Abstract
Background Exercise-induced high heart rate may impair exercise tolerance by reducing diastolic filling time and ventricular filling in heart failure with preserved ejection fraction (HFpEF). Given the importance of chronotropic response, we hypothesized that reduction in diastolic filling time because of exercise-induced increased heart rate would not impair cardiac output reserve and exercise capacity. We sought to determine the association between heart rate, diastolic filling time, hemodynamics, and exercise capacity in HFpEF. Methods and Results Patients with HFpEF (n=66) and controls without HF (n=107) underwent bicycle exercise echocardiography with simultaneous expired gas analysis to measure oxygen consumption. Diastolic filling time was assessed by the overlap time between mitral E- and A-waves (longer overlap time indicates shorter diastolic filling duration). Overlap time increased (ie, diastolic filling time shortened) in HFpEF and controls as heart rate increased with exercise, and the relationship was similar between the groups. Greater heart rate response correlated with higher cardiac output (r=0.51, P<0.0001) and oxygen consumption (r=0.50, P<0.0001) during peak exercise. Shorter diastolic filling time, as assessed by longer overlap time, was correlated with higher cardiac output (r=0.47, P<0.0001) and peak oxygen consumption (r=0.38, P=0.007), not with E/e' or right ventricular-pulmonary artery uncoupling. Longer overlap time was associated with mitral A velocity (r=0.53, P<0.0001) and left atrial booster pump strain (r=0.42, P<0.0001). Conclusions Shortening of diastolic filling interval in tandem with increased heart rate during exercise does not limit cardiac output reserve or exercise capacity in HFpEF.