Analysis of the mitral coaptation zone in normal and functional regurgitant valves

Functional mitral regurgitation (FMR) is associated with leaflet displacement and tethering. Little is known about regional coaptation zones, including variations in coaptation length (CL) and contributions of anterior and posterior leaflets. Regional coaptation zones were analyzed in patients with normal mitral valves and with FMR.

Cardiac surgery patients underwent a three-dimensional transesophageal echocardiography. Four-dimensional volumetric datasets were acquired with Doppler interrogation. Offline analysis was performed. Orthogonal views were extracted in diastole and systole. Leaflet dimensions and coaptation distance and depth were examined for posterior and apical displacement of the coaptation zones.

Twenty patients were analyzed (10 normal and 10 with 2 to 4+ FMR). Anterior leaflet CL was greater than posterior leaflet CL: 2.2+/-0.6 mm versus 0.9+/-0.3 mm in region 1, 3.2+/-0.7 mm versus 1.2+/-0.6 mm in region 2, and 1.8+/-0.4 mm versus 0.6+/-0.3 mm in region 3 (p<0.001). The FMR was associated with shorter leaflet CLs, with a mean anterior CL of 1.7+/-0.4 mm versus 3.1+/-0.4 mm (p=0.04), and a mean posterior CL of 0.7+/-0.3 mm versus 1.1+/-0.3 mm (p=0.03). The biggest difference in CLs was in A2-P2. Coaptation distance and depth were higher in the FMR group: 21.7+/-1.0 mm versus 17.9+/-1.0 mm (p=0.01), and 8.6+/-0.7 mm versus 5.0+/-0.7 mm (p<0.01).

Mitral valve leaflet CL is asymmetric in normal valves, with anterior dominance. Functional mitral regurgitation is associated with a relocated coaptation zone, regional changes, and diminished coaptation. These data suggest an "anterior leaflet reserve." Posterior movement of the coaptation line compensates for annular dilation and presumed left ventricular enlargement in order to maintain competency until inadequate anterior leaflet CL occurs.