The correlates of an abnormal first heart sound in mitral-valve-prolapse syndromes.

In 52 patients with mitral-valve prolapse we studied the intensity of the first heart sound (S1) in relation to the timing of the prolapse and to the presence of leaflet tip coaptation. Sixteen normal subjects served as controls. With two-dimensional echocardiography, three distinct groups were identified. Sixteen patients had early systolic mitral prolapse coincident with initial mitral-leaflet coaptation at the S wave on electrocardiography. Twenty-one had middle to late systolic mitral prolapse. Fifteen had flail mitral leaflet without normal leaflet coaptation at the free margins. The intensity of S1 was expressed as the ratio of the S1 amplitude to that of the aortic component of the second heart sound. This ratio was greater in the patients with early prolapse (6.2 +/- 3.1, mean +/- S.D.) than in the controls (1.4 +/- 0.7) (P less than 0.01). The ratio was reduced in patients with flail valves (0.3 +/- 0.5) (P less than 0.01) and did not differ between patients with middle to late prolapse (1.3 +/- 0.6) and controls. We conclude that the amplitude of S1 may provide a clue to the type and timing of mitral-valve prolapse.