Mechanisms of recurrent functional mitral regurgitation after mitral valve repair in nonischemic dilated cardiomyopathy: importance of distal anterior leaflet tethering.

BACKGROUND Recurrent functional mitral regurgitation (MR) has been reported after mitral valve repair with annuloplasty in patients with dilated cardiomyopathy, but the mechanism is not understood completely. The authors sought to identify abnormalities of the mitral valve and left ventricle that are associated with recurrent MR after mitral annuloplasty. METHOD AND RESULTS In 104 patients with idiopathic dilated cardiomyopathy who underwent annuloplasty for functional MR, basal mitral anterior leaflet angle, distal mitral anterior leaflet angle (ALAtip), posterior leaflet angle, coaptation depth, tenting area, mitral annular dimensions, left ventricular volumes, and MR severity were quantified by echocardiography before surgery and at 6-month intervals after it. Compared with patients without MR recurrence (n=79), patients with recurrent MR (defined as > or =2+) (n=25) had greater ALAtip (P<0.001) and basal mitral anterior leaflet angle (P<0.001), greater coaptation depth and tenting area (P<0.001), larger left ventricular volumes (P<0.001), and worse left ventricular ejection fraction (P<0.05) but similar mitral annular dimensions and postoperative exaggeration in posterior leaflet angle. Multivariable analysis identified postoperative ALAtip as the major determinant of postoperative MR. Receiver operator characteristic curves identified preoperative ALAtip as the best predictor of MR recurrence (area under curve, 0.98). For ALA(tip) >25 degrees, the sensitivity, specificity, and positive and negative predictive values in predicting recurrent MR were 88%, 94%, 82%, and 93%, respectively. Three distinct patterns of anterior leaflet tethering (minimal, basal, and distal) with an increasing risk of recurrent MR were identified. CONCLUSIONS Posterior leaflet tethering is invariable after mitral annuloplasty, rendering postoperative mitral competence highly dependent on distal anterior leaflet mobility.