Angiographic studies demonstrating alterations in left ventricular contraction have been cited as evidence that isolated mitral valve prolapse (MVP) may be associated with a cardiomyopathy. We studied 17 patients with isolated MVP undergoing cardiac catheterization who had chest pain, palpitations, and/or a murmur of mitral regurgitation. Eleven of 13 patients (85%) with no or mild (Grade 1+) mitral regurgitation had normal left ventricular hemodynamic measurements, while three of four patients (75%) with moderate or marked (Grades 2+-4+) regurgitation had abnormal left ventricular hemodynamic measurements. An increased mean rate of circumferential fiber shortening (greater than 1.9 circumferences/sec) was observed in nine of 13 patients (70%). Systolic ventricular wall motion was analyzed from left ventriculograms by methods which quantitate percent shortening of ventricular areas, transverse chords, and radial axes. Marked variations in the number and location of alterations in ventricular contraction were obtained by the different methods used to analyze the ventriculograms, with segments of hypokinesis being detected in from 0-14 patients studied, depending upon the method used. Localization of alterations in contraction predominantly in the basal and mid-segments of the left ventricular and the association of hemodynamic abnormalities with mitral regurgitation suggest that changes in ventricular contraction are primarily related to an alteration of mitral valve function in this condition.