Postural exercise abnormalities in symptomatic patients with mitral valve prolapse

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The hemodynamics of the supine and upright exercise response in 16 symptomatic women with mitral valve prolapse (Group I) was compared with that in 8 asymptomatic normal control women (Group II). All subjects had supine and upright echocardiography and phonocardiography at rest and none demonstrated mitral regurgitation. All participants then underwent same day graded bicycle exercise, with simultaneous radionuclide angiography in both the upright and the supine posture. Catecholamines were measured, and a variety of volumetric and hemodynamic data were obtained.Group I (patients with mitral valve prolapse) demonstrated a reduced exercise tolerance, especially during upright exercise, as measured by both total exercise duration and maximal work load achieved. Mean total catecholamine measurements were similar between the two study groups at comparable mean heart rate, mean blood pressure and mean rate-pressure (double) product. No difference was observed in the ratio of right to left ventricular stroke counts at rest or during exercise regardless of posture, suggesting that exercise-induced mitral regurgitation did not occur.A difference was noted, however, in left ventricular end-diastolic volume index. At rest, Group I patients exhibited a 42% decrease in this index when sitting upright, and this difference from supine values persisted at submaximal (300 kpm/min) and peak work loads (34 and 29% difference, respectively). This contrasted with the control subjects whose upright end-diastolic volumes at rest, at 300 kpm/min and at peak exercise were reduced 21, 10 and 3%, respectively, compared with supine values. Cardiac index measurements reflected the reduced left ventricular end-diastolic volume observed. Other measurements, including ejection fraction, left ventricular end-systolic volume index and peak systolic pressure/end-systolic volume ratio, were similar between the two groups at each posture and level of exercise. The percent stroke volume ejected during each third of systolic ejection was also not remarkably different between the groups.In summary, as compared with control subjects, patients with mitral valve prolapse exhibit an exaggerated reduction in left ventricular end-diastolic volume throughout upright exercise. The associated redaction in cardiac output at each level of exercise may contribute to the reduction in exercise tolerance observed in this symptomatic patient subset.