABILITIES:
Accounts payable	2,486	1,487
Term notes, current portion	6,667	1,667
Accrued liabilities	9,496	6,217
Lease liability, current portion	742
Total current liabilities	19,391	9,371
Lease liability, noncurrent portion	1,543
Term notes, noncurrent portion	8,705	13,383
Convertible preferred stock warrant liability		313
Other liabilities		136
TOTAL LIABILITIES	29,639	23,203
Commitments and contingencies (Note 6)
Convertible preferred stock		152,806
STOCKHOLDERS’ EQUITY (DEFICIT):
Preferred stock
Common stock	28	2
Additional paid-in capital	271,394	4,275
Accumulated other comprehensive income	57
Accumulated deficit	(163,229)	(126,865)
TOTAL STOCKHOLDERS’ EQUITY (DEFICIT)	108,250	(122,588)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)	$ 137,889	$ 53,421

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Product revenue	$ 11,333	$ 3,600	$ 28,615	$ 7,201
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Operating expenses:
Cost of product revenue	$ 4,401	$ 1,973	$ 11,606	$ 3,946
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 8,368	$ 5,533	$ 22,778	$ 16,579
Sales and marketing	8,192	4,801	21,023	12,611
General and administrative	3,437	1,369	9,684	4,137
Total operating expenses	24,398	13,676	65,091	37,273
Loss from operations	(13,065)	(10,076)	(36,476)	(30,072)
Interest expense	(251)	(158)	(746)	(216)
Change in fair value of warrant liability		(104)	(609)	(53)
Other income, net	385	166	1,518	489
Net loss before taxes	(12,931)	(10,172)	(36,313)	(29,852)
Income tax provision	26	6	51	27
Net loss	(12,957)	(10,178)	(36,364)	(29,879)
Unrealized gain (loss) on available-for-sale securities	(18)		57	1
Total comprehensive loss	$ (12,975)	$ (10,178)	$ (36,307)	$ (29,878)
Net loss per share, basic and diluted	$ (0.46)	$ (5.73)	$ (1.66)	$ (17.15)
Shares used in computing net loss per share, basic and diluted	28,085,821	1,776,249	21,886,396	1,742,572

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (83,292)		$ 2	$ 2,470	$ (1)	$ (85,763)
Temporary equity, Beginning balance, shares at Dec. 31, 2017		17,510,045
Temporary equity, Beginning balance at Dec. 31, 2017		$ 137,469
Beginning balance, shares at Dec. 31, 2017			1,627,032
Exercise of Series A-1 warrants		$ 312
Temporary equity, Exercise of Series A-1 warrants, Shares		52,169
Issuance of common stock warrants	104			104
Exercise of stock options	215			215
Exercise of stock options, Shares			143,422
Unrealized gain (loss) on available-for-sale securities	1				1
Vesting of early exercised options	22			22
Stock-based compensation	273			273
Net loss	(9,594)					(9,594)
Ending balance at Mar. 31, 2018	(92,271)		$ 2	3,084		(95,357)
Temporary equity, Ending balance, shares at Mar. 31, 2018		17,562,214
Temporary equity, Ending balance at Mar. 31, 2018		$ 137,781
Ending balance, shares at Mar. 31, 2018			1,770,454
Beginning balance at Dec. 31, 2017	(83,292)		$ 2	2,470	(1)	(85,763)
Temporary equity, Beginning balance, shares at Dec. 31, 2017		17,510,045
Temporary equity, Beginning balance at Dec. 31, 2017		$ 137,469
Beginning balance, shares at Dec. 31, 2017			1,627,032
Net loss	(29,879)
Ending balance at Sep. 30, 2018	(111,832)		$ 2	3,808		(115,642)
Temporary equity, Ending balance, shares at Sep. 30, 2018		17,579,720
Temporary equity, Ending balance at Sep. 30, 2018		$ 137,886
Ending balance, shares at Sep. 30, 2018			1,810,503
Beginning balance at Mar. 31, 2018	(92,271)		$ 2	3,084		(95,357)
Temporary equity, Beginning balance, shares at Mar. 31, 2018		17,562,214
Temporary equity, Beginning balance at Mar. 31, 2018		$ 137,781
Beginning balance, shares at Mar. 31, 2018			1,770,454
Exercise of Series A-1 warrants		$ 105
Temporary equity, Exercise of Series A-1 warrants, Shares		17,506
Exercise of stock options	60			60
Exercise of stock options, Shares			27,067
Vesting of early exercised options	20			20
Stock-based compensation	312			312
Net loss	(10,107)					(10,107)
Ending balance at Jun. 30, 2018	(101,986)		$ 2	3,476		(105,464)
Temporary equity, Ending balance, shares at Jun. 30, 2018		17,579,720
Temporary equity, Ending balance at Jun. 30, 2018		$ 137,886
Ending balance, shares at Jun. 30, 2018			1,797,521
Exercise of stock options	25			25
Exercise of stock options, Shares			12,982
Vesting of early exercised options	18			18
Stock-based compensation	289			289
Net loss	(10,178)					(10,178)
Ending balance at Sep. 30, 2018	(111,832)		$ 2	3,808		(115,642)
Temporary equity, Ending balance, shares at Sep. 30, 2018		17,579,720
Temporary equity, Ending balance at Sep. 30, 2018		$ 137,886
Ending balance, shares at Sep. 30, 2018			1,810,503
Beginning balance at Dec. 31, 2018	(122,588)		$ 2	4,275		(126,865)
Temporary equity, Beginning balance, shares at Dec. 31, 2018		18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018	152,806	$ 152,806
Beginning balance, shares at Dec. 31, 2018			1,824,852
Exercise of common stock warrants for cash	110			110
Exercise of common stock warrants for cash, shares			50,331
Issuance of common stock upon net exercise of warrants	133			133
Issuance of common stock upon net exercise of warrants, shares			101,744
Conversion of preferred stock to common stock upon initial public offering	152,806		$ 18	152,788
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)
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			789
Issuance of common stock in connection with initial public offering, net of issuance costs of $11.3 million	100,139		$ 7	100,132
Issuance of common stock in connection with initial public offering, net of issuance costs, Shares			6,555,000
Issuance of common stock in connection with private placement	10,000		$ 1	9,999
Issuance of common stock in connection with private placement, shares			588,235
Exercise of stock options	169			169
Exercise of stock options, Shares			80,515
Vesting of early exercised options	18			18
Stock-based compensation	412			412
Offering costs related to the initial public offering	(11,300)
Adjustment for fractional shares resulting from reverse stock split	(3)			(3)
Adjustment for fractional shares resulting from reverse stock split			(114)
Net loss	(12,799)					(12,799)
Ending balance at Mar. 31, 2019	129,186		$ 28	268,822		(139,664)
Ending balance, shares at Mar. 31, 2019			27,870,891
Beginning balance at Dec. 31, 2018	(122,588)		$ 2	4,275		(126,865)
Temporary equity, Beginning balance, shares at Dec. 31, 2018		18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018	$ 152,806	$ 152,806
Beginning balance, shares at Dec. 31, 2018			1,824,852
Exercise of stock options, Shares	386,309
Net loss	$ (36,364)
Ending balance at Sep. 30, 2019	108,250		$ 28	271,394	57	(163,229)
Ending balance, shares at Sep. 30, 2019			28,255,893
Beginning balance at Mar. 31, 2019	129,186		$ 28	268,822		(139,664)
Beginning balance, shares at Mar. 31, 2019			27,870,891
Issuance of common stock upon net exercise of warrants, shares			79,208
Exercise of stock options	148			148
Exercise of stock options, Shares			73,608
Unrealized gain (loss) on available-for-sale securities	75				75
Vesting of early exercised options	9			9
Stock-based compensation	818			818
Offering costs related to the initial public offering	(215)			(215)
Net loss	(10,608)					(10,608)
Ending balance at Jun. 30, 2019	119,413		$ 28	269,582	75	(150,272)
Ending balance, shares at Jun. 30, 2019			28,023,707
Exercise of stock options	706			706
Exercise of stock options, Shares			232,186
Unrealized gain (loss) on available-for-sale securities	(18)				(18)
Stock-based compensation	1,106			1,106
Net loss	(12,957)					(12,957)
Ending balance at Sep. 30, 2019	$ 108,250		$ 28	$ 271,394	$ 57	$ (163,229)
Ending balance, shares at Sep. 30, 2019			28,255,893

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019
Statement Of Stockholders Equity [Abstract]
Issuance costs, initial public offering	$ 215	$ 11,300

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (36,364)	$ (29,879)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	854	466
Stock-based compensation	2,336	874
Amortization of right-of-use assets	739
Accretion of discount on available-for-sale securities	(542)
Loss on write down of fixed assets	90	25
Change in fair value of warrant liability	609	53
Amortization of debt issuance costs	322	107
Changes in operating assets and liabilities:
Accounts receivable	(2,701)	(2,016)
Inventory	(4,096)	(2,687)
Prepaid expenses and other current assets	(1,087)	(143)
Other assets	(1)	(9)
Accounts payable	884	(187)
Accrued and other current liabilities	4,169	1,720
Lease liabilities	(749)
Other liabilities		25
Net cash used in operating activities	(35,537)	(31,651)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(106,347)
Proceeds from maturities of available-for-sale securities	32,300	1,807
Purchase of property and equipment	(2,287)	(1,130)
Net cash (used in) provided by investing activities	(76,334)	677
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 term loans		9,988
Proceeds from stock option exercises	1,023	400
Proceeds from warrant exercises	110	101
Net cash provided by financing activities	111,680	10,489
Net decrease in cash, cash equivalents and restricted cash	(191)	(20,485)
Cash, cash equivalents and restricted cash at beginning of period	40,093	51,923
Cash, cash equivalents and restricted cash equivalents at end of period	39,902	31,438
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	420	68
Income tax paid	120	5
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued on conversion of convertible preferred stock	152,806
Issuance of Series A-1 convertible preferred stock on net exercise of warrants		316
Common stock issued upon net exercise of warrants	133
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	73
Property and equipment purchases included in accounts payable and accrued liabilities	$ 204	180
Issuance of common stock warrants in connection with debt financing		$ 104

Organization and Basis of Presentation

9 Months Ended

Sep. 30, 2019

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 a subsidiary in Germany.

Initial Public Offering

On March 11, 2019, the Company completed an initial public offering (“IPO”) of its common stock. As part of the IPO, the Company issued and sold 6,555,000 shares of its common stock, which included 855,000 shares sold pursuant to the exercise of the underwriters’ over-allotment option, at a public offering price of $17.00 per share. The Company received net proceeds of approximately $99.9 million from the IPO, after deducting underwriters’ discounts and commissions of $7.1 million and offering costs of $4.4 million, of which $1.5 million was incurred as of December 31, 2018. Prior to the completion of the IPO, all shares of Series A, A-1, B, C and D convertible preferred stock then outstanding were converted into 18,670,259 shares of common stock on a one-to-one basis.

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

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

Reverse Stock Split

In February 2019, the Company’s board of directors approved an amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock and convertible preferred stock on a 12.2-for-one basis (the “Reverse Stock Split”). The par values of the common stock and convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All references to common stock, convertible preferred stock, warrants to purchase common stock, warrants to purchase convertible preferred stock, options to purchase common stock, early exercised options, share data, per share data and related information contained in the financial statements have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. The number of shares of the Company’s common stock contained in the financial statements includes fractional shares resulting from the Reverse Stock Split, aggregating to 45 whole shares of common stock and 69 whole shares of preferred stock as of December 31, 2018, which fractional shares were settled in cash in fiscal 2019.

Need for Additional Capital

The Company has incurred significant losses and has negative cash flows from operations. As of September 30, 2019, the Company had an accumulated deficit of $163.2 million. Management expects to continue to incur additional substantial losses for the foreseeable future.

As of September 30, 2019, the Company had cash, cash equivalents and short-term investments of $114.1 million, which are available to fund future operations. The Company believes that its cash, cash equivalents and short-term investments as of September 30, 2019, will be sufficient for the Company to continue as a going concern for at least 12 months from the date the unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”). The Company’s future capital requirements will depend on many factors, including its growth rate, the timing and extent of its spending to support research and development activities and the timing and cost of establishing additional sales and marketing capabilities.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of SEC regarding interim financial reporting.

The interim condensed consolidated financial statements are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position, results of operations and cash flows. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the prospectus dated March 6, 2019 (“Prospectus”) that forms a part of the Company's Registration Statements on Form S-1 (File No. 333-229590), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended.

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.

Restricted cash as of September 30, 2019 and December 31, 2018 relates to a letter of credit established for a lease entered into in May 2018 and is recorded as other assets on the condensed consolidated balance sheets.

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

	September 30, 2019		December 31, 2018
	(in thousands)
Cash and cash equivalents	$	39,452	$	39,643
Restricted cash		450		450
Total cash, cash equivalents, and restricted cash	$	39,902	$	40,093

Short-Term Investments

Short-term investments have been classified as available-for-sale and are carried at estimated fair value 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.

Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Realized gains and losses and declines in fair value judged to be other than temporary, 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.

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.

Leases

The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) using the modified retrospective approach with a cumulative-effect adjustment as of January 1, 2019.

Upon adoption of Topic 842, on January 1, 2019, the Company recorded operating right-of-use assets of $2.9 million and operating lease liabilities of $3.0 million and derecognized the deferred rent liability of $0.1 million. Results for the three and nine months ended September 30, 2019 are presented under Topic 842. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840).

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

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

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

Deferred Offering Costs

Offering costs, consisting of legal, accounting, printer and filing fees related to the IPO, were deferred until the completion of the IPO. As of December 31, 2018, $1.5 million of deferred offering costs were recorded as other assets on the condensed consolidated balance sheet. In March 2019, upon the closing of the IPO, the deferred costs were offset against the Company’s IPO proceeds.

Convertible Preferred Stock Warrant Liability

The Company has accounted for its freestanding warrants to purchase shares of the Company’s convertible preferred stock as liabilities at fair value upon issuance primarily because the shares underlying the warrants contain contingent redemption features outside the control of the Company. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as the change in fair value of warrant liability. The carrying value of the warrants will continue to be adjusted until such time as these instruments are exercised, expire or convert into warrants to purchase shares of the Company’s common stock upon the completion of a liquidation event, including the completion of the IPO, which occurred on March 11, 2019. At that time, the preferred stock warrant liability was reclassified to additional paid-in capital, a component of stockholders’ equity (deficit).

Revenue

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

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

For products sold through direct sales representatives, control is transferred upon delivery to customers. For products sold to distributors internationally and certain customers that purchase stocking orders in the United States, control is transferred upon shipment or delivery to the customer’s named location, based on the contractual shipping terms. For consignment inventory, control is transferred at the time the IVL catheters are consumed in a procedure.

The Company generally provides 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.

Financial Instruments and Fair Value Measurements

9 Months Ended

Sep. 30, 2019

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:

	September 30, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	58,006	$	—	$	—	$	58,006
Money market funds		19,987		—		—		19,987
Reverse repurchase agreements		—		10,601		—		10,601
Commercial paper		—		8,562		—		8,562
Corporate bonds		—		8,078		—		8,078
Total assets	$	77,993	$	27,241	$	—	$	105,234

	December 31, 2018
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	21,680	$	—	$	—	$	21,680
Total assets	$	21,680	$	—	$	—	$	21,680
Liabilities:
Convertible preferred stock warrant liability	$	—	$	—	$	313	$	313
Total liabilities	$	—	$	—	$	313	$	313

There were no transfers between Levels 1, 2 or 3 for the periods presented.

The change in the fair value of the warrant liability for the nine months ended September 30, 2019 is summarized below (in thousands):

Balance at December 31, 2018	$	313
Change in fair value of warrant liability		609
Net exercise of warrants		(133	)
Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO		(789	)
Balance at September 30, 2019	$	—

The change in the fair value of the warrant liability for the nine months ended September 30, 2018 is summarized below (in thousands):

Balance at December 31, 2017	$	577
Exercise of warrants		(316	)
Expiration of warrants, included in change in fair value of warrant liability		(133	)
Change in fair value of warrant liability		186
Balance at September 30, 2018	$	314

The valuation of the Company’s convertible preferred stock warrant liability contains unobservable inputs that reflect the Company’s own assumptions for which there is little, if any, market activity for at the measurement date. Accordingly, the Company’s convertible preferred stock warrant liability is measured at fair value on a recurring basis using unobservable inputs and are classified as Level 3 inputs, and any change in fair value is recognized as change in fair value of warrant liability in the condensed consolidated statements of operations and comprehensive loss.

The fair value of the warrants, which were converted to common stock warrants upon the closing of the IPO in March 2019, was determined using the Black-Scholes option pricing model and the following assumptions:

	Nine Months Ended September 30,
	2019		2018
Expected term (in years)		5.28	5.71-6.21
Expected volatility	43.9%		42.8%
Risk-free interest rate	2.49%		2.62-2.85%
Expected dividend yield	0%		0%

- 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

9 Months Ended

Sep. 30, 2019

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:

	September 30, 2019
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
U.S. Treasury securities	$	57,959	$	47	$	—	$	58,006
Money market funds		19,987		—		—		19,987
Reverse repurchase agreements		10,601		—		—		10,601
Commercial paper		8,562		—		—		8,562
Corporate bonds		8,068		10		—		8,078
Total	$	105,177	$	57	$	—	$	105,234
Reported as:
Cash equivalents							$	30,588
Short-term investments								74,646
Total							$	105,234

	December 31, 2018
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
Money market funds	$	21,680	$	—	$	—	$	21,680
Total	$	21,680	$	—	$	—	$	21,680
Reported as:
Cash equivalents							$	21,680
Total							$	21,680

The Company recognized no material gains or losses on its cash equivalents and short-term investments in the periods presented.

Balance Sheet Components

9 Months Ended

Sep. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

5. Balance Sheet Components

Inventory

Inventory consists of the following:

	September 30,		December 31,
	2019		2018
	(in thousands)
Raw material	$	2,169	$	1,084
Work in progress		850		634
Finished goods		4,451		2,313
Consigned inventory		1,757		1,100
Total inventory	$	9,227	$	5,131

Accrued Liabilities

Accrued liabilities consist of the following:

	September 30,		December 31,
	2019		2018
	(in thousands)
Accrued employee compensation	$	5,984	$	3,135
Accrued research and development costs		1,844		1,115
Accrued professional services		856		1,391
Other		812		576
Total accrued liabilities	$	9,496	$	6,217

Commitments and Contingencies

9 Months Ended

Sep. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Operating Leases

In August 2012, the Company entered into a lease for office space located in Fremont, California. In October 2018, the Company extended the term of the lease to June 30, 2019 and in February 2019, the Company exercised the option to extend the lease further until September 30, 2019. The lease expired on September 30, 2019. The Company was using the facility for office, manufacturing and research and development purposes.

In May 2018, the Company entered into a new lease agreement for office and laboratory space which consist of approximately 35,000 square feet located in Santa Clara, California. The lease term commenced in September 2018 and ends in August 2022. In connection with the lease, the Company maintains a letter of credit in the amount of $0.5 million, which is secured by restricted cash recorded as other assets on the condensed consolidated balance sheets. In connection with the lease, the Company has an operating lease right-of-use asset of $2.2 million as of September 30, 2019 and an aggregate lease liability of $2.2 million on its condensed consolidated balance sheet. The remaining lease term is two years and ten months.

The Company also leases vehicles for use by employees. In connection with the vehicle leases, the Company has an operating lease right-of-use asset of $47,000 as of September 30, 2019 and an aggregate lease liability of $47,000 on its condensed consolidated balance sheet. The weighted average remaining lease term is 8 months.

The weighted average incremental borrowing rate used to measure the operating lease liability is 6.93%.

Rent expense for the three months ended September 30, 2019 and 2018 was $0.3 million and $0.2 million, respectively. Rent expense for the nine months ended September 30, 2019 and 2018 was $0.9 million and $0.5 million, respectively.

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

The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of September 30, 2019:

	(in thousands)
Remainder of 2019	$	222
2020		861
2021		855
2022		581
Total minimum lease payments	$	2,519
Less: imputed interest		(234	)
Total lease liability	$	2,285

Convertible Preferred Stock and Stockholders’ Equity (Deficit)

9 Months Ended

Sep. 30, 2019

Stockholders Equity [Abstract]

Convertible Preferred Stock and Stockholders’ Equity (Deficit)

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

Convertible Preferred Stock

Immediately prior to the closing of the Company's IPO, 18,670,259 shares of outstanding convertible preferred stock converted into 18,670,259 shares of common stock. As discussed in Note 1, the fractional shares resulting from the Reverse Stock Split, aggregating to 45 whole shares of common stock and 69 whole shares of convertible preferred stock were settled in cash in fiscal 2019.

Preferred Stock

The Company’s amended and restated certificate of incorporation, which became effective upon the completion of the IPO, authorizes 5,000,000 shares of preferred stock, of which no shares were issued or outstanding as of September 30, 2019.

Preferred Stock Warrants

Upon the closing of the IPO, all of the outstanding convertible preferred stock warrants were converted into 54,903 common stock warrants, which resulted in the reclassification of the convertible preferred stock warrant liability of $0.8 million to additional paid-in capital. In April 2019, all of these common stock warrants were net exercised into 49,321 shares of common stock.

Common Stock Warrants

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

In February 2018, in connection with the execution of a Loan and Security Agreement with Silicon Valley Bank for a term loan and revolving line of credit (the “2018 Loan and Security Agreement”), the Company issued warrants to purchase shares of the Company’s common stock. In April 2019, all of these common stock warrants were net exercised into 29,887 shares of common stock.

The key terms of the outstanding common stock warrants are summarized in the following table:

	Warrants Outstanding September 30, 2019		Warrants Outstanding December 31, 2018		Exercise Price		Expiration
Related party common stock warrants		—		141,778	$	2.196	May 2025
Common stock warrants issued in connection with the 2018 Loan and Security Agreement		—		34,440	$	4.026	February 2028
Total common stock warrants		—		176,218

Stock-Based Compensation

9 Months Ended

Sep. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

Total stock-based compensation was as follows:

	Three Months September 30,				Nine Months September 30,
	2019		2018		2019		2018
	(in thousands)				(in thousands)
Cost of product revenue	$	81	$	7	$	156	$	38
Research and development		307		47		582		146
Sales and marketing		288		66		597		185
General and administrative		430		169		1,001		505
Total stock-based compensation	$	1,106	$	289	$	2,336	$	874

Determination of Fair Value

The Company estimates the grant-date fair value of the Company’s option awards using the Black-Scholes option pricing model. The assumptions for the Black-Scholes model for the nine months ended September 30, 2019 and 2018 were as follows:

	Nine Months Ended September 30,
	2019	2018
Expected term (in years)	6.08	6.08
Expected volatility	42.4%-42.9%	40.8%-45.9%
Risk-free interest rate	2.4%-2.6%	1.9%-2.9%
Expected dividend yield	0%	0

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 Board had the authority to issue stock options to employees, directors and consultants.

In February 2019, the Company adopted the 2019 Stock Option and Incentive Plan (the “2019 Plan”), which became effective in connection with the IPO. As a result, effective as of March 6, 2019, the Company may not grant any additional awards under the 2009 Plan. The 2009 Plan will continue to govern outstanding equity awards granted thereunder. The Company has initially reserved 2,000,430 shares of common stock for the issuance of a variety of awards under the 2019 Plan, including stock options, stock appreciation rights, awards of restricted stock and awards of restricted stock units. In addition, the number of shares of common stock reserved for issuance under the 2019 Plan will automatically increase on the first day of January for a period of up to ten years, commencing on January 1, 2020, in an amount equal to 3% of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors. As of September 30, 2019, there were 1,470,192 shares available for issuance under the 2019 Plan.

Stock Options

Option activity under the 2009 Plan and 2019 Plan is set forth below:

	Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Balance, December 31, 2018		3,636,358		$	3.54		7.79	$	11,267
Options granted		442,858			14.69
Options exercised		(386,309	)		2.65
Options forfeited		(34,471	)		3.49
Balance, September 30, 2019		3,658,436		$	4.95	7.52		$	91,399
Vested and exercisable, September 30, 2019		1,831,368		$	3.14	6.59		$	49,068

Restricted Stock Units

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

RSU activity under the 2019 Plan is set forth below:

	Number of Shares			Weighted- Average Grant Date Fair Value Per Share
Balance, December 31, 2018		—		$	—
RSUs granted		229,450			38.26
RSUs forfeited		(2,900	)		37.51
Balance, September 30, 2019		226,550		$	38.27

Employee Share Purchase Plan (ESPP)

In February 2019, the Company adopted the 2019 Employee Stock Purchase Plan (“ESPP”), which became effective as of March 6, 2019. The Company has initially reserved 300,650 shares of common stock for purchase under the ESPP. 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. The first offering period began on September 1, 2019 and will end on February 29, 2020. 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 Company’s Compensation Committee, in its sole discretion.

The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. The Company recorded $64,000 of stock-based compensation expense related to the ESPP for the three and nine months ended September 30, 2019.

Net Loss Per Share

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

9. Net Loss Per Share

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

	September 30,
	2019		2018
	(in thousands)
Convertible preferred stock on an as-converted basis		—		17,579,720
Common stock options issued and outstanding		3,658,436		3,313,257
Restricted stock units		226,550		—
Early exercised options subject to future vesting		—		21,620
Convertible preferred stock warrants		—		54,903
Common stock warrants		—		176,218
Total		3,884,986		21,145,718

Segment and Geographic Information

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Segment and Geographic Information

10. Segment and Geographic Information

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
	(in thousands)				(in thousands)
United States	$	6,246	$	2,053	$	15,054	$	4,476
Germany		873		439		2,389		958
Rest of Europe		3,428		995		9,473		1,597
All other countries		786		113		1,699		170
Product revenue	$	11,333	$	3,600	$	28,615	$	7,201

As of September 30, 2019 and December 31, 2018, the Company’s long-lived assets are all held in the United States with the exception of certain equipment on loan to customers held internationally, which was not material as of each period end.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

Cash, Cash Equivalents, and Restricted Cash

	September 30, 2019		December 31, 2018
	(in thousands)
Cash and cash equivalents	$	39,452	$	39,643
Restricted cash		450		450
Total cash, cash equivalents, and restricted cash	$	39,902	$	40,093

Short-Term Investments

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.

Leases

The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) using the modified retrospective approach with a cumulative-effect adjustment as of January 1, 2019.

Deferred Offering Costs

Convertible Preferred Stock Warrant Liability

Revenue

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

	September 30, 2019		December 31, 2018
	(in thousands)
Cash and cash equivalents	$	39,452	$	39,643
Restricted cash		450		450
Total cash, cash equivalents, and restricted cash	$	39,902	$	40,093

Financial Instruments and Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

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:

	September 30, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
U.S. Treasury securities	$	58,006	$	—	$	—	$	58,006
Money market funds		19,987		—		—		19,987
Reverse repurchase agreements		—		10,601		—		10,601
Commercial paper		—		8,562		—		8,562
Corporate bonds		—		8,078		—		8,078
Total assets	$	77,993	$	27,241	$	—	$	105,234

	December 31, 2018
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	21,680	$	—	$	—	$	21,680
Total assets	$	21,680	$	—	$	—	$	21,680
Liabilities:
Convertible preferred stock warrant liability	$	—	$	—	$	313	$	313
Total liabilities	$	—	$	—	$	313	$	313

Schedule of Change in the Fair Value of the Warrant Liability

The change in the fair value of the warrant liability for the nine months ended September 30, 2019 is summarized below (in thousands):

Balance at December 31, 2018	$	313
Change in fair value of warrant liability		609
Net exercise of warrants		(133	)
Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO		(789	)
Balance at September 30, 2019	$	—

The change in the fair value of the warrant liability for the nine months ended September 30, 2018 is summarized below (in thousands):

Balance at December 31, 2017	$	577
Exercise of warrants		(316	)
Expiration of warrants, included in change in fair value of warrant liability		(133	)
Change in fair value of warrant liability		186
Balance at September 30, 2018	$	314

Schedule of Fair Value of Warrants Determined Using the Black-Scholes Option Pricing Model

	Nine Months Ended September 30,
	2019		2018
Expected term (in years)		5.28	5.71-6.21
Expected volatility	43.9%		42.8%
Risk-free interest rate	2.49%		2.62-2.85%
Expected dividend yield	0%		0%

Cash Equivalents and Short-Term Investments (Tables)

9 Months Ended

Sep. 30, 2019

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:

	September 30, 2019
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
U.S. Treasury securities	$	57,959	$	47	$	—	$	58,006
Money market funds		19,987		—		—		19,987
Reverse repurchase agreements		10,601		—		—		10,601
Commercial paper		8,562		—		—		8,562
Corporate bonds		8,068		10		—		8,078
Total	$	105,177	$	57	$	—	$	105,234
Reported as:
Cash equivalents							$	30,588
Short-term investments								74,646
Total							$	105,234

	December 31, 2018
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
Money market funds	$	21,680	$	—	$	—	$	21,680
Total	$	21,680	$	—	$	—	$	21,680
Reported as:
Cash equivalents							$	21,680
Total							$	21,680

Balance Sheet Components (Tables)

9 Months Ended

Sep. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Inventory

Inventory consists of the following:

	September 30,		December 31,
	2019		2018
	(in thousands)
Raw material	$	2,169	$	1,084
Work in progress		850		634
Finished goods		4,451		2,313
Consigned inventory		1,757		1,100
Total inventory	$	9,227	$	5,131

Schedule of Accrued Liabilities

Accrued liabilities consist of the following:

	September 30,		December 31,
	2019		2018
	(in thousands)
Accrued employee compensation	$	5,984	$	3,135
Accrued research and development costs		1,844		1,115
Accrued professional services		856		1,391
Other		812		576
Total accrued liabilities	$	9,496	$	6,217

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Schedule of Carrying Value of Operating Lease Liabilities

The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of September 30, 2019:

	(in thousands)
Remainder of 2019	$	222
2020		861
2021		855
2022		581
Total minimum lease payments	$	2,519
Less: imputed interest		(234	)
Total lease liability	$	2,285

Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Tables)

9 Months Ended

Sep. 30, 2019

Stockholders Equity [Abstract]

Summary of Key Terms of Outstanding Common Stock Warrants

The key terms of the outstanding common stock warrants are summarized in the following table:

	Warrants Outstanding September 30, 2019		Warrants Outstanding December 31, 2018		Exercise Price		Expiration
Related party common stock warrants		—		141,778	$	2.196	May 2025
Common stock warrants issued in connection with the 2018 Loan and Security Agreement		—		34,440	$	4.026	February 2028
Total common stock warrants		—		176,218

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Total Stock-Based Compensation

Total stock-based compensation was as follows:

	Three Months September 30,				Nine Months September 30,
	2019		2018		2019		2018
	(in thousands)				(in thousands)
Cost of product revenue	$	81	$	7	$	156	$	38
Research and development		307		47		582		146
Sales and marketing		288		66		597		185
General and administrative		430		169		1,001		505
Total stock-based compensation	$	1,106	$	289	$	2,336	$	874

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

	Nine Months Ended September 30,
	2019	2018
Expected term (in years)	6.08	6.08
Expected volatility	42.4%-42.9%	40.8%-45.9%
Risk-free interest rate	2.4%-2.6%	1.9%-2.9%
Expected dividend yield	0%	0

Schedule of Option Activity under 2009 Plan and 2019 Plan

Stock Options

Option activity under the 2009 Plan and 2019 Plan is set forth below:

	Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Balance, December 31, 2018		3,636,358		$	3.54		7.79	$	11,267
Options granted		442,858			14.69
Options exercised		(386,309	)		2.65
Options forfeited		(34,471	)		3.49
Balance, September 30, 2019		3,658,436		$	4.95	7.52		$	91,399
Vested and exercisable, September 30, 2019		1,831,368		$	3.14	6.59		$	49,068

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		229,450			38.26
RSUs forfeited		(2,900	)		37.51
Balance, September 30, 2019		226,550		$	38.27

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

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

	September 30,
	2019		2018
	(in thousands)
Convertible preferred stock on an as-converted basis		—		17,579,720
Common stock options issued and outstanding		3,658,436		3,313,257
Restricted stock units		226,550		—
Early exercised options subject to future vesting		—		21,620
Convertible preferred stock warrants		—		54,903
Common stock warrants		—		176,218
Total		3,884,986		21,145,718

Segment and Geographic Information (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Schedule of Product Revenue Based on Location

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
	(in thousands)				(in thousands)
United States	$	6,246	$	2,053	$	15,054	$	4,476
Germany		873		439		2,389		958
Rest of Europe		3,428		995		9,473		1,597
All other countries		786		113		1,699		170
Product revenue	$	11,333	$	3,600	$	28,615	$	7,201

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 11, 2019 USD ($) $ / shares shares	Apr. 30, 2019 shares	Jun. 30, 2019 shares	Mar. 31, 2019 shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Mar. 05, 2019 shares
Organization and Basis of Presentation [Line Items]
Entity incorporation, date of incorporation					Jun. 17, 2009
Net proceeds from IPO, after deducting underwriters’ discounts and commissions \| $	$ 7,100
Common stock, conversion basis					one-to-one basis
Stock split, conversion ratio					12.2
Stockholders' equity, reverse stock split					The Company’s common stock and convertible preferred stock on a 12.2-for-one basis (the “Reverse Stock Split”)
Accumulated deficit \| $					$ (163,229)	$ (126,865)
Cash, cash equivalents and short-term investments \| $					$ 114,100
Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued				6,555,000
Proceeds from initial public offering \| $	$ 99,900
Issuance of common stock upon net exercise of warrants, shares	101,744	29,887	79,208	101,744
Fractional shares issued in reverse stock split					45	45
Warrants
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion	54,903
Preferred Stock
Organization and Basis of Presentation [Line Items]
Fractional shares issued in reverse stock split						69
Initial Public Offering
Organization and Basis of Presentation [Line Items]
Common stock issued	6,555,000
Common stock, offering price per share \| $ / shares	$ 17.00
Offering costs \| $	$ 4,400
Stock split, conversion ratio	1
Initial Public Offering \| Common Stock
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion							18,670,259
Over Allotment Option
Organization and Basis of Presentation [Line Items]
Common stock issued	855,000
Offering costs \| $						$ 1,500
Private Placement
Organization and Basis of Presentation [Line Items]
Common stock issued	588,235
Proceeds from issuance of common stock \| $	$ 10,000

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 39,452	$ 39,643
Restricted cash	450	450
Total cash, cash equivalents, and restricted cash	$ 39,902	$ 40,093	$ 31,438	$ 51,923

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets		$ 2,155
Operating lease liabilities		$ 2,285
Notice period for cancellation of agreement		30 days
Other Assets
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs			$ 1,500
Adoption of Topic 842
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 2,900
Operating lease liabilities	3,000
Derecognized the deferred rent liability	$ (100)

Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
ASSETS
Total assets	$ 105,234	$ 21,680
Liabilities:
Total liabilities		313
Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		313
Reverse Repurchase Agreements
ASSETS
Total assets	10,601
U.S. Treasury securities
ASSETS
Total assets	58,006
Money Market Funds
ASSETS
Total assets	19,987	21,680
Commercial paper
ASSETS
Total assets	8,562
Corporate bonds
ASSETS
Total assets	8,078
Level 1
ASSETS
Total assets	77,993	21,680
Level 1 \| U.S. Treasury securities
ASSETS
Total assets	58,006
Level 1 \| Money Market Funds
ASSETS
Total assets	19,987	21,680
Level 2
ASSETS
Total assets	27,241
Level 2 \| Reverse Repurchase Agreements
ASSETS
Total assets	10,601
Level 2 \| Commercial paper
ASSETS
Total assets	8,562
Level 2 \| Corporate bonds
ASSETS
Total assets	$ 8,078
Level 3
Liabilities:
Total liabilities		313
Level 3 \| Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		$ 313

Financial Instruments and Fair Value Measurements - Schedule of Change in the Fair Value of the Warrant Liability (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Beginning balance	$ 313	$ 577
Net exercise of warrants	(133)	(316)
Expiration of warrants, included in change in fair value of warrant liability		(133)
Change in fair value of warrant liability	609	186
Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO	$ (789)
Ending balance		$ 314

Financial Instruments and Fair Value Measurements - Schedule of Fair Value of Warrants Determined Using the Black-Scholes Option Pricing Model (Details)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Expected term (in years)	5 years 3 months 10 days
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Expected term (in years)		5 years 8 months 15 days
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Expected term (in years)		6 years 2 months 15 days
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	43.9	42.8
Risk-free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	2.49
Risk-free Interest Rate \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input		2.62
Risk-free Interest Rate \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input		2.85
Expected Dividend Yield
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	0	0

Cash Equivalents and Short-Term Investments - Summary of Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash And Cash Equivalents [Line Items]
Cash equivalents Amortized Cost Basis		$ 21,680
Cash equivalents, Fair Value	$ 30,588	21,680
Cash equivalents and short-term investments, Cost Basis	105,177
Cash equivalents and short-term investments, Unrealized Gains	57
Cash equivalents and short-term investments, Fair Value	105,234
Short-term investments	74,646
U.S. Treasury securities
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	57,959
Short-term investments Unrealized Gains	47
Short-term investments, Fair Value	58,006
Reverse Repurchase Agreements
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	10,601
Short-term investments, Fair Value	10,601
Commercial paper
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	8,562
Short-term investments, Fair Value	8,562
Corporate bonds
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	8,068
Short-term investments Unrealized Gains	10
Short-term investments, Fair Value	8,078
Money Market Funds
Cash And Cash Equivalents [Line Items]
Cash equivalents Amortized Cost Basis	19,987	21,680
Cash equivalents, Fair Value	$ 19,987	$ 21,680

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw material	$ 2,169	$ 1,084
Work in progress	850	634
Finished goods	4,451	2,313
Consigned inventory	1,757	1,100
Total inventory	$ 9,227	$ 5,131

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued employee compensation	$ 5,984	$ 3,135
Accrued research and development costs	1,844	1,115
Accrued professional services	856	1,391
Other	812	576
Total accrued liabilities	$ 9,496	$ 6,217

Commitments and Contingencies - Additional Information (Details)	1 Months Ended			3 Months Ended		9 Months Ended
	Feb. 28, 2019	Oct. 31, 2018	May 31, 2018 ft²	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset				$ 2,155,000		$ 2,155,000
Operating lease liability				2,285,000		2,285,000
Rent expense				300,000	$ 200,000	$ 900,000	$ 500,000
Fremont, California
Loss Contingencies [Line Items]
Lease term expiration date	Sep. 30, 2019	Jun. 30, 2019				Sep. 30, 2019
Santa Clara, California
Loss Contingencies [Line Items]
Lease term expiration date			Aug. 31, 2022
Lease commencement date			2018-09
Area of office and laboratory space \| ft²			35,000
Letter of credit secured by restricted cash				500,000		$ 500,000
Operating lease right-of-use asset				2,200,000		2,200,000
Operating lease liability				2,200,000		$ 2,200,000
Operating lease, remaining lease term						2 years 10 months
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset				47,000		$ 47,000
Operating lease liability				$ 47,000		$ 47,000
Operating lease, weighted average remaining lease term				8 months		8 months
Operating lease liability, weighted average incremental borrowing rate						6.93%

Commitments and Contingencies - Schedule of Carrying Value of Operating Lease Liabilities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2019	$ 222
2020	861
2021	855
2022	581
Total minimum lease payments	2,519
Less: imputed interest	(234)
Total lease liability	$ 2,285

Convertible Preferred Stock and Stockholder's Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 11, 2019	Mar. 06, 2019	Mar. 05, 2019	Apr. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Temporary Equity And Stockholders Equity [Line Items]
Preferred stock, shares authorized							5,000,000
Preferred stock, shares issued							0
Preferred stock, shares outstanding							0
Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Warrants exercised price								$ 2.196
Initial Public Offering \| Common Stock Warrants Related to Convertible Preferred Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants issued		54,903
Adjustments to additional paid in capital		$ 0.8
Issuance of common stock upon net exercise of warrants, shares				49,321
Initial Public Offering \| Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants exercised		91,446
Warrants exercised price		$ 17.00
Common stock issued upon exercise of common stock warrants		79,632
Convertible Preferred Stock
Temporary Equity And Stockholders Equity [Line Items]
Convertible preferred stock, shares outstanding			18,670,259					18,670,328	17,579,720	17,579,720	17,562,214	17,510,045
Fractional shares issued in reverse stock split							69
Common Stock
Temporary Equity And Stockholders Equity [Line Items]
Conversion of stock, common stock issued			18,670,259
Fractional shares issued in reverse stock split							45	45
Issuance of common stock upon net exercise of warrants, shares	101,744			29,887	79,208	101,744

Convertible Preferred Stock and Stockholder's Equity (Deficit) - Summary of Key Terms of Outstanding Common Stock Warrants (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	176,218
Related Party Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	141,778
Warrants Outstanding Exercise Price \| $ / shares	$ 2.196
Warrants Outstanding Expiration	2025-05
Common Stock Warrants Related to 2018 Loan and Security Agreement
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	34,440
Warrants Outstanding Exercise Price \| $ / shares	$ 4.026
Warrants Outstanding Expiration	2028-02

Stock-Based Compensation - Schedule of Total Stock-Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,106	$ 289	$ 2,336	$ 874
Cost of Product Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	81	7	156	38
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	307	47	582	146
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	288	66	597	185
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 430	$ 169	$ 1,001	$ 505

Stock-Based Compensation - Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions (Detail)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)	6 years 29 days	6 years 29 days
Expected volatility, minimum	42.40%	40.80%
Expected volatility, maximum	42.90%	45.90%
Risk-free interest rate, minimum	2.40%	1.90%
Risk-free interest rate, maximum	2.60%	2.90%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended
	Mar. 31, 2019	Feb. 28, 2019	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation				$ 2,336,000	$ 874,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period				4 years
Cliff vesting, percentage				25.00%
Share-based compensation vesting rights, terms				The RSUs generally vest over a four-year period with straight-line vesting and a 25% one year cliff or over a three year period in equal amounts on a semi-annual basis,
2019 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		2,000,430
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%
Shares available for issuance			1,470,192	1,470,192
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance			300,650	300,650
Purchase shares of common stock, price per share, percentage of fair market value	85.00%
Stock-based compensation			$ 64,000	$ 64,000

Stock-Based Compensation - Schedule of Option Activity under 2009 Plan and 2019 Plan (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Number of Shares
Number of Shares, Beginning balance \| shares	3,636,358
Number of Shares, Options granted \| shares	442,858
Number of Shares, Options exercised \| shares	(386,309)
Number of Shares, Options forfeited \| shares	(34,471)
Number of Shares, Ending balance \| shares	3,658,436	3,636,358
Number of Shares, Vested and exercisable, September 30, 2019 \| shares	1,831,368
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance \| $ / shares	$ 3.54
Weighted-Average Exercise Price Per Share, Options granted \| $ / shares	14.69
Weighted-Average Exercise Price Per Share, Options exercised \| $ / shares	2.65
Weighted-Average Exercise Price Per Share, Options forfeited \| $ / shares	3.49
Weighted-Average Exercise Price Per Share, Ending balance \| $ / shares	4.95	$ 3.54
Weighted-Average Exercise Price Per Share, Vested and exercisable, September 30, 2019 \| $ / shares	$ 3.14
Weighted-Average Remaining Term
Weighted-Average Remaining Term, Balance	7 years 6 months 7 days	7 years 9 months 14 days
Weighted-Average Remaining Term, Vested and exercisable, September 30, 2019	6 years 7 months 2 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Balance \| $	$ 91,399	$ 11,267
Aggregate Intrinsic Value, Vested and exercisable, September 30, 2019 \| $	$ 49,068

Stock-Based Compensation - Schedule of RSU Activity under 2019 Plan (Detail) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Number of Shares
Number of Shares, RSUs granted \| shares	229,450
Number of Shares, RSUs forfeited \| shares	(2,900)
Number of Shares, Ending balance \| shares	226,550
Weighted-Average Grant Date Fair Value Per Share
Weighted-Average Grant Date Fair Value Per Share, RSUs granted \| $ / shares	$ 38.26
Weighted-Average Grant Date Fair Value Per Share, RSUs forfeited \| $ / shares	37.51
Weighted-Average Grant Date Fair Value Per Share, Ending balance \| $ / shares	$ 38.27

Net Loss Per Share - Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,884,986	21,145,718
Convertible Preferred Stock on an As-Converted Basis
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		17,579,720
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	3,658,436	3,313,257
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	226,550
Early Exercised Options Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		21,620
Convertible Preferred Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		54,903
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		176,218

Segment and Geographic Information - Schedule of Product Revenue Based on Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 11,333	$ 3,600	$ 28,615	$ 7,201
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 6,246	$ 2,053	$ 15,054	$ 4,476
Germany
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	873	439	2,389	958
Rest of Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	3,428	995	9,473	1,597
All Other Countries
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 786	$ 113	$ 1,699	$ 170