Cardiac response to exercise in patients with chronic aortic regurgitation.

Rest and exercise measurements of left ventricular (LV) ejection fraction (EF) and volumes were obtained by radionuclide angiocardiography (RNV) in 30 patients with severe aortic regurgitation (AR). The ratio of peak systolic pressure to end-systolic volume was used as an index of contractility. Volumetric cardiac output (CO) averaged 11.7 +/- 3.8 L/min at rest and 18.4 +/- 5.6 L/min during exercise. Much individual variation occurred in LVEF and end-diastolic volume (EDV) responses to exercise, and there was no consistent change in these measurements. Resting hemodynamic parameters and clinical history correlated poorly with changes observed during exercise. An increase in heart rate was one mechanism used by all 30 patients to increase CO during exercise. An inverse relationship was defined between the change in myocardial contractility and the change in EDV during exercise. Patients with the greatest increase in contractility during exercise showed the greatest decrease in EDV. Less use of an exercise increase in contractility was associated with an exercise increase in EDV to meet the demand for greater CO. Therefore, exercise measurements of LV function provide unique information regarding the degree of impairment of the LV myocardium in these patients with chronic AR.