Exercise testing in aortic regurgitation: Comparison of radionuclide left ventricular ejection fraction with exercise performance at the anaerobic threshold and peak exercise

Abstract

Serial radionuclide left ventricular ejection fractions (EF) were measured during graded supine exercise in 16 control patients and 35 asymptomatic or minimally symptomatic patients with severe aortic regurgitation (AR). Simultaneous pulmonary gas exchange analysis permitted determination of the anaerobic threshold, which is the point during exercise at which lactic acid begins to accumulate in the blood. The EF and oxygen uptake were measured at rest, anaerobic threshold and peak exercise. The mean EF (±1 standard deviation) in control patients increased from 0.65 ± 0.06 at rest to 0.73 ± 0.05 at anaerobic threshold (p < 0.01). No further change in EF occurred between anaerobic threshold and peak exercise (0.73 ± 0.09). Peak oxygen uptake in control patients was 20 ± 4 ml/ kg/min. Patients with AR were classified into 2 groups based on a peak oxygen uptake >16 ml/ kg/min (Group I, n = 26) and < 16 ml/kg/min (Group II, n = 9). In Group I the mean oxygen uptake at the anaerobic threshold and peak exercise was similar to or greater than that in control patients, whereas in Group II patients it was less than in control pa- tients. In Group I, the mean rest EF (0.62 ± 0.07) was similar to that in control patients; there was no change at the anaerobic threshold (0.61 ± 0.10), and then it decreased at peak exercise (0.57 ± 0.12, p < 0.05). In Group II, the mean rest EF (0.44 ± 0.12) was below that in control patients (p < 0.01); there was a decrease at the anaerobic threshold (0.35 ± 0.10, p < 0.01), and then it decreased further at peak exercise (0.30 ±0 0.09, p < 0.05). The anaerobic threshold and peak oxygen uptake reflect rest and exercise left ventricular EF in AR and may provide an additional approach of assessing cardiac performance in these patients. Exercise-induced changes in left ventricular EF should be based on the changes occurring before the anaerobic threshold, because changes between anaerobic threshold and peak exercise are of uncertain diagnostic value.