The pathology of mitral valve prolapse.

The gross criteria for diagnosing prolapsing mitral valve are: 1. interchordal hooding of the involved leaflets, 2. hooding or doming of leaflets towards the left atrium, 3. elongation of the involved leaflets resulting in an increase in valve area, 4. dilatation of the valve annulus in patients with severe mitral regurgitation. The posterior leaflet is most frequently affected. The involved leaflets, in general, are thickened, soft, greyish white and have a smooth atrial surface. Chordae tendineae are described as elongated, tortuous and attenuated or thinned. Deviations from normal chordal insertion have recently been observed which possibly appear to represent the underlying abnormality. Microscopic findings include significant thickening of the spongiosa and the fibrosa, changes in dense collagen fibers in the atrialis layer, occasionally, with fibrin platelet deposits. Histochemical characterization of changes in the spongiosa may also be helpful in the diagnosis. Ultrastructurally, there may be changes in collagen and elastic fibers as well as myxoid areas. On comparison of findings in surgically-removed mitral valves with those of control specimens from autopsy patients with no cardiac abnormalities, the length of the anterior and posterior leaflet as well as the annular ring diameter was larger in the valves with prolapse. Two-dimensional echocardiography accurately assessed leaflet length when compared to morphologic measurements, however, the annular diameter during systole or diastole was smaller. In patients with mitral regurgitation requiring surgery, mitral valve prolapse is the most common cause. Annular ring dilatation and chordae tendineae rupture appear to contribute substantially to incurrence of the mitral regurgitation. The heart weight is increased in the majority of patients with symptomatic mitral valve prolapse but normal, however, in those without symptoms. The most frequent complication of mitral valve prolapse is mitral regurgitation with or without congestive heart failure. Patients with redundant leaflets may be at high risk of sudden death. Young women with abnormal resting ECG, prolonged Q-T interval, family history of sudden death or complex ventricular arrhythmias may also be at a greater risk of sudden death. The incidence of infective endocarditis appears higher in those with redundant than in those with nonredundant valves. The incidence of cerebral ischemic events is low.(ABSTRACT TRUNCATED AT 400 WORDS)