Silk Road Medical (SILK) 10-Q 10 May 22 2022 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2022	Apr. 30, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38847
Entity Registrant Name	SILK ROAD MEDICAL, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8777622
Entity Address, Address Line One	1213 Innsbruck Dr.
Entity Address, City or Town	Sunnyvale
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94089
City Area Code	408
Local Phone Number	720-9002
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Trading Symbol	SILK
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		35,116,361
Entity Central Index Key	0001397702
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false

Condensed Balance Sheets

Condensed Balance Sheets - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 93,602,000	$ 110,231,000
Short-term investments	0	0
Accounts receivable, net	13,876,000	11,832,000
Inventories	17,726,000	17,851,000
Prepaid expenses and other current assets	2,564,000	3,412,000
Total current assets	127,768,000	143,326,000
Property and equipment, net	9,866,000	7,697,000
Restricted cash	232,000	232,000
Other non-current assets	5,134,000	5,370,000
Total assets	143,000,000	156,625,000
Current liabilities:
Accounts payable	2,926,000	2,379,000
Accrued liabilities	16,744,000	19,802,000
Short-term debt	9,829,000	3,905,000
Total current liabilities	29,499,000	26,086,000
Long-term debt	38,901,000	44,786,000
Other liabilities	6,893,000	6,513,000
Total liabilities	75,293,000	77,385,000
Commitments and contingencies (Note 7)
Stockholders’ equity):
Preferred stock, $0.001 par value Shares authorized: 5,000,000 at March 31, 2022 and December 31, 2021 Shares issued and outstanding: none at March 31, 2022 and December 31, 2021
Common stock, $0.001 par value Shares authorized: 100,000,000 at March 31, 2022 and December 31, 2021 Shares issued and outstanding: 35,073,602 and 34,980,896 at March 31, 2022 and December 31, 2021, respectively	35,000	35,000
Additional paid-in capital	373,053,000	367,907,000
Accumulated deficit	(305,381,000)	(288,702,000)
Total stockholders’ equity	67,707,000	79,240,000
Total liabilities and stockholders’ equity	$ 143,000,000	$ 156,625,000

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Preferred stock, $0.001 par value
Preferred shares (in USD per share)	$ 0.001	$ 0.001
Preferred shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, $0.001 par value
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	35,073,602	34,980,896
Shares outstanding (in shares)	35,073,602	34,980,896

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Condensed Statements of Operations and Comprehensive Loss [Abstract]
Revenue	$ 28,021	$ 22,053
Cost of goods sold	8,577	5,538
Gross profit	19,444	16,515
Operating expenses:
Research and development	8,123	5,484
Selling, general and administrative	27,275	21,194
Total operating expenses	35,398	26,678
Loss from operations	(15,954)	(10,163)
Interest income	12	95
Interest expense	(621)	(623)
Other income (expense), net	(116)	(3)
Net loss	(16,679)	(10,694)
Other comprehensive loss:
Change in unrealized gain (loss) on investments, net		(33)
Net change in other comprehensive loss		(33)
Net loss and comprehensive loss	$ (16,679)	$ (10,727)
Net loss per share, basic and diluted	$ (0.48)	$ (0.31)
Weighted average common shares used to compute net loss per share, basic and diluted	35,023,297	34,336,433

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Total
Beginning balance (in shares) at Dec. 31, 2020	34,249,649
Beginning balance at Dec. 31, 2020	$ 34	$ 346,318	$ (238,891)	$ 39	$ 107,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options		848			848
Exercise of stock options (in shares)	163,151
Issuance of common stock upon release of restricted stock units (in shares)	25,490
Stock-based compensation		3,533			3,533
Net loss			(10,694)		(10,694)
Unrealized loss on investments, net				(33)	(33)
Ending balance (in shares) at Mar. 31, 2021	34,438,290
Ending balance at Mar. 31, 2021	$ 34	350,699	(249,585)	$ 6	101,154
Beginning balance (in shares) at Dec. 31, 2021	34,980,896
Beginning balance at Dec. 31, 2021	$ 35	367,907	(288,702)		79,240
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options		168			$ 168
Exercise of stock options (in shares)	35,453				35,453
Issuance of common stock upon release of restricted stock units (in shares)	57,253
Stock-based compensation		4,978			$ 4,978
Net loss			(16,679)		(16,679)
Ending balance (in shares) at Mar. 31, 2022	35,073,602
Ending balance at Mar. 31, 2022	$ 35	$ 373,053	$ (305,381)		$ 67,707

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (16,679)	$ (10,694)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	420	239
Stock-based compensation expense	4,978	3,533
Amortization of premiums on investments, net		186
Amortization of debt discount and debt issuance costs	39	41
Amortization of right-of-use asset	242	158
Loss on disposal of property and equipment	120
Change in provision for doubtful accounts receivable	(6)
Provision for excess and obsolete inventories	(8)	24
Changes in assets and liabilities:
Accounts receivable	(2,038)	(2,036)
Inventories	134	(1,790)
Prepaid expenses and other current assets	847	583
Other assets	(5)	(6)
Accounts payable	19	218
Accrued liabilities	(3,168)	(2,423)
Other liabilities	380	(5)
Net cash used in operating activities	(14,725)	(11,972)
Cash flows from investing activities
Purchases of property and equipment	(2,072)	(67)
Proceeds from maturity of investments		36,300
Net cash provided by (used in) investing activities	(2,072)	36,233
Cash flows from financing activities
Proceeds from issuance of common stock	168	848
Net cash provided by financing activities	168	848
Net change in cash, cash equivalents and restricted cash	(16,629)	25,109
Cash, cash equivalents and restricted cash, beginning of period	110,463	69,776
Cash, cash equivalents and restricted cash, end of period	93,834	94,885
Supplemental disclosure of cash flow information
Cash paid for interest	582	582
Noncash investing and financing activities:
Accounts payable and accrued liabilities for purchases of property and equipment	$ 638	$ 106

Formation and Business of the C

Formation and Business of the Company	3 Months Ended
	Mar. 31, 2022
Balance Sheet Components [Abstract]
Formation and Business of the Company	1. Formation and Business of the Company The Company Silk Road Medical, Inc. (the “Company”) was incorporated in the state of Delaware on March 21, 2007. The Company has developed a technologically advanced, minimally-invasive solution for patients with carotid artery disease who are at risk for stroke. The Company's portfolio of TCAR products enable a new procedure, referred to as transcarotid artery revascularization, or TCAR, that combines the benefits of endovascular techniques and surgical principles. The Company manufactures and sells in the United States its portfolio of TCAR products which are designed to provide direct access to the carotid artery, effective reduction in stroke risk throughout the procedure, and long-term restraint of carotid plaque. The Company commercialized its products in the United States in late 2015.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Preparation The accompanying financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2021, and related disclosures, have been derived from the audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These unaudited condensed financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s condensed financial information. The results of operations for the three months ended March 31, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other interim period or for any other future year. The accompanying interim unaudited condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2021 included in the Company's annual report on Form 10-K filed with the SEC on March 1, 2022. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. Management uses judgment when making estimates related to provisions for accounts receivable and excess and obsolete inventories, the valuation of deferred tax assets, the reserves for sales returns, and stock-based compensation. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately differ from these estimates and assumptions. Due to the coronavirus (“COVID-19”) pandemic, there has been continued uncertainty and disruption in the global economy, supply chain, financial markets and increased labor shortages. New virus variants and increased infection rates continue to make the current COVID-related environment highly volatile and uncertain. These challenges continued to impact the number of TCAR procedures in 2021 and the first quarter of 2022, with procedure volumes impacted by increased COVID-19 hospitalizations and hospital capacity constraints due to COVID-19 and its variants . The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of March 31, 2022. The Company has also considered information available to it as of the date of issuance of these financial statements and is not aware of any specific events or circumstances that would require an update to its estimates or judgments, or a revision to the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information becomes available. Actual results could differ materially from these estimates. Fair Value of Financial Instruments The Company has evaluated the estimated fair value of its financial instruments as of March 31, 2022 and December 31, 2021. The carrying amounts of certain of the Company’s financial instruments, which include cash equivalents, restricted cash, accounts receivable, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these instruments. Management believes that its debt bears interest at the prevailing market rates for instruments with similar characteristics (Level 2 within the fair value hierarchy); accordingly, the carrying value of this instrument approximates its fair value. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are recorded at fair value, based on quoted market prices. As of March 31, 2022 and December 31, 2021, the Company’s cash equivalents are entirely comprised of investments in money market funds. Restricted cash as of March 31, 2022 and December 31, 2021 consists of a letter of credit of $ 232,000 representing collateral for the Company's facility lease in California. Investments Short-term investments consist of debt securities classified as available-for-sale and have original maturities greater than 90 days, but less than one year as of the balance sheet date. Long-term investments have maturities greater than one year as of the balance sheet date. All investments are recorded at fair value based on the fair value hierarchy. Money market funds are classified within Level 1 of the fair value hierarchy, and commercial paper, corporate bonds/notes, United States Government securities, and asset-backed securities are classified within Level 2 of the fair value hierarchy. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). Realized gains and losses are included in earnings and are der ived based on the specific-identification method for determining the costs of investments sold and were insignificant for the three months ended March 31, 2022 and 2021. Amortization of premiums and accretion of discounts are reported as a component of interest income. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the investment. The Company evaluates the securities in an unrealized loss position for expected credit losses by considering factors such as historical experience, market data, issuer-specific factors, current economic conditions and credit ratings. Concentration of Credit Risk, and Other Risks and Uncertainties The Company is subject to risks related to public health crises such as the global pandemic associated with COVID-19. The COVID-19 outbreak has negatively impacted, and may continue to negatively impact the Company’s operations, its revenue and overall financial condition by significantly decreasing the number of TCAR procedures performed. The number of TCAR procedures performed, similar to other surgical procedures, has significantly decreased as health care organizations globally prioritized the treatment of patients with COVID-19. In the past governmental authorities have recommended, and in certain cases required, that elective, specialty and other procedures and appointments, be suspended or canceled to focus limited resources and personnel and hospital capacity toward the treatment of COVID-19 and to avoid exposing patients to COVID-19. These measures and challenges will likely continue for the duration of the pandemic, which is uncertain, and will continue to negatively impact the Company’s revenue while the pandemic continues. New virus variants, and increased infection rates continue to make the current COVID-related environment highly volatile and uncertain. Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents and accounts receivable to the extent of the amounts recorded on the balance sheet. Cash, cash equivalents, and investments are deposited in financial institutions which, at times, may be in excess of federally insured limits. Cash equivalents are invested in highly rated money market funds. The Company invests in a variety of financial instruments, such as, but not limited to, commercial paper, corporate bonds/notes, United States Government securities, asset-backed securities and, by policy, limits the amount of credit exposure with any one financial institution or commercial issuer. The Company has not experienced any material losses on its deposits of cash and cash equivalents or investments during the three months ended March 31, 2022 and 2021. The Company’s accounts receivable are due from a variety of health care organizations in the United States. At March 31, 2022 and December 31, 2021, no customer represented 10% or more of the Company’s accounts receivable. For the three months ended March 31, 2022 and 2021, there were no customers that represented 10% or more of revenue. The Company provides for uncollectible amounts when specific credit problems are identified. In doing so, the Company analyzes historical bad debt trends, customer credit worthiness, current economic trends and changes in customer payment patterns when evaluating the adequacy of the allowance for expected credit losses on customer accounts. The Company manufactures certain of its commercial products in-house. Certain of the Company’s product components and sub-assemblies continue to be manufactured by sole suppliers, the most significant of which is the ENROUTE Transcarotid Stent System, manufactured by Cordis Corporation, or Cordis. Disruption in component or sub-assembly supply from these manufacturers or from in-house production would have a negative impact on the Company’s financial position and results of operations. The Company is subject to certain risks, including that its devices may not be approved or cleared for marketing by governmental authorities or be successfully marketed. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence upon government and third-party payers to provide adequate coverage and reimbursement, dependence on key personnel and suppliers, protection of proprietary technology, product liability claims, and compliance with government regulations. Existing or future devices developed by the Company may require approvals or clearances from the FDA or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If the Company were denied or delayed in receiving such approvals or clearances, it may be necessary to adjust operations to align with the Company’s currently approved portfolio. If clearance for the products in the current portfolio were withdrawn by the FDA, this would have a material adverse impact on the Company. Voluntary Recall In January and February 2021, the Company announced the voluntary recall of certain lots of its ENROUTE Transcarotid Stent System, manufactured by one of its third-party suppliers, Cordis. The decision to recall these lots was based on complaints received about tips detaching from the stent delivery system as well as internal testing that the Company conducted. The Company believes the root cause of the detachment was a single operator at Cordis, who, over a specific timeframe, produced lots in which a small number of units were not reliably manufactured to specification. As a result of the voluntary recall the Company reflected a current asset of $ 335,000 on its balance sheet as of December 31, 2021, relating to other direct costs that remain to be reimbursed by Cordis, which was fully paid as of March 31, 2022. In addition, as of March 31, 2022 and December 31, 2021, the Company has a remaining accrual of $ 11,000 relating to its obligation to provide replacement ENROUTE stent delivery systems to its customers. Leases The Company accounts for its leasing arrangements in accordance with Accounting Standards Codification (“ASC”) 842, “Leases.” The Company considers if an arrangement is a lease at inception if it obtains the right to control the use of an identified asset under a leasing arrangement with an initial term greater than twelve months. The Company determines whether a contract conveys the right to control the use of an identified asset for a period of time if the contract contains both the right to obtain substantially all of the economic benefits from the use of the identified asset and the right to direct the use of the identified asset. The Company also evaluates the nature of each lease to determine whether it is an operating or financing lease and recognizes the right-of-use asset and lease liabilities based on the present value of future minimum lease payments over the expected lease term. The Company’s leases do not generally contain an implicit interest rate and therefore the Company uses the incremental borrowing rate it would expect to pay to borrow on a similar collateralized basis over a similar term in order to determine the present value of its lease payments. The Company considers renewal options in the determination of the lease term if the option to renew is reasonably certain. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease costs, which consists primarily of taxes, insurance and common area maintenance costs, are expensed as incurred. The Company elected to account for contracts that contain lease and non-lease components as a single component, consistent with its historical practice. The Company does not have any finance leases. Reven ue Recognition The Company recognizes revenue in accordance with ASC Topic 606, "Revenue from Contracts with Customers." Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services, in an amou nt 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. As of March 31, 2022 and December 31, 2021, the Company recorded $ 255,000 and $ 87,000 , respectively, of unbilled receivables, which are included in accounts receivable, net on the condensed balance sheet, as the Company has an unconditional right to payment as of the end of the applicable period. The Company’s revenue is generated from the sale of its products to hospitals and medical centers in the United States through direct sales representatives. Revenue is recognized when obligations under the terms of a contract with customers are satisfied, which occurs with the transfer of control of the Company’s products to its customers, either upon shipment of the product or delivery of the product to the customer under the Company’s standard terms and conditions. The Company’s products are readily available for usage as soon as the customer possesses it. Upon receipt, the customer controls the economic benefits of the product, has significant risks and rewards, and the legal title. The Company has present right to payment; therefore, the transfer of control is deemed to happen at a point in time. Revenue is measured as the amount of consideration the Company expects to receive in exchange for transferring the goods. For sales where the Company’s sales representative hand delivers product directly to the hospital or medical center from the sales representative’s trunk stock inventory, the Company recognizes revenue upon delivery, which represents the point in time when control transfers to the customer. Upon delivery there are legally-enforceable rights and obligations between the parties which can be identified, commercial substance exists and collectability is probable. For sales which are sent directly from the Company to hospitals and medical centers, the transfer of control occurs at the time of shipment or delivery of the product. There are no further performance obligations by the Company or the sales representative to the customer after delivery under either method of sale. As allowed under the practical expedient, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. The Company is entitled to the total consideration for the products ordered by customers as product pricing is fixed according to the terms of customer contracts and payment terms are short. Payment terms fall within the one-year guidance for the practical expedient which allows the Company to forgo adjustment of the promised amount of consideration for the effects of a significant financing component. The Company excludes taxes assessed by governmental authorities on revenue-producing transactions from the measurement of the transaction price. Costs associated with product sales include commissions and royalties. The Company applies the practical expedient and recognizes commissions and royalties as expense when incurred because the expense is incurred at a point in time and the amortization period is less than one year. Commissions are recorded as selling expense and royalties are recorded as cost of goods sold in the condensed statements of operations and comprehensive loss. The Company accepts product returns at its discretion or if the product is defective as manufactured. The Company establishes estimated provisions for returns based on historical experience and considers other factors that it believes could significantly impact its expected returns, which provisions are classified within accrued liabilities on the condensed balance sheet. The Company elected to expense shipping and handling costs as incurred and includes them in the cost of goods sold. In those cases where the Company bills shipping and handling costs to customers, it will classify the amounts billed as a component of revenue. Cost of Goods Sold The Company manufactures certain of its portfolio of TCAR products at its California facility and purchases other products from third party manufacturers. Cost of goods sold consists primarily of costs related to materials, components and sub-assemblies, manufacturing overhead costs, direct labor, reserves for excess, obsolete and non-sellable inventories as well as distribution-related expenses. A significant portion of the Company’s cost of goods sold currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment and operations supervision and management. Cost of goods sold also includes depreciation expense for production equipment and certain direct costs such as shipping costs and royalties. In May 2021, the Company entered into a lease for an additional facility in Minnesota and expects to begin commercial production in the second half of 2022. The Company is experiencing additional overhead expenses related to the start-up phase of its manufacturing capacity expansion, which were recorded as a period expense. Stock–Based Compensation The Company accounts for stock-based compensation in accordance with Financial Accounting Standards Board (“FASB”) ASC 718, "Compensation-Stock Compensation." ASC 718 requires the recognition of compensation expense, using a fair-value based method, for costs related to all share-based payments including stock options, restricted stock units and shares issued under its employee stock purchase plan. ASC 718 requires companies to estimate the fair value of all share-based payment option awards on the date of grant using an option pricing model. The fair value of stock options is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period), on a straight-line basis. For performance-based stock options, the Company will assess the probability of performance conditions being achieved in each reporting period. The amount of stock-based compensation expense recognized in any one period related to performance-based stock options can vary based on the achievement or anticipated achievement of the performance conditions. The Company accounts for option forfeitures as they occur. The Company accounts for stock-based compensation for restricted stock units at their fair value, based on the closing market price of the Company's common stock on the date of grant. These costs are recognized on a straight-line basis over the requisite service period, which is usually the vesting period. The Company accounts for stock-based compensation for its employee stock purchase plan based on the estimated fair value of the options on the date of grant. The Company estimates the grant date fair value using an option pricing model for each purchase period. These costs are recognized on a straight-line basis over the offering period. Income Taxes The Company accounts for income taxes under the liability method, whereby deferred tax assets and liabilities are determined based on the difference between the condensed financial statements and tax bases of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to affect taxable income. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. As the Company has historically incurred operating losses, it has established a full valuation allowance against its net deferred tax assets, and there is no provision for income taxes. The Company also follows the provisions of ASC 740-10, "A ccounting for Uncertainty in Income Taxes." ASC 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or expected to be taken on a tax return. No liability related to uncertain tax positions is recorded on the condensed financial statements. It is the Company's policy to include penalties and interest expense related to income taxes as part of the provision for income taxes. Comprehensive Loss Comprehensive loss consists of net loss and changes in unrealized gains and losses on investments classified as available-for-sale. For the three months ended March 31, 2022 and 2021 , the Company’s unrealized gains and losses on available-for-sale investments represent the only component of other comprehensive loss that are excluded from the reported net loss and that are presented in the condensed statements of operations and comprehensive loss. Accumulated other comprehensive loss is presented in the accompanying condensed balance sheets as a component of stockholders' equity. Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration for potential dilutive common shares. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, common stock options, and restricted stock units are considered to be potentially dilutive securities. Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share as the inclusion of all potential dilutive common shares would have been anti-dilutive. Net loss per share was determined as follows (in thousands, except share and per share data): Three Months Ended March 31, 2022 2021 Net loss $ ( 16,679 ) $ ( 10,694 ) Weighted average common stock outstanding used to compute net loss per share, basic and diluted 35,023,297 34,336,433 Net loss, basic and diluted $ ( 0.48 ) $ ( 0.31 ) The following potentially dilutive securities outstanding have been excluded from the computation of diluted weighted average shares outstanding because such securities have an antidilutive impact due to the Company's net loss: March 31, 2022 2021 Common stock options 4,197,518 4,288,835 Restricted stock units 1,123,515 251,138 5,321,033 4,539,973 Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Primarily all of the Company’s long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment. All of the Company’s revenue was in the United States for the three months ended March 31, 2022 and 2021, based on the shipping location of the external customer.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2022
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncements	3. Recent Accounting Pronouncements Recently Adopted Accounting Standards In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (“ASU 2021-08”), which creates an exception to the general recognition and measurement principle in ASC 805 by requiring companies to apply ASC 606 to recognize and measure contract assets and contract liabilities from contracts with customers acquired in a business combination. The guidance additionally clarifies that companies should apply the definition of a performance obligation in ASC 606 when recognizing contract liabilities assumed in a business combination. The Company early adopted ASU 2021-08 as of January 1, 2022, on a prospective basis. The adoption of ASU 2021-08 did not have a material impact on the Company’s financial statement and related disclosures.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Measurements [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: • Level 1 – quoted prices in active markets are identical assets and liabilities; • Level 2 – observable inputs other than quoted prices in active markets for identical assets and liabilities; • Level 3 – unobservable inputs. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The Company’s cash equivalents are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Any corporate bonds/notes, commercial paper, asset-backed securities and U.S. government securities are classified as Level 2 as they are valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. The following tables sets forth by level within the fair value hierarchy the Company’s assets that are reported at fair value as of March 31, 2022 and December 31, 2021, using the inputs defined above (in thousands): March 31, 2022 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 9,257 $ — $ — $ 9,257 $ 9,257 $ — $ — $ 9,257 December 31, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 21,062 $ — $ — $ 21,062 $ 21,062 $ — $ — $ 21,062 There were no transfers between fair value hierarchy levels during the three months ended March 31, 2022 and 2021.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2022
Balance Sheet Components [Abstract]
Balance Sheet Components	5. Balance Sheet Components Investments The Company’s cash equivalents consist of $ 9,257,000 and $ 21,062,000 in money market funds as of March 31, 2022 and December 31, 2021, respectively, and approximate fair value. The Company had no investments as of March 31, 2022 and December 31, 2021. All of the Company’s cash equivalents mature within one year as of March 31, 2022 and December 31, 2021. Inventories Components of inventories were as follows (in thousands): March 31, December 31, 2022 2021 Raw materials $ 3,031 $ 2,447 Finished products 14,708 15,437 17,739 17,884 Less: Reserve for excess and obsolete ( 13 ) ( 33 ) $ 17,726 $ 17,851 As of March 31, 2022 and December 31, 2021, there were no work-in-process inventories. Accrued Liabilities Accrued liabilities consist of the following (in thousands): March 31, December 31, 2022 2021 Accrued payroll and related expenses $ 9,889 $ 13,898 Provision for sales returns 481 359 Accrued professional services 2,290 2,039 Operating lease liability 1,519 1,294 Accrued royalty expense 682 687 Deferred revenue 522 157 Accrued travel expenses 637 590 Accrued clinical expenses 73 99 Accrued other expenses 651 679 Total $ 16,744 $ 19,802

Long-term Debt

Long-term Debt	3 Months Ended
	Mar. 31, 2022
Long-term Debt [Abstract]
Long-term Debt	6. Long-term Debt Stifel Bank In October 2020, the Company entered into a Loan and Security Agreement, or Loan Agreement, with Stifel Bank which provides for a $ 50,000,000 loan facility, comprised of a $ 50,000,000 secured revolving credit facility, with a $ 2,000,000 subfacility for the issuance of letters of credit and other ancillary banking services, and a $ 50,000,000 secured term loan facility, provided that amounts outstanding under both facilities may not exceed an aggregate principal amount of $ 50,000,000 at any time. Any borrowings under the revolving loan facility mature on October 29, 2022, or October 29, 2023 if as of October 29, 2022, no event of default has occurred and we are in compliance with the terms of the Loan Agreement. Borrowings under the term loan facility mature on October 29, 2024. Interest under the revolving credit facility is the greater of a) 0.5 % above the "Prime Rate" as published by The Wall Street Journal or b) 4.75 %. Also in October 2020, the Company drew down $ 49,000,000 under the term loan facility and used the majority of the proceeds to pay off and terminate the prior term loan agreement with CRG totaling $ 46,674,000 , which included a prepayment premium of $ 305,000 , a final interest payment of $ 365,000 and a facility fee of $ 2,191,000 . The Company recognized a loss on debt extinguishment of $ 1,119,000 in connection with the early termination of its prior term loan agreement with CRG. The principal amount of outstanding term loans under the Loan Agreement with Stifel Bank shall be repaid in equal monthly installments beginning on November 29, 2022. Interest under the term loan facility is the greater of a) 0.75 % above the "Prime Rate" as published by The Wall Street Journal or b) 4.75 %. The term loan may not be reborrowed once repaid, but the Company may prepay the term loan at any time without premium or penalty. The Company also concurrently entered in a Success Fee Agreement in October 2020 with Stifel Bank, which requires that the Company pay Stifel Bank the lesser of 0.75 % of the original principal amount of all credit extensions made under the Loan Agreement or $ 375,000 in the event the Company completes a Liquidity Event (liquidation, merger, sale of the Company or change in control). The Success Fee Agreement terminates on October 29, 2025. The Company has determined the probability of a Liquidity Event to be remote and accordingly, has not recognized a liability as of March 31, 2022. Obligations under the Loan Agreement are secured by substantially all of the Company's assets. The Loan Agreement requires that the Company maintain unrestricted cash and cash equivalents with Stifel Bank or at Stifel Bank Affiliates of at least $ 20,000,000 . In addition, for any fiscal quarter where the Company's unrestricted cash and cash equivalents maintained with Stifel Bank or at Stifel Bank Affiliates are less than $ 60,000,000 for any day during such fiscal quarter, the Company must comply with a minimum revenue covenant. Additionally, the Loan Agreement contains customary affirmative and negative covenants, including covenants limiting the Company's ability and the ability of the Company's subsidiaries to, among other things, dispose of assets, effect certain mergers, incur debt, grant liens, pay dividends and distributions on capital stock, make investments and acquisitions, and enter into transactions with affiliates, in each case subject to customary exceptions for a loan facility of this size and type. The events of default under the Loan Agreement include, among others, payment defaults, material misrepresentations, breaches of covenants, cross defaults with certain other material indebtedness, bankruptcy and insolvency events, and judgment defaults. The occurrence of an event of default could result in the acceleration of our obligations under the Loan Agreement, the termination of the lender’s commitments, a 5 % increase in the applicable rate of interest and the exercise by the lender of other rights and remedies provided for under the Loan Agreement. As of March 31, 2022, the aggregate outstanding principal balance under the Loan Agreement was $ 49,000,000 and the annual interest rate was 4.75 %. As of March 31, 2022, the Company was in compliance with all applicable financial covenants. As of March 31, 2022, management does not believe that it is probable that the above events of default will be triggered within the next twelve months, therefore, the debt is classified as short-term or long-term on the condensed balance sheet based on its future maturities. Future maturities under the Stifel Bank term loan agreement as of March 31, 2022 are as follows (in thousands): Period Ending December 31: Amount 2022 $ 5,675 2023 25,749 2024 21,457 52,881 Less: Amount representing interest ( 3,881 ) Less: Amount representing debt discount and debt issuance costs ( 270 ) Present value of minimum payments $ 48,730

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease and Rights-of-Use The Company’s operating lease obligation at its corporate headquarters in California consists of leased office, laboratory, and manufacturing space under a non-cancellable operating lease that expires in October 2024. The lease agreement includes a renewal provision allowing the Company to extend this lease for an additional period of five years . In May 2021, the Company entered into a new, non-cancelable operating lease for additional office, laboratory and manufacturing space in Minnesota that expires in November 2029. The lease agreement includes a renewal provision allowing the Company to extend this lease for two additional five year terms. In connection with the lease, the Company recognized a right-of-use asset and lease liability of $ 3,307,000 . Operating lease costs were $ 365,000 and $ 217,000 for the three months ended March 31, 2022 and 2021, respectively. Cash paid (net of tenant improvement allowances received) for amounts included in the measurement of operating lease liabilities was $( 704,000 ) and $ 203,000 for the three months ended March 31, 2022 and 2021, respectively. As of March 31, 2022, the weighted average discount rate was approximately 6.50 % and the weighted average remaining lease term was 5.94 years. Balance sheet information as of March 31, 2022 and December 31, 2021 consists of the following (in thousands): March 31, December 31, Operating Lease: 2022 2021 Operating lease right-of-use assets in other non-current assets $ 4,977 $ 5,219 Operating lease liabilities in accrued liabilities $ 1,519 $ 1,294 Operating lease liabilities in other liabilities 6,225 5,747 Total operating lease liabilities $ 7,744 $ 7,041 The following table summarizes the Company’s operating lease maturities as of March 31, 2022 (in thousands): Period Ending December 31: Amount 2022 $ 1,201 2023 1,967 2024 1,764 2025 882 2026 904 2027 and thereafter 2,769 Total lease payments $ 9,487 Less: interest ( 1,743 ) Total lease liabilities $ 7,744 Purchase Obligations Purchase obligations consist of agreements to purchase goods and services entered into in the ordinary course of business. As of March 31, 2022, the Company had non-cancellable purchase obligations to suppliers of $ 6,481,000 . Indemnification In the normal course of business, the Company enters into contracts and agreements with suppliers and other parties that contain a variety of representations and warranties and may provide for indemnification of the counterparty. The Company’s exposure under these agreements is unknown because it involves claims that may be made against it in the future but have not yet been made. To date, the Company has not been subject to any claims or been required to defend any action related to its indemnification obligations. The Company indemnifies each of its directors and officers for certain events or occurrences, subject to certain limits, while the director is or was serving at the Company’s request in such capacity, as permitted under Delaware law and in accordance with its certificate of incorporation and bylaws. The term of the indemnification period lasts as long as a director may be subject to any proceeding arising out of acts or omissions of such director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director liability insurance. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations as of March 31, 2022. Contingencies The Company is not involved in any pending legal proceedings that it believes could have a material adverse effect on its financial condition, results of operations or cash flows. From time to time, the Company may pursue litigation to assert its legal right and such litigation may be costly and divert the efforts and attention of its management and technical personnel which could adversely affect its business. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. There were no contingent liabilities requiring accrual at March 31, 2022 and December 31, 2021.

Stockholders_ Equity

Stockholders’ Equity	3 Months Ended
	Mar. 31, 2022
Stockholders’ Equity [Abstract]
Stockholders’ Equity	8. Stockholders’ Equity Preferred Stock At March 31, 2022, the Company’s certificate of incorporation, as amended and restated, authorizes the Company to issue up to 5,000,000 shares of preferred stock with $ 0.001 par value per share, of which no shares were issued and outstanding. Common Stock At March 31, 2022, the Company’s certificate of incorporation, as amended and restated, authorizes the Company to issue up to 100,000,000 shares of common stock with $ 0.001 par value per share, of which 35,073,602 shares were issued and outstanding. The holders of common stock are also entitled to receive dividends whenever funds are legally available, when and if declared by the Board of Directors. As of March 31, 2022, no dividends have been declared to date. Each share of common stock is entitled to one vote. Disgorgement Proceeds During the year ended December 31, 2021, the Company received net proceeds of $ 32,000 related to the disgorgement of short-swing profits under Section 16(b) of the Exchange Act. The amount was recorded as an increase to additional paid-in capital on the balance sheet.

Stock Option Plans

Stock Option Plans	3 Months Ended
	Mar. 31, 2022
Stock Option Plans [Abstract]
Stock Option Plans	9. Stock Option Plans As of March 31, 2022, the Company has reserved 6,416,747 shares of common stock for issuance under the 2019 Equity Incentive Plan, or the 2019 Plan. A summary of the shares available for issuance under the 2019 Plan is as follows: Number of Shares Balances, December 31, 2021 2,477,212 Authorized 1,399,235 Granted / Awarded ( 1,132,907 ) Cancelled 30,381 Balances, March 31, 2022 2,773,921 The exercise price of ISOs and NSOs shall not be less than 100 % and 85 %, respectively, of the estimated fair value of the shares on the date of grant as determined by the Board of Directors. The exercise price of ISOs and NSOs granted to a 10 % stockholder shall not be less than 110 % of the estimated fair value of the shares on the date of grant as determined by the Board of Directors. To date, options have a term of ten years and generally vest over 4 years from the date of grant. Stock option activity under the Company’s 2007 Stock Option Plan, 2015 Equity Incentive Plan and 2019 Plan is set forth below: Options Outstanding Number of Weighted Average Weighted Average Remaining Contractual Term Aggregate Intrinsic Shares Exercise Price (Years) Value Balances, December 31, 2021 3,780,939 $ 20.45 6.71 $ 91,900 Options granted 473,280 36.44 Options exercised ( 35,453 ) 4.74 Options cancelled ( 21,248 ) 40.47 Balances, March 31, 2022 4,197,518 $ 22.28 6.88 $ 88,620 Vested and exercisable at March 31, 2022 2,836,804 $ 14.53 6.00 $ 78,941 Vested and expected to vest at March 31, 2022 4,197,518 $ 22.28 6.88 $ 88,620 The aggregate intrinsic value of options exercised during the three months ended March 31, 2022 was $ 1,170,000 . The aggregate intrinsic value was calculated as the difference between the exercise prices of the underlying options and the estimated fair value of the common stock on the date of exercise. Restricted Stock Units In March 2020, the Company began granting restricted stock units, or RSUs, under the 2019 Plan. RSUs generally vest over four years in annual equal increments. The fair value of RSUs is based on the Company’s closing stock price on the date of grant. A summary of RSUs activity for the three months ended March 31, 2022 is as follows: Number of Restricted Stock Units Weighted Average Grant Date Fair Value Balances, December 31, 2021 530,274 $ 53.01 Awards granted 659,627 36.38 Awards vested ( 57,253 ) 49.86 Awards canceled ( 9,133 ) 47.83 Balances, March 31, 2022 1,123,515 $ 43.45 Expected to vest at March 31, 2022 1,123,515 $ 43.45 2019 Employee Stock Purchase Plan As of March 31, 2022, 166,951 shares of common stock have been issued to employees participating in the 2019 Employee Stock Purchase Plan, or the 2019 ESPP, and 1,271,905 shares were available for future issuance under the 2019 ESPP. Stock-Based Compensation The Company estimated the fair value of stock options using the Black–Scholes option pricing model. The fair value of employee and nonemployee stock options is being amortized on a straight–line basis over the requisite service period of the awards. The fair value of employee and nonemployee stock options was estimated using the following assumptions for the three months ended March 31, 2022 and 2021: Three Months Ended March 31, 2022 2021 Expected term (in years) 6.25 5.25 - 6.25 Expected volatility 48.2 % 45.0 % - 50.4 % Risk-free interest rate 1.60 % - 1.77 % 0.41 % - 0.98 % Dividend yield —% —% The fair value of the shares to be issued under the Company’s 2019 ESPP was estimated using the Black-Scholes valuation model with the following assumptions for the three months ended March 31, 2022 and 2021: Three Months Ended March 31, 2022 2021 Expected term (in years) 0.50 0.50 Expected volatility 51.6 % 46.9 % Risk-free interest rate 0.07 % 0.10 % Dividend yield —% —% The following table summarizes the total stock-based compensation expense included in the condensed statements of operations and comprehensive loss for all periods presented (in thousands): Three Months Ended March 31, 2022 2021 Cost of goods sold $ 221 $ 158 Research and development expenses 1,069 689 Selling, general and administrative expenses 3,688 2,686 $ 4,978 $ 3,533 As of March 31, 2022, there was total unrecognized compensation costs of $ 22,618,000 related to stock options expected to be recognized over a period of approximately 2.80 years, a total of $ 45,249,000 of unrecognized compensation costs related to unvested RSUs expected to be recognized over a period of approximately 3.52 years and $ 129,000 of unrecognized compensation costs related to the ESPP, which the Company will recognize over 0.13 years.

401(k) Plan

401(k) Plan	3 Months Ended
	Mar. 31, 2022
401(k) Plan [Abstract]
401(k) Plan	10. 401(k) Plan The Company has a qualified retirement plan under section 401(k) of the Internal Revenue Code (“IRC”) under which participants may contribute up to 90 % of their eligible compensation, subject to maximum deferral limits specified by the IRC. The Company may make a discretionary matching contribution to the 401(k) plan and may make a discretionary employer contribution to each eligible employee each year. Beginning in January 2020, the Company started matching employees' contributions to the 401(k) plan at 50 % of the first 5 % of compensation deferred to the 401(k) plan and at 50 % of the first 6 % of compensation deferred effective January 1, 2022. The Company's matching contributions were $ 589,000 and $ 366,000 for the three months ended March 31, 2022 and 2021.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Summary of Significant Accounting Policies [Abstract]
Basis of Preparation	Basis of Preparation The accompanying financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2021, and related disclosures, have been derived from the audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These unaudited condensed financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s condensed financial information. The results of operations for the three months ended March 31, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other interim period or for any other future year. The accompanying interim unaudited condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2021 included in the Company's annual report on Form 10-K filed with the SEC on March 1, 2022.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. Management uses judgment when making estimates related to provisions for accounts receivable and excess and obsolete inventories, the valuation of deferred tax assets, the reserves for sales returns, and stock-based compensation. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately differ from these estimates and assumptions. Due to the coronavirus (“COVID-19”) pandemic, there has been continued uncertainty and disruption in the global economy, supply chain, financial markets and increased labor shortages. New virus variants and increased infection rates continue to make the current COVID-related environment highly volatile and uncertain. These challenges continued to impact the number of TCAR procedures in 2021 and the first quarter of 2022, with procedure volumes impacted by increased COVID-19 hospitalizations and hospital capacity constraints due to COVID-19 and its variants . The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of March 31, 2022. The Company has also considered information available to it as of the date of issuance of these financial statements and is not aware of any specific events or circumstances that would require an update to its estimates or judgments, or a revision to the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information becomes available. Actual results could differ materially from these estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company has evaluated the estimated fair value of its financial instruments as of March 31, 2022 and December 31, 2021. The carrying amounts of certain of the Company’s financial instruments, which include cash equivalents, restricted cash, accounts receivable, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these instruments. Management believes that its debt bears interest at the prevailing market rates for instruments with similar characteristics (Level 2 within the fair value hierarchy); accordingly, the carrying value of this instrument approximates its fair value.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are recorded at fair value, based on quoted market prices. As of March 31, 2022 and December 31, 2021, the Company’s cash equivalents are entirely comprised of investments in money market funds. Restricted cash as of March 31, 2022 and December 31, 2021 consists of a letter of credit of $ 232,000 representing collateral for the Company's facility lease in California.
Investments	Investments Short-term investments consist of debt securities classified as available-for-sale and have original maturities greater than 90 days, but less than one year as of the balance sheet date. Long-term investments have maturities greater than one year as of the balance sheet date. All investments are recorded at fair value based on the fair value hierarchy. Money market funds are classified within Level 1 of the fair value hierarchy, and commercial paper, corporate bonds/notes, United States Government securities, and asset-backed securities are classified within Level 2 of the fair value hierarchy. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). Realized gains and losses are included in earnings and are der ived based on the specific-identification method for determining the costs of investments sold and were insignificant for the three months ended March 31, 2022 and 2021. Amortization of premiums and accretion of discounts are reported as a component of interest income. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the investment. The Company evaluates the securities in an unrealized loss position for expected credit losses by considering factors such as historical experience, market data, issuer-specific factors, current economic conditions and credit ratings.
Concentration of Credit Risk, and Other Risks and Uncertainties	Concentration of Credit Risk, and Other Risks and Uncertainties The Company is subject to risks related to public health crises such as the global pandemic associated with COVID-19. The COVID-19 outbreak has negatively impacted, and may continue to negatively impact the Company’s operations, its revenue and overall financial condition by significantly decreasing the number of TCAR procedures performed. The number of TCAR procedures performed, similar to other surgical procedures, has significantly decreased as health care organizations globally prioritized the treatment of patients with COVID-19. In the past governmental authorities have recommended, and in certain cases required, that elective, specialty and other procedures and appointments, be suspended or canceled to focus limited resources and personnel and hospital capacity toward the treatment of COVID-19 and to avoid exposing patients to COVID-19. These measures and challenges will likely continue for the duration of the pandemic, which is uncertain, and will continue to negatively impact the Company’s revenue while the pandemic continues. New virus variants, and increased infection rates continue to make the current COVID-related environment highly volatile and uncertain. Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents and accounts receivable to the extent of the amounts recorded on the balance sheet. Cash, cash equivalents, and investments are deposited in financial institutions which, at times, may be in excess of federally insured limits. Cash equivalents are invested in highly rated money market funds. The Company invests in a variety of financial instruments, such as, but not limited to, commercial paper, corporate bonds/notes, United States Government securities, asset-backed securities and, by policy, limits the amount of credit exposure with any one financial institution or commercial issuer. The Company has not experienced any material losses on its deposits of cash and cash equivalents or investments during the three months ended March 31, 2022 and 2021. The Company’s accounts receivable are due from a variety of health care organizations in the United States. At March 31, 2022 and December 31, 2021, no customer represented 10% or more of the Company’s accounts receivable. For the three months ended March 31, 2022 and 2021, there were no customers that represented 10% or more of revenue. The Company provides for uncollectible amounts when specific credit problems are identified. In doing so, the Company analyzes historical bad debt trends, customer credit worthiness, current economic trends and changes in customer payment patterns when evaluating the adequacy of the allowance for expected credit losses on customer accounts. The Company manufactures certain of its commercial products in-house. Certain of the Company’s product components and sub-assemblies continue to be manufactured by sole suppliers, the most significant of which is the ENROUTE Transcarotid Stent System, manufactured by Cordis Corporation, or Cordis. Disruption in component or sub-assembly supply from these manufacturers or from in-house production would have a negative impact on the Company’s financial position and results of operations. The Company is subject to certain risks, including that its devices may not be approved or cleared for marketing by governmental authorities or be successfully marketed. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence upon government and third-party payers to provide adequate coverage and reimbursement, dependence on key personnel and suppliers, protection of proprietary technology, product liability claims, and compliance with government regulations. Existing or future devices developed by the Company may require approvals or clearances from the FDA or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If the Company were denied or delayed in receiving such approvals or clearances, it may be necessary to adjust operations to align with the Company’s currently approved portfolio. If clearance for the products in the current portfolio were withdrawn by the FDA, this would have a material adverse impact on the Company.
Voluntary Recall	Voluntary Recall In January and February 2021, the Company announced the voluntary recall of certain lots of its ENROUTE Transcarotid Stent System, manufactured by one of its third-party suppliers, Cordis. The decision to recall these lots was based on complaints received about tips detaching from the stent delivery system as well as internal testing that the Company conducted. The Company believes the root cause of the detachment was a single operator at Cordis, who, over a specific timeframe, produced lots in which a small number of units were not reliably manufactured to specification. As a result of the voluntary recall the Company reflected a current asset of $ 335,000 on its balance sheet as of December 31, 2021, relating to other direct costs that remain to be reimbursed by Cordis, which was fully paid as of March 31, 2022. In addition, as of March 31, 2022 and December 31, 2021, the Company has a remaining accrual of $ 11,000 relating to its obligation to provide replacement ENROUTE stent delivery systems to its customers.
Leases	Leases The Company accounts for its leasing arrangements in accordance with Accounting Standards Codification (“ASC”) 842, “Leases.” The Company considers if an arrangement is a lease at inception if it obtains the right to control the use of an identified asset under a leasing arrangement with an initial term greater than twelve months. The Company determines whether a contract conveys the right to control the use of an identified asset for a period of time if the contract contains both the right to obtain substantially all of the economic benefits from the use of the identified asset and the right to direct the use of the identified asset. The Company also evaluates the nature of each lease to determine whether it is an operating or financing lease and recognizes the right-of-use asset and lease liabilities based on the present value of future minimum lease payments over the expected lease term. The Company’s leases do not generally contain an implicit interest rate and therefore the Company uses the incremental borrowing rate it would expect to pay to borrow on a similar collateralized basis over a similar term in order to determine the present value of its lease payments. The Company considers renewal options in the determination of the lease term if the option to renew is reasonably certain. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease costs, which consists primarily of taxes, insurance and common area maintenance costs, are expensed as incurred. The Company elected to account for contracts that contain lease and non-lease components as a single component, consistent with its historical practice. The Company does not have any finance leases.
Revenue Recognition and Cost of Goods Sold	Reven ue Recognition The Company recognizes revenue in accordance with ASC Topic 606, "Revenue from Contracts with Customers." Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services, in an amou nt 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. As of March 31, 2022 and December 31, 2021, the Company recorded $ 255,000 and $ 87,000 , respectively, of unbilled receivables, which are included in accounts receivable, net on the condensed balance sheet, as the Company has an unconditional right to payment as of the end of the applicable period. The Company’s revenue is generated from the sale of its products to hospitals and medical centers in the United States through direct sales representatives. Revenue is recognized when obligations under the terms of a contract with customers are satisfied, which occurs with the transfer of control of the Company’s products to its customers, either upon shipment of the product or delivery of the product to the customer under the Company’s standard terms and conditions. The Company’s products are readily available for usage as soon as the customer possesses it. Upon receipt, the customer controls the economic benefits of the product, has significant risks and rewards, and the legal title. The Company has present right to payment; therefore, the transfer of control is deemed to happen at a point in time. Revenue is measured as the amount of consideration the Company expects to receive in exchange for transferring the goods. For sales where the Company’s sales representative hand delivers product directly to the hospital or medical center from the sales representative’s trunk stock inventory, the Company recognizes revenue upon delivery, which represents the point in time when control transfers to the customer. Upon delivery there are legally-enforceable rights and obligations between the parties which can be identified, commercial substance exists and collectability is probable. For sales which are sent directly from the Company to hospitals and medical centers, the transfer of control occurs at the time of shipment or delivery of the product. There are no further performance obligations by the Company or the sales representative to the customer after delivery under either method of sale. As allowed under the practical expedient, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. The Company is entitled to the total consideration for the products ordered by customers as product pricing is fixed according to the terms of customer contracts and payment terms are short. Payment terms fall within the one-year guidance for the practical expedient which allows the Company to forgo adjustment of the promised amount of consideration for the effects of a significant financing component. The Company excludes taxes assessed by governmental authorities on revenue-producing transactions from the measurement of the transaction price. Costs associated with product sales include commissions and royalties. The Company applies the practical expedient and recognizes commissions and royalties as expense when incurred because the expense is incurred at a point in time and the amortization period is less than one year. Commissions are recorded as selling expense and royalties are recorded as cost of goods sold in the condensed statements of operations and comprehensive loss. The Company accepts product returns at its discretion or if the product is defective as manufactured. The Company establishes estimated provisions for returns based on historical experience and considers other factors that it believes could significantly impact its expected returns, which provisions are classified within accrued liabilities on the condensed balance sheet. The Company elected to expense shipping and handling costs as incurred and includes them in the cost of goods sold. In those cases where the Company bills shipping and handling costs to customers, it will classify the amounts billed as a component of revenue. Cost of Goods Sold The Company manufactures certain of its portfolio of TCAR products at its California facility and purchases other products from third party manufacturers. Cost of goods sold consists primarily of costs related to materials, components and sub-assemblies, manufacturing overhead costs, direct labor, reserves for excess, obsolete and non-sellable inventories as well as distribution-related expenses. A significant portion of the Company’s cost of goods sold currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment and operations supervision and management. Cost of goods sold also includes depreciation expense for production equipment and certain direct costs such as shipping costs and royalties. In May 2021, the Company entered into a lease for an additional facility in Minnesota and expects to begin commercial production in the second half of 2022. The Company is experiencing additional overhead expenses related to the start-up phase of its manufacturing capacity expansion, which were recorded as a period expense.
Stock-Based Compensation	Stock–Based Compensation The Company accounts for stock-based compensation in accordance with Financial Accounting Standards Board (“FASB”) ASC 718, "Compensation-Stock Compensation." ASC 718 requires the recognition of compensation expense, using a fair-value based method, for costs related to all share-based payments including stock options, restricted stock units and shares issued under its employee stock purchase plan. ASC 718 requires companies to estimate the fair value of all share-based payment option awards on the date of grant using an option pricing model. The fair value of stock options is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period), on a straight-line basis. For performance-based stock options, the Company will assess the probability of performance conditions being achieved in each reporting period. The amount of stock-based compensation expense recognized in any one period related to performance-based stock options can vary based on the achievement or anticipated achievement of the performance conditions. The Company accounts for option forfeitures as they occur. The Company accounts for stock-based compensation for restricted stock units at their fair value, based on the closing market price of the Company's common stock on the date of grant. These costs are recognized on a straight-line basis over the requisite service period, which is usually the vesting period. The Company accounts for stock-based compensation for its employee stock purchase plan based on the estimated fair value of the options on the date of grant. The Company estimates the grant date fair value using an option pricing model for each purchase period. These costs are recognized on a straight-line basis over the offering period.
Income Taxes	Income Taxes The Company accounts for income taxes under the liability method, whereby deferred tax assets and liabilities are determined based on the difference between the condensed financial statements and tax bases of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to affect taxable income. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. As the Company has historically incurred operating losses, it has established a full valuation allowance against its net deferred tax assets, and there is no provision for income taxes. The Company also follows the provisions of ASC 740-10, "A ccounting for Uncertainty in Income Taxes." ASC 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or expected to be taken on a tax return. No liability related to uncertain tax positions is recorded on the condensed financial statements. It is the Company's policy to include penalties and interest expense related to income taxes as part of the provision for income taxes.
Comprehensive Loss	Comprehensive Loss Comprehensive loss consists of net loss and changes in unrealized gains and losses on investments classified as available-for-sale. For the three months ended March 31, 2022 and 2021 , the Company’s unrealized gains and losses on available-for-sale investments represent the only component of other comprehensive loss that are excluded from the reported net loss and that are presented in the condensed statements of operations and comprehensive loss. Accumulated other comprehensive loss is presented in the accompanying condensed balance sheets as a component of stockholders' equity.
Net Loss per Share	Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration for potential dilutive common shares. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, common stock options, and restricted stock units are considered to be potentially dilutive securities. Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share as the inclusion of all potential dilutive common shares would have been anti-dilutive. Net loss per share was determined as follows (in thousands, except share and per share data): Three Months Ended March 31, 2022 2021 Net loss $ ( 16,679 ) $ ( 10,694 ) Weighted average common stock outstanding used to compute net loss per share, basic and diluted 35,023,297 34,336,433 Net loss, basic and diluted $ ( 0.48 ) $ ( 0.31 ) The following potentially dilutive securities outstanding have been excluded from the computation of diluted weighted average shares outstanding because such securities have an antidilutive impact due to the Company's net loss: March 31, 2022 2021 Common stock options 4,197,518 4,288,835 Restricted stock units 1,123,515 251,138 5,321,033 4,539,973
Segment and Geographical Information	Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Primarily all of the Company’s long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment. All of the Company’s revenue was in the United States for the three months ended March 31, 2022 and 2021, based on the shipping location of the external customer.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2022
Summary of Significant Accounting Policies [Abstract]
Net Loss Per Share Determination	Three Months Ended March 31, 2022 2021 Net loss $ ( 16,679 ) $ ( 10,694 ) Weighted average common stock outstanding used to compute net loss per share, basic and diluted 35,023,297 34,336,433 Net loss, basic and diluted $ ( 0.48 ) $ ( 0.31 )
Schedule of Potentially Dilutive Securities Outstanding Excluded from Diluted Weighted Average Shares Outstanding	March 31, 2022 2021 Common stock options 4,197,518 4,288,835 Restricted stock units 1,123,515 251,138 5,321,033 4,539,973

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Measurements [Abstract]
Financial Liabilities Measure on a Recurring Basis	March 31, 2022 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 9,257 $ — $ — $ 9,257 $ 9,257 $ — $ — $ 9,257 December 31, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 21,062 $ — $ — $ 21,062 $ 21,062 $ — $ — $ 21,062

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2022
Balance Sheet Components [Abstract]
Schedule of Inventories	March 31, December 31, 2022 2021 Raw materials $ 3,031 $ 2,447 Finished products 14,708 15,437 17,739 17,884 Less: Reserve for excess and obsolete ( 13 ) ( 33 ) $ 17,726 $ 17,851
Schedule of Accrued Liabilities	March 31, December 31, 2022 2021 Accrued payroll and related expenses $ 9,889 $ 13,898 Provision for sales returns 481 359 Accrued professional services 2,290 2,039 Operating lease liability 1,519 1,294 Accrued royalty expense 682 687 Deferred revenue 522 157 Accrued travel expenses 637 590 Accrued clinical expenses 73 99 Accrued other expenses 651 679 Total $ 16,744 $ 19,802

Long-term Debt (Tables)

Long-term Debt (Tables)	3 Months Ended
	Mar. 31, 2022
Long-term Debt [Abstract]
Future Maturities Under the Term Loan Agreement	Period Ending December 31: Amount 2022 $ 5,675 2023 25,749 2024 21,457 52,881 Less: Amount representing interest ( 3,881 ) Less: Amount representing debt discount and debt issuance costs ( 270 ) Present value of minimum payments $ 48,730

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies [Abstract]
Balance Sheet Information	March 31, December 31, Operating Lease: 2022 2021 Operating lease right-of-use assets in other non-current assets $ 4,977 $ 5,219 Operating lease liabilities in accrued liabilities $ 1,519 $ 1,294 Operating lease liabilities in other liabilities 6,225 5,747 Total operating lease liabilities $ 7,744 $ 7,041
Operating Lease Maturities	Period Ending December 31: Amount 2022 $ 1,201 2023 1,967 2024 1,764 2025 882 2026 904 2027 and thereafter 2,769 Total lease payments $ 9,487 Less: interest ( 1,743 ) Total lease liabilities $ 7,744

Stock Option Plans (Tables)

Stock Option Plans (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Shares Available for Issuance	Number of Shares Balances, December 31, 2021 2,477,212 Authorized 1,399,235 Granted / Awarded ( 1,132,907 ) Cancelled 30,381 Balances, March 31, 2022 2,773,921
Stock Option Activity	Options Outstanding Number of Weighted Average Weighted Average Remaining Contractual Term Aggregate Intrinsic Shares Exercise Price (Years) Value Balances, December 31, 2021 3,780,939 $ 20.45 6.71 $ 91,900 Options granted 473,280 36.44 Options exercised ( 35,453 ) 4.74 Options cancelled ( 21,248 ) 40.47 Balances, March 31, 2022 4,197,518 $ 22.28 6.88 $ 88,620 Vested and exercisable at March 31, 2022 2,836,804 $ 14.53 6.00 $ 78,941 Vested and expected to vest at March 31, 2022 4,197,518 $ 22.28 6.88 $ 88,620
Summary of RSU Activity	Number of Restricted Stock Units Weighted Average Grant Date Fair Value Balances, December 31, 2021 530,274 $ 53.01 Awards granted 659,627 36.38 Awards vested ( 57,253 ) 49.86 Awards canceled ( 9,133 ) 47.83 Balances, March 31, 2022 1,123,515 $ 43.45 Expected to vest at March 31, 2022 1,123,515 $ 43.45
Stock-Based Compensation Expense Relating to Stock Options to Employees and Nonemployees	Three Months Ended March 31, 2022 2021 Cost of goods sold $ 221 $ 158 Research and development expenses 1,069 689 Selling, general and administrative expenses 3,688 2,686 $ 4,978 $ 3,533
Common Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Fair Value Assumptions	Three Months Ended March 31, 2022 2021 Expected term (in years) 6.25 5.25 - 6.25 Expected volatility 48.2 % 45.0 % - 50.4 % Risk-free interest rate 1.60 % - 1.77 % 0.41 % - 0.98 % Dividend yield —% —%
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Fair Value Assumptions	Three Months Ended March 31, 2022 2021 Expected term (in years) 0.50 0.50 Expected volatility 51.6 % 46.9 % Risk-free interest rate 0.07 % 0.10 % Dividend yield —% —%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Voluntary Recall (Narrative) (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Inventory [Line Items]
Inventories	$ 17,726,000	$ 17,851,000
Contingent liabilities requiring accrual	0	0
ENROUTE [Member]
Inventory [Line Items]
Contingent liabilities requiring accrual	$ 11,000	11,000
Voluntary Recall
Inventory [Line Items]
Inventories		$ 335,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Revenue Recognition (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Summary of Significant Accounting Policies [Abstract]
Unbilled receivables	$ 255	$ 87

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Income Taxes (Narrative) (Details)	Mar. 31, 2022USD ($)
Summary of Significant Accounting Policies [Abstract]
Provision for income taxes	$ 0

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Segment and Geographical Information (Narrative) (Details)	3 Months Ended
	Mar. 31, 2022segment
Summary of Significant Accounting Policies [Abstract]
Number of reportable segments	1
Number of operating segments	1

Summary of Significant Accoun_8

Summary of Significant Accounting Policies (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Summary of Significant Accounting Policies [Abstract]
Net loss	$ (16,679)	$ (10,694)
Weighted average common stock outstanding used to compute net loss per share, basic and diluted (in shares)	35,023,297	34,336,433
Net loss, basic and diluted (in USD per share)	$ (0.48)	$ (0.31)

Summary of Significant Accoun_9

Summary of Significant Accounting Policies (Schedule of Potentially Dilutive Securities Not Included in Calculation of Earnings per Share) (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,321,033	4,539,973
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,197,518	4,288,835
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,123,515	251,138

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0		$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0		$ 0
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	9,257,000	$ 21,062,000
Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	9,257,000	21,062,000
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	9,257,000	21,062,000
Recurring [Member] | Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 9,257,000	$ 21,062,000

Balance Sheet Components (Narra

Balance Sheet Components (Narrative) (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Inventory [Line Items]
Work-in-process inventories	$ 0	$ 0
Short-term Investments	0	0
Money Market Funds [Member]
Inventory [Line Items]
Cash Equivalents, at Carrying Value	$ 9,257,000	$ 21,062,000

Balance Sheet Components (Sched

Balance Sheet Components (Schedule of Inventory) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Balance Sheet Components [Abstract]
Raw materials	$ 3,031	$ 2,447
Finished products	14,708	15,437
Inventory, gross	17,739	17,884
Less: Reserve for excess and obsolete	(13)	(33)
Inventories	$ 17,726	$ 17,851

Balance Sheet Components (Accru

Balance Sheet Components (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Balance Sheet Components [Abstract]
Accrued payroll and related expenses	$ 9,889	$ 13,898
Provision for sales returns	481	359
Accrued professional services	2,290	2,039
Operating lease liability	1,519	1,294
Accrued royalty expense	682	687
Deferred revenue	522	157
Accrued travel expenses	637	590
Accrued clinical expenses	73	99
Accrued other expenses	651	679
Total	$ 16,744	$ 19,802

Long-term Debt - Stifel Bank (N

Long-term Debt - Stifel Bank (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended
	Oct. 31, 2020	Mar. 31, 2022
Term Loan [Member]
Subsequent Event [Line Items]
Debt pay off	$ 46,674,000
Prepayment premium fee	305,000
Debt interest	365,000
Facility fee	2,191,000
Loss on debt extinguishment	(1,119,000)
Letter of Credit [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Facility amount		$ 50,000,000
Amount drawn on facility	$ 49,000,000
Aggregate outstanding principal balance		$ 49,000,000
Annual interest rate		4.75%
Percent of original principal threshold		0.75%
Redemption amount		$ 375,000
Debt default rate		5.00%
Stated interest rate		4.75%
Secured Revolving Credit Facility [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Facility amount		$ 50,000,000
Secured Revolving Credit Facility, Subfacility [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Facility amount		2,000,000
Minimum [Member] | Letter of Credit [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Restricted Cash		$ 20,000,000
Minimum [Member] | Letter of Credit [Member] | Prime Rate [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Variable interest rate		0.50%
Maximum [Member] | Letter of Credit [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Restricted Cash		$ 60,000,000
Maximum [Member] | Letter of Credit [Member] | Prime Rate [Member] | Stifel Bank [Member]
Subsequent Event [Line Items]
Variable interest rate		0.75%

Long-term Debt (Future Maturiti

Long-term Debt (Future Maturities Under the Term Loan) (Details) $ in Thousands	Mar. 31, 2022USD ($)
Long-term Debt [Abstract]
2022	$ 5,675
2023	25,749
2024	21,457
Long-term debt, gross before accretion of closing fees	52,881
Less: Amount representing interest	(3,881)
Less: Amount representing debt discount and debt issuance costs	(270)
Present value of minimum payments	$ 48,730

Commitments and Contingencies -

Commitments and Contingencies - Lease (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	May 31, 2021
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 4,977		$ 5,219	$ 3,307
Operating Lease, Liability	7,744		$ 7,041	$ 3,307
Operating lease costs	$ 365	$ 217
Weighted average discount rate	6.50%
Weighted average remaining lease term	5 years 11 months 8 days
Operating Lease, Cash Paid	$ (704)	$ 203
Headquarters [Member]
Lessee, Lease, Description [Line Items]
Renewal term	5 years
Additional Office, Laboratory And Manufacturing Space [Member]
Lessee, Lease, Description [Line Items]
Renewal term	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Purchase Obligation and Contingencies (Narrative) (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Commitments and Contingencies [Abstract]
Purchase obligation	$ 6,481,000
Contingent liabilities requiring accrual	$ 0	$ 0

Commitments and Contingencies_3

Commitments and Contingencies (Balance Sheet Information) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	May 31, 2021
Commitments and Contingencies [Abstract]
Operating lease right-of-use asset in other non-current assets	$ 4,977	$ 5,219	$ 3,307
Operating lease liability in accrued liabilities	1,519	1,294
Operating lease liability in other liabilities	6,225	5,747
Total operating lease liabilities	$ 7,744	$ 7,041	$ 3,307

Commitments and Contingencies_4

Commitments and Contingencies (Operating Lease Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	May 31, 2021
Commitments and Contingencies [Abstract]
2022	$ 1,201
2023	1,967
2024	1,764
2025	882
2026	904
Thereafter	2,769
Total lease payments	9,487
Less: interest	(1,743)
Total lease liabilities	$ 7,744	$ 7,041	$ 3,307

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Stockholders’ Equity [Abstract]
Preferred shares authorized (in shares)	5,000,000	5,000,000
Preferred shares (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, shares issued (in shares)	0	0
Shares authorized (in shares)	100,000,000	100,000,000
Par value (in USD per share)	$ 0.001	$ 0.001
Shares issued (in shares)	35,073,602	34,980,896
Shares outstanding (in shares)	35,073,602	34,980,896
Dividends declared	$ 0
Stockholder Short Swing Profits		$ 32,000

Stock Option Plans (Narrative)

Stock Option Plans (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expensed not yet recognized	$ 22,618
Compensation expensed not yet recognized, period for recognition	2 years 9 months 18 days
ISO and NSO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise threshold as a percentage of fair value of shares	10.00%
Option term	10 years
Option vesting term	4 years
ISO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise threshold as a percentage of fair value of shares	100.00%
NSO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise threshold as a percentage of fair value of shares	85.00%
Common Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of options exercised	$ 1,170
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting term	4 years
Compensation expensed not yet recognized, period for recognition	3 years 6 months 7 days
Unrecognized compensation costs of unvested RSUs	$ 45,249
Maximum [Member] | ISO and NSO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise threshold as a percentage of fair value of shares	110.00%
2019 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares) | shares	6,416,747
Compensation expensed not yet recognized, period for recognition	1 month 17 days
Unrecognized compensation costs related to the ESPP	$ 129
2019 Equity Incentive Plan [Member] | Common Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under employee stock purchase plan (in shares) | shares	166,951
Shares available for future issuance (in shares) | shares	1,271,905

Stock Option Plans (Activity Un

Stock Option Plans (Activity Under Compensation Plan) (Details) - 2019 Equity Incentive Plan [Member]	3 Months Ended
	Mar. 31, 2022shares
Shares Available for Grant
Beginning balance (in shares)	2,477,212
Authorized (in shares)	1,399,235
Granted/Awarded (in shares)	(1,132,907)
Canceled (in shares)	30,381
Ending balance (in shares)	2,773,921

Stock Option Plans (Stock Optio

Stock Option Plans (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares
Beginning balance (in shares)	3,780,939
Options granted (in shares)	473,280
Options exercised (in shares)	(35,453)
Options cancelled (in shares)	(21,248)
Ending balance (in shares)	4,197,518	3,780,939
Vested and exercisable (in shares)	2,836,804
Vested and expect to vest (in shares)	4,197,518
Weighted Average Exercise Price
Beginning balance (in USD per share)	$ 20.45
Options granted (in USD per share)	36.44
Options exercised (in USD per share)	4.74
Options cancelled (in USD per share)	40.47
Ending balance (in USD per share)	22.28	$ 20.45
Vested and exercisable (in USD per share)	14.53
Vested and expected to vest (in USD per share)	$ 22.28
Weighted Average Remaining Contractual Term (in Years)
Awards outstanding	6 years 10 months 17 days	6 years 8 months 15 days
Vested and exercisable	6 years
Vested and expected to vest	6 years 10 months 17 days
Aggregate Intrinsic Value (in thousands)
Awards outstanding	$ 88,620	$ 91,900
Vested and exercisable	78,941
Vested and expected to vest	$ 88,620

Stock Option Plans (RSUs) (Deta

Stock Option Plans (RSUs) (Details) - Restricted Stock Units [Member]	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Number of Restricted Stock Units
Beginning balance (in shares) | shares	530,274
Restricted stock granted (in shares) | shares	659,627
Restricted stock vested (in shares) | shares	(57,253)
Restricted stock forfeited (in shares) | shares	(9,133)
Ending balance (in shares) | shares	1,123,515
Expected to vest (in shares) | shares	1,123,515
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 53.01
Restricted stock granted (in USD per share) | $ / shares	36.38
Restricted stock vested (in USD per share) | $ / shares	49.86
Restricted stock forfeited (in USD per share) | $ / shares	47.83
Ending balance (in USD per share) | $ / shares	43.45
Expected to vest (in USD per share) | $ / shares	$ 43.45

Stock Option Plans (Fair Value

Stock Option Plans (Fair Value of Stock Options) (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Common Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	48.20%	45.00%
Expected volatility, maximum		50.40%
Risk-free interest rate, minimum	1.60%	0.41%
Risk-free interest rate, maximum	1.77%	0.98%
Dividend yield
Common Stock Options [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 3 months	5 years 3 months
Common Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		6 years 3 months
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months	6 months
Expected volatility	51.60%	46.90%
Risk-free interest rate	0.07%	0.10%
Dividend yield

Stock Option Plans (Stock-based

Stock Option Plans (Stock-based Compensation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 4,978	$ 3,533
Cost of Goods Sold [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	221	158
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,069	689
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,688	$ 2,686

401(k) Plan (Details)

401(k) Plan (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
401(k) Plan [Abstract]
Percentage employee contribution	90.00%
Employer discretionary contribution	$ 589	$ 366
Employer contribution match percentage	50.00%		50.00%
Percent of matching contribution of the employee's pay	6.00%		5.00%