FIXED ANTERIOR LEAFLET EDGE 3‐D POSITION DURING END‐SYSTOLE: AN IMPORTANT COMPONENT OF MITRAL REGURGITATION

Introduction: With so much redundant mitral leaflet tissue compared to annular area, why does posterior leaflet edge displacement during systole only on the order of only a few millimeters lead to mitral regurgitation (MR)? Methods: Five sheep had mitral annular, posterior, and anterior leaflet edge markers inserted. A suture from the central scallop of the posterior mitral leaflet (PML) was exteriorized in a radial direction. After baseline data acquisition, the suture was pulled, drawing the PML towards the lateral wall (PULL) and creating 3+ MR. The 3D coordinates of both leaflets were computed with the origin at the annular saddle‐horn, y‐axis through the apex, x‐axis toward the lateral annulus, and z‐axis toward the posterior commissure. Results: Displacement of the PML edge with PULL produced MR (0.5+ to 3‐4+, p<0.001), but only minimal changes in ES anterior leaflet edge position (Table, mean± SD). Conclusions: Anterior leaflet edge 3D position at ES is fixed primarily by annular and chordal attachments and anterior leaflet dimensions, not by coaptation with the posterior leaflet. Thus, any condition which pulls the posterior leaflet edge more than a few millimeters away from this fixed position (e.g., dilated or ischemic cardiomyopathy) can produce MR because the anterior leaflet edge is fixed in 3D space and does not acutely track to the new position of the posterior leaflet edge, despite the known leaflet redundancy. This intriguing finding provides better mechanistic understanding of what is required to restore mitral competency, using either interventional or surgical methods.