Mitral valve cleft gapping mechanism in functional mitral regurgitation: An in-vitro study

Abstract

Background and aimGapping formation of the mitral valve cleft is unknown. The objective of this study was to quantify the geometry of mitral valve cleft coaptation in the asymmetric and symmetric papillary muscles (PMs) positions in a dilated annulus in order to reveal mitral valve gapping mechanism. MethodsNine fresh porcine mitral valves with the posterior leaflet clefts were sutured onto a saddle-shaped dilated annulus in an in-vitro experiment to simulate mitral valve closure at hydrostatic pressure. PMs were adjusted to the normal position, and subsequently to positions of asymmetric and symmetric PM displacement. Sonomicrometry was used to measure positions of the lateral and medial clefts. ResultsPM displacement tethered the leaflets. Both the opening angle and contact angle of the lateral cleft, but not of the medial cleft, increased in the asymmetric PM displacement. Neither the opening angle nor contact angle of both clefts increased in the symmetric PM displacement. ConclusionsDisplacement of the postero-medial PM moves the posterior leaflet medially and impairs coaptation of the lateral cleft, but not medial cleft, which suggest that the medial cleft displacement in the asymmetric PM position is another mechanism of gap formation in addition to leaflet tenting due to apical leaflet displacement. Symmetric PM displacement cause leaflet tenting, but doesn’t impair the leaflet cleft coaptation, which suggest that the asymmetric PM position is even worse than the symmetric PM position.