Surgery for severe mitral regurgitation and left ventricular failure: what do we really know?

In ischemic and nonischemic cardiomyopathy, functional mitral regurgitation (MR) results from geometric abnormalities of the ventricle, which result in dysfunction of a morphologically normal mitral valve. Enlargement of the left ventricle causes geometric MR through annular dilation, increase in the interpapillary muscle distance, amplified leaflet tethering (elongation and stretch on the chordae tendinae), and decreased closing forces because of muscle weakness and asynchrony of papillary muscle contractile timing. The final common pathway of MR is a failure of coaptation of the morphologically normal leaflets and resultant central MR. These abnormalities can be favorably influenced by antiremodeling pharmacologic therapy and in selected cases by cardiac resynchronization therapy. Surgical repair of functional geometric MR with an undersized complete rigid annuloplasty ring can abolish MR and is associated with improved functional status and left ventricular remodeling. It is unclear if surgery is associated with improved survival in this setting. There is a pressing need for well-conducted prospective randomized clinical trials to quantify the benefits of surgical repair of functional geometric MR.