The posterior mitral leaflet overhang: A rare yet possible complication of percutaneous mitral valve procedures.

The two surgical options for mitral valve regurgitation are replacement and repair, with annuloplasty being the cornerstone of correction. In cases of repair failure, especially in high surgical risk patients, transcatheter mitral valve-in-ring (MViR) procedures represent emerging and challenging options. Among the several complications linked to this treatment, this paper delves into the role that native mitral leaflets may play in precipitating acute bioprosthesis dysfunction in the MViR procedure. The literature extensively covers complications related to the anterior leaflet, including risks such as outflow tract obstruction and residual mitral insufficiency due to interaction between native and prosthetic leaflets. Conversely, complications involving the posterior leaflet are less understood and often overlooked. In this gap in the literature, we present a clinical case highlighting how a redundant native posterior mitral leaflet can unexpectedly lead to acute severe mitral insufficiency by interfering with prosthetic leaflets.