Patient selection for transcatheter mitral valve implantation: why is it so hard to find patients?

Both transcatheter mitral valve repair and replacement have been introduced in patients with severe mitral regurgitation (MR). However, while transcatheter mitral valve repair is rapidly evolving, transcatheter mitral valve implantation (TMVI) has had a slow development path. One of the main reasons for this is the challenge to find good candidates for this therapy. Although scarce data exist for patient inclusion and/or exclusion criteria and patient screening, the current rejection rate for TMVI is reported to be around 60%. The rejection could be due to: 1) the restriction of the technique to patients at high and extreme surgical risk, as well as the exclusion of patients in whom intervention will be futile, 2) the complexity of the procedure and the anatomical constraints which are high in patients with native valve disease and in those with severe annular calcification, and 3) low procedural safety with left ventricular outflow tract obstruction as the most feared complication. In the future, new transcatheter heart valve platforms and designs are expected to be available which will reduce the periprocedural complications. Furthermore, evaluation of the mitral valve anatomy before and during the procedure may be more accurate, and more evidence on the best clinical practice is expected, including a comparison of TMVI with transcatheter mitral valve repair and surgical intervention, as well as the long-term follow-up. This will facilitate determining the subset of patients who may potentially benefit from this technology.