Haemodynamic adaptation to exercise in asymptomatic patients with severe aortic regurgitation.

Thirty-six patients with severe aortic regurgitation and 10 normal subjects underwent radionuclide angiography to examine the cardiovascular adaptations to exercise. Patients were sub-divided into four groups based on the directional change of ejection fraction with exercise. Group A (15 patients) showed normal ejection fraction at rest and peak exercise (0.65 +/- 0.05 and 0.73 +/- 0.06 respectively). Group D (six patients) showed significant abnormalities in left ventricular function at rest with further deterioration during exercise (0.44 +/- 0.09 to 0.35 +/- 0.07 respectively). In patients with good left ventricular function left ventricular end-diastolic and end-systolic volume decreased progressively with exercise and at peak exercise end-systolic volume was within normal limits. In patients with poor left ventricular function both end-diastoic and end-systolic volume progressively increased with exercise. Both net and total stroke volume were significantly higher at rest in patients with normal left ventricular function but net stroke volume increased with exercise only in those with good myocardial function and was quantitatively similar to that seen in normal subjects. The severity of aortic regurgitation as judged by regurgitant fraction was reduced during exercise in all except four patients, by an average of 22% in all groups. The major factor determining increasing cardiac output with exercise was found to be the status of myocardial function. Although reduction in the severity of aortic regurgitation may favourably influence distribution of stroke volume in those with normal myocardial function, it failed to contribute significantly to increasing cardiac output in those with poor left ventricular function.