Left and right ventricular function during symptom-limited exercise in patients with isolated mitral stenosis.

Ventricular function during exercise in patients with mitral stenosis has not been widely studied. Accordingly, 20 patients with isolated mitral stenosis were assessed during supine, symptom-limited equilibrium radionuclide ventriculographic studies. All patients had a normal left ventricular (LV) ejection fraction at rest (greater than or equal to 50 percent), and all were in sinus rhythm. Left ventricular ejection fraction rose (p less than 0.001) from 64 +/- 9 percent at rest to 74 +/- 11 percent during exercise. This normal response was due solely to a decrease (p less than 0.01) in exercise LV end-systolic volume. A significant (p less than 0.01) decrease in end-diastolic volume during exercise limited the increase in ejection fraction during exercise. The decrease in end-diastolic volume during exercise caused stroke volume to remain unchanged; cardiac output rose according to heart rate alone. Right ventricular (RV) ejection fraction did not rise with exercise due to an increase in end-systolic volume. With exercise, LV end-diastolic volume was smaller (p less than 0.05) with severe mitral stenosis compared to mild mitral stenosis. With exercise, RV ejection fraction was decreased (p less than 0.05) with severe compared to mild mitral stenosis. In conclusion, LV function during exercise is normal in patients with normal resting LV ejection fraction. A decrease in LV diastolic filling with exercise prevents a rise in stroke volume, and cardiac output increases by heart rate alone. With, exercise, RV ejection fraction does not rise, due to an increase in RV end-systolic volume.