**2. Types of TMVR**

There are three main types of TMVR: 1) valve-in-valve (ViV) for severe mitral valve disease due to degenerated mitral bioprosthetic valves, 2) valve-in-ring (ViR) for failed surgical repairs with annuloplasty rings, and 3) valve-in-mitral annular calcifications (ViMAC) for native mitral valve disease with severe MAC who are poor surgical candidates [1]. Mitral ViV for high surgical risk patients was approved by the Food and Drug Administration (FDA) in the United States (US) in 2017, while mitral ViR and ViMAC remain off-label at this current time [4]. The role of TMVR in native mitral valve disease, whether MR or mitral stenosis, is currently being studied using various device types and designs. We will discuss these separately under the dedicated TMVR device section.
