Abstract
Transcatheter mitral valve intervention (TMVI) has emerged as a potential alternative to surgery for patients with mitral annular calcification (MAC)-associated mitral valve disease, a population often deemed high-risk due to clinical and anatomic complexities. However, MAC also presents significant challenges to TMVI itself. In transcatheter edge-to-edge repair (TEER), procedural success may be limited by fibrotic and short leaflets, reduced mitral valve area, and subvalvular calcium protrusion. Transcatheter mitral valve replacement (TMVR) poses further anatomical hurdles, including a small, eccentric, or non-conforming annuli; insufficient MAC to ensure anchoring; narrow aortomitral angle; septal hypertrophy; elongated anterior mitral leaflet predisposing to left ventricular outflow tract (LVOT) obstruction; and heterogeneous MAC morphology leading to paravalvular leak or suboptimal fixation. Mechanical injury to adjacent structures such as the circumflex artery and atrioventricular groove is also a concern. Balloon-expandable valves, used off-label for TMVR, may be delivered via transapical, transfemoral, transseptal, or hybrid transatrial approaches. While early data show high mortality for valve-in-MAC (ViMAC) procedures, a shift toward transfemoral transseptal access has improved outcomes. The hybrid transatrial approach offers advantages including resection of the anterior leaflet, septal myectomy, and reinforcement of the valve skirt with Teflon felt. Among dedicated self-expanding TMVR systems, only Tendyne has both CE mark and US Food and Drug Administration (FDA) approval and is delivered transapically. New transfemoral transseptal systems-such as Intrepid, AltaValve, and Cephea-are under active investigation. Techniques like LAMPOON (Laceration of the Anterior Mitral leaflet to Prevent Outflow ObstructioN) and BATMAN (Balloon-Assisted Translocation of the Mitral Anterior Leaflet) have been developed to mitigate the risk of fatal LVOT obstruction. Despite progress, mid-term mortality after ViMAC TMVR remains high. Continued innovations in technique, device design, and patient selection are critical to establishing TMVI as a viable treatment for MAC-associated mitral valve disease.