Preventing “Dock Drop” During Transcatheter Mitral Valve Replacement with the SAPIEN M3 System

Abstract Transcatheter mitral valve replacement (TMVR) with the SAPIEN M3 system provides an important therapeutic pathway for patients with severe mitral regurgitation who are unsuitable for conventional surgery or edge-to-edge repair. A primary procedural challenge with this transseptal system is "dock drop"—the abrupt inferior displacement or loss of annular engagement of the docking system during unsleeving or release. This complication is particularly prevalent in valve-in-ring procedures or in patients with challenging subvalvular geometry, such as an increased annulus-to-papillary muscle distance. While the SAPIEN M3 docking mechanism is designed to anchor within the native annulus or a prior surgical ring, practical intraprocedural strategies to manage docking instability remain poorly defined in current literature. This article details a novel, step-by-step technique using dual transseptal sheath alignment to stabilize the docking system. By utilizing a secondary sheath for mechanical support, the operator can ensure precise alignment and prevent displacement during the critical stages of unsleeving. The technique is illustrated through a complex valve-in-ring TMVR procedure, in which unfavorable subvalvular anatomy posed a high risk of dock instability. This dual-sheath approach provides a reproducible method to enhance the stability of the SAPIEN M3 dock, ultimately facilitating safer, more predictable valve implantation in anatomically demanding cases.