Effects of Exercise on Left Ventricular Volume and Output Changes in Severe Mitral Regurgitation: A Radionuclide Angiographic Study

Abstract

Symptom-limited supine bicycle exercise with radionuclide angiography was performed on 11 patients with severe mitral regurgitation (who were not receiving vasodilators), to assess changes in left ventricular volume, regurgitant fraction, forward flow and regurgitant flow during exercise. All patients were in normal sinus rhythm with a normal resting ejection fraction (greater than 0.50). During exercise, the end-diastolic volume index, end-systolic volume index, ejection fraction, and regurgitant fraction of the left ventricle did not change significantly. The forward cardiac index increased by 86 percent (p less than 0.01) with exercise. This increase was explained by an 87 percent increase in the heart rate (p less than 0.01); there was no significant change in the forward stroke volume index. Although the regurgitant stroke volume index declined by 12 percent with exercise (p = 0.07), the regurgitant flow increased markedly by 64 percent (p less than 0.01) to a mean of 8.2 L/min/m2. These data indicate that in patients with severe mitral regurgitation, the increase in the exercise forward flow is totally dependent on the heart rate response. There is a marked increase in regurgitant flow during exercise, which presumably contributes to dyspnea.