Mechanisms of severe mitral regurgitation in mitral valve prolapse determined from analysis of operatively excised valves.

Certain clinical and mitral valvular morphologic findings are described in 83 patients (age 26 to 79 years [mean, 60]; 26 women [31%] and 57 men [69%]) with mitral valve prolapse (MVP) and mitral regurgitation (MR) severe enough to warrant mitral valve replacement. All 83 operatively excised valves were examined by the same person, and all excised valves had been purely regurgitant (no element of stenosis). No patients had hemodynamic evidence of dysfunction of the aortic valve. In each valve a portion of the posterior mitral leaflet was elongated such that the distance from the distal margin to basal attachment of this leaflet was similar to the distance from the distal margin of the anterior leaflet to its basal attachment to the left atrial wall. Two major mechanisms for the severe MR were found: dilatation of the mitral anulus with or without rupture of chordae tendineae and rupture of chordae tendineae with or without dilatation of the mitral anulus. Of the 83 patients, 48 (58%) had both dilated anuli (greater than 11 cm in circumference) and ruptured chordae tendineae; 16 (19%) had dilated anuli without ruptured chordae, and 16 (19%) had ruptured chordae without significant anular dilatation. In three patients the anulus was not dilated, nor were chordae ruptured, and therefore the mechanism of the MR is uncertain. Mitral chordal rupture was nearly as frequent in the 64 patients with clearly dilated anular circumferences as in the 19 patients with normal or insignificantly dilated anular circumferences (less than or equal to 11 cm).