Abnormal left ventricular contraction pattern in the systolic click-late systolic murmur syndrome.

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Abstract
A contraction abnormality of the left ventricle has previously been described in patients with systolic click-late systolic murmur syndrome. To determine if the contraction abnormality is present in the preprolapse period, LV dimensions and the instantaneous velocity of circumferential fiber shortening (VCF) were studied in 18 patients with the mitral valve prolapse and 16 normal subjects using computer analysis of echocardiograms. VCF attained its maximum (max VCF) during the preprolapse period an average of 94 msec before the mid-systolic click. Max VCF was significantly reduced in patients with mitral valve prolapse (2.06 vs 2.55 circ/sec in normal subjects, P less than 0.001). Despite the reduction in max VCF, no difference in the extent and percentage of diameter shortening was found between patients and normal subjects. This discrepancy is explained by a sustained rate of mid-to-late systolic diameter shortening in the presence of mitral valve prolapse as manifested by a typical VCF profile (P less than 0.001) and a longer duration of diameter shortening (353 vs 306 msec in normal subjects, P less than 0.01). The decrease of max VCF in patients with mitral valve prolapse suggests a reduction in LV contractility. Since the abnormality is present in the preprolapse period, it is unrelated to a direct mechanical effect of the prolapse itself. Additional fiber shortening in mid-to-late systole indicates that the sudden displacement of the mitral leaflets may have an unloading effect on the left ventricle.