Heart rate response and functional capacity in patients with chronic heart failure with preserved ejection fraction

AimsThe mechanisms of exercise intolerance in heart failure with preserved ejection fraction (HFpEF) are not yet elucidated. Chronotropic incompetence has emerged as a potential mechanism. We aimed to evaluate whether heart rate (HR) response to exercise is associated to functional capacity in patients with symptomatic HFpEF. Methods and resultsWe prospectively studied 74 HFpEF patients [35.1% New York Heart Association Class III, 53% female, age (meanstandard deviation) 72.5 +/- 9.1years, and 59.5% atrial fibrillation]. Functional performance was assessed by peak oxygen consumption (peak VO2). The mean (standard deviation) peak VO2 was 10 +/- 2.8mL/min/kg. The following chronotropic parameters were calculated: Delta-HR (HR at peak exercise-HR at rest), chronotropic index (CI)=(HR at peak exercise-resting HR)/[(220-age)-resting HR], and CI according to the equation developed by Keteyian et al. (CIK) (HR at peak exercise-HR at rest)/[119+(HR at rest/2)-(age/2)-5-HR at rest]. In a bivariate setting, peak VO2 was positively and significantly correlated with Delta-HR (r=0.35, P=0.003), CI (r=0.27, P=0.022), CIK (r=0.28, P=0.018), and borderline with HR at peak exercise (r=0.22, P=0.055). In a multivariable linear regression analysis that included clinical, analytical, echocardiographic, and functional capacity covariates, the chronotropic parameters were positively associated with peak VO2. We found a linear relationship between Delta-HR and peak VO2 ( coefficient of 0.03; 95% confidence interval: 0.004-0.05; P=0.030); conversely, the association among CIs and peak VO2 was exponentially shaped. ConclusionsIn patients with chronic HFpEF, the HR response to exercise was positively associated to patient's functional capacity.