Medtronic on Tuesday said it would buy U.S. medical device company Twelve for $458 million, to augment the Ireland medical technology company’s existing capabilities in the transcatheter mitral space.

“We have followed the transcatheter mitral…”

Medtronic will pay privately-owned Twelve $408 million at closing and $50 million on achievement of a particular milestone. The product line will be part of the Medtronic Cardiac and Vascular Group’s Coronary & Structural Heart division. It acquired RF Surgical Systems for $235 million just last month. It also invested in and gained an option to purchase Cephea Valve Technologies, though financial details were undisclosed.

Redwood City, Calif.-based Twelve’s transcatheter mitral valve replacement device is designed to fix a mitral valve (between the heart’s left atrium and the left ventricle) that doesn’t close normally, letting blood flow the wrong way and eventually leading to heart failure. Medtronic and Edwards already dominate the market for aortic valve replacement performed without cracking open the chest, which will have sales of $3 billion by 2018, according to Danielle Antalffy, an analyst at Leerink Partners.

Edwards CEO Michael Mussallem said the acquisition is meant to complement internal efforts at developing a TMVR device dubbed Fortis, but development was paused in May, after safety concerns were detected in an early feasibility studies of about 20 patients.