Systemic and left ventricular responses to exercise stress in asymptomatic patients with valvular aortic stenosis

Patients with heart disease may have myocardial ischemia or left ventricular (LV) dysfunction without symptoms. The exercise responses of 14 asymptomatic patients with valvular aortic stenosis (AS) were studied using treadmill testing, thallium-201 scintigraphy and radionuclide angiography. Compared with age- and gender-matched control subjects, patients with AS demonstrated reduced exercise tolerance (10.7 ± 2.5 vs 13.3 ± 4.2 min; p = 0.06) and maximal oxygen consumption (26.7 ± 6.3 vs 36.3 ± 9.5 ml O₂/min/kg; p = 0.004) associated with decreased peak systolic blood pressure response to exercise (177 ± 18 vs 214 ± 42 mm Hg; p < 0.004). Ten of 14 patients developed ST-segment depression during exercise, only 3 of whom had reversible thallium defects. Patients with AS tended to have greater LV ejection fractions at rest (65 ± 11 vs 58 ± 7; p = 0.08) and significantly decreased early peak filling rates (4.8 ± 1.3 vs 6.1 ± 0.6 stroke volume/s; p = 0.003) compared with those of control subjects. During maximal supine exercise, patients with AS had less of an increase in ejection fraction (2 ± 9 vs 15 ± 7%; p < 0.001) associated with a decrease in end-diastolic (-7 ± 15 vs +5 ± 16%; p = 0.06) and stroke (-6 ± 17 vs +30 ± 13%; p < 0.001) volumes from baseline measurements. The limitation in stroke volume and heart rate to exercise stress in patients with AS was associated with attenuation of the cardiac output response during exercise compared with that of control subjects (73 ± 48 vs 284 ± 48%; p < 0.001), which correlated directly with effort limitation (r = 0.717, p = 0.004). Thus, despite the absence of symptoms patients with AS demonstrate limited effort tolerance with abnormal systemic and LV hemodynamics, which is most likely a consequence of the inability to augment end-diastolic volume during exercise.