Anterior mitral leaflet interventions and valvular-ventricular mechanoenergetics

Abstract

Patients with functional mitral regurgitation and poor left ventricular function face an increased risk of morbidity and mortality. Although mitral repair techniques exist, valve replacement is often favored due to reduced reoperation risk. Preserving the subvalvular apparatus during replacement is crucial for maintaining left ventricular function, though most methods retain only the posterior leaflet. Modifying or removing the anterior mitral leaflet, typically to avoid left ventricular outflow tract obstruction, may impair left ventricular function—an area not well understood.

This study developed a normothermic beating-heart ovine model to examine the acute effects of mitral interventions on left ventricular function across three experiments:

1. Experiment 1 evaluated the effects of different bioprosthetic interstrut distances on the native anterior mitral leaflet movement in five sheep. Wider inter-strut distance subtending the anterior leaflet partially protected against left ventricular outflow tract obstruction.

2. Experiment 2 involved 14 sheep with mechanical mitral valve insertion while retaining the native mitral valve. Releasable snares reefed and released the anterior leaflet to the annulus, showing that reefing altered left ventricular hemodynamics, reduced contractility, and increased left ventricular sphericity.

3. Experiment 3 in six sheep evaluated splitting the anterior leaflet and shortening the annulo-papillary distance. These interventions acutely impaired left ventricular contractility and hemodynamics.

Overall, the research demonstrated that commonly used anterior leaflet interventions can significantly affect left ventricular function. The findings underscore the importance of preserving the entire valvular-ventricular apparatus and provide a foundation for improving valve designs and surgical techniques.