Non-rheumatic 'subvalvar' mitral regurgitation. Surgical pathology and results of operation in 37 patients.

Thirty-seven patients with non-rheumatic subvalvar mitral regurgitation are reported, representing 16% of all patients with mitral regurgitation submitted to open operation over a five-and-a-half-year period. In 22 older patients with `idiopathic' chordal lesions, the commonest finding was rupture of chordae to the posterior leaflet. The aortic leaflet chordae were most frequently involved following myocardial infarction (7 patients) or bacterial endocarditis (3 patients). Three other younger patients had ruptured chordae and two patients had rupture of the posteromedial papillary muscle following acute myocardial infarction. The mitral valve was repaired in 16 patients with ruptured chordae, of whom only eight obtained a satisfactory late result. In the other 21 patients the valve was replaced with a mounted aortic homograft or a Starr-Edwards prosthesis. It is concluded that mitral valve repair should be reserved for patients with symmetrical rupture of the chordae controlling the centre of the posterior leaflet, as regurgitation may reappear after other forms of repair due to progressive rupture of other abnormal chordae or breakdown of the repair. The early and late mortality in the patients with a definite antecedent myocardial infarction was much higher than in the other groups, and emergency valve replacement soon after rupture of the papillary muscle was unsuccessful in both patients.