The importance of contractile reserve in predicting exercise tolerance in asymptomatic patients with severe aortic stenosis

Abstract

Background Mortality dramatically rises with the onset of symptoms in patients with severe aortic stenosis (AS). Surgery is indicated when symptoms become apparent or when there is ventricular decompensation. Cardiopulmonary exercise testing (CPET) in combination with exercise echocardiography can unmask symptoms and provides valuable information regarding contractile reserve. The aim of the present study was to determine the prevalence of reduced exercise tolerance and the parameters predicting adverse cardiovascular events. Methods Thirty-two patients with asymptomatic severe AS were included in this study. Patients were followed up as part of an enhanced surveillance clinic. Results Age was 69 ± 15.7 years, 75% of patients were male. Patients had a raised NT-ProBNP of 301 pg/mL. VO2peak was 19.5 ± 6.2 mL/kg/min. Forty-one percent of patients had a reduced %VO2peak and this predicted unplanned cardiac hospitalisation (P = 0.005). Exercise systolic longitudinal velocity (S′) and age were the strongest independent predictors for VO2peak (R 2 = 0.76; P < 0.0001). Exercise S′ was the strongest independent predictor for NT-ProBNP (R 2 = 0.48; P = 0.001). Conclusion A large proportion of patients had a lower than predicted VO2peak. The major determinant of exercise and NT-ProBNP is the ability of the left ventricle (LV) to augment S′ on exercise rather than the severity of aortic valve obstruction or resting structural remodelling of the LV. Reduced exercise tolerance and more adverse remodelling, rather than valve obstruction predicted unplanned hospitalisation. This study demonstrates that for those patients, in whom a watchful waiting is an agreed strategy, a detailed assessment should be undertaken including CPET, exercise echocardiography and biomarkers to ensure those with exercise limitation and risk of decompensation are detected early and treated appropriately.