The effect of rest and physical effort on the left ventricular burden in mitral and aortic regurgitation

Abstract

To clarify the different natural histories of mitral and aortic regurgitation, the effect of rest on the left ventricular burden was studied in 5 patients, each with mitral or aortic regurgitation (moderate to severe, functional Class II) and no other significant lesions. Forward and regurgitant flows were measured by upstream and downstream dye dilution with continuous infusions of indocyanine-green dye during supine exercise and at rest. In mitral regurgitation, the regurgitant fractions at exercise and rest did not differ; but all flows fell with rest, with striking reduction in total left ventricular work and flow per minute and per beat. However, in aortic regurgitation, regurgitant fraction increased with rest, fall in forward flow was balanced by rise in regurgitant flow, total flow and work/minute were unchanged, and total stroke volume and stroke work increased substantially. The differences between the two lesions in response to rest were statistically significant. Thus, patients with mitral regurgitation can, but patients with aortic regurgitation cannot, moderate their hemodynamic burden by restricting activity.