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Asset Acquisition and Business Combination - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 18, 2019	Feb. 29, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Research and development expense			$ 8,176	$ 5,247	$ 16,149	$ 9,624
Goodwill			12,026		12,026		$ 12,026
Payments for contingent consideration					2,619
Biotronik Asset Acquisition [Member]
Business Acquisition [Line Items]
Consideration paid in cash							10,000
Equity interests issued and issuable							$ 5,000
Consideration transferred					15,000
Potential milestone payments payable			10,000		10,000
Biotronik Asset Acquisition [Member] \| Intellectual Property [Member]
Business Acquisition [Line Items]
Research and development expense					15,000
Rhythm Xience [Member]
Business Acquisition [Line Items]
Consideration paid in cash	$ 3,000				3,000
Contingent consideration liability	$ 7,500		13,400		13,400
Date of business acquisition	Jun. 18, 2019
Goodwill			12,026		12,026
Payments for contingent consideration					2,600
Business combination contingent consideration liability change in amount			$ 600	$ 0	1,600	$ 0
Rhythm Xience [Member] \| Earnout Consideration [Member]
Business Acquisition [Line Items]
Potential milestone payments payable	$ 17,000
Series D Convertible Preferred Stock [Member] \| Biotronik Asset Acquisition [Member]
Business Acquisition [Line Items]
Business consideration, number of equity interests issued and issuable							273,070
Equity interests issued and issuable					$ 5,000
Series D Convertible Preferred Stock [Member] \| Rhythm Xience [Member]
Business Acquisition [Line Items]
Business consideration, number of equity interests issued and issuable					119,993
Series D Convertible Preferred Stock [Member] \| Rhythm Xience [Member] \| Earnout Consideration [Member]
Business Acquisition [Line Items]
Equity interests issued and issuable		$ 2,000