Echocardiographic predictors of exercise intolerance in patients with heart failure with severely reduced ejection fraction

Decreased exercise capacity (EC) is an established predictor of cardiac and all-cause mortality in patients with chronic heart failure (HF). No correlation has been found between EC and left ventricular (LV) ejection fraction. Moreover, data about the effect of right ventricular (RV) function on EC in HF with severe LV dysfunction are limited and contradictory. In this study, we aimed to investigate the relationship between EC and myocardial mechanics in patients with HF with reduced ejection fraction. Consecutive patients with symptomatic HF and LV ejection fraction ≤35% were prospectively assessed. All patients were evaluated with enhanced echocardiography. A symptom-limited treadmill cardiopulmonary exercise test (CPX) was performed within 24-hour interval. Patients were stratified into 4 groups according to their EC defined by Weber's classification. Prognosis of EC, expressed as oxygen uptake at peak exercise (peak VO(2)), was evaluated in multivariate linear regression analysis model. Sixty-seven patients with New York Heart Association classes II to III and a mean LV ejection fraction of 26 ± 7% were enrolled. A wide range of peak VO(2) was observed in CPX with patient exercise performance distributed to all classes according to Weber's classification. Significant differences were found in RV systolic and diastolic functions between groups with different classes of EC: RV peak systolic myocardial velocity (S′) (P < .001), tricuspid annular plane systolic excursion (TAPSE) (P = .003), RV E’ (P = .003). In patients with functional decline, systolic pulmonary artery pressure (PASP) was higher (P = .029) and TAPSE/PASP ratio was lower (P = .006). No significant differences were found in LV diameter, systolic and diastolic function, and degree of mitral regurgitation. Thirty three patients with RV systolic dysfunction showed lower peak VO(2) and oxygen uptake at anaerobic threshold (P = .008, P = .006, respectively), shorter exercise time (P = .003), and lower systolic blood pressure (P = .01) than in patients with normal RV systolic function. Logistic multivariate linear regression analysis with stepwise inclusion and exclusion revealed that gender, RV S′, and RV free wall strain were independent predictors of peak VO(2). RV function, assessed as S′ and free wall strain, was independently related to EC, measured using CPX, in patients with HF and severe LV systolic dysfunction.