Chronotropic index and long-term outcomes in heart failure with preserved ejection fraction

Little is known about the usefulness of heart rate (HR) response to exercise for risk stratification in heart failure with preserved ejection fraction (HFpEF). Therefore, this study aimed to assess the association between HR response to exercise and the risk of total episodes of worsening heart failure (WHF) in symptomatic stable patients with HFpEF.

This single-center study included 133 patients with HFpEF (NYHA II-III) who performed maximal cardiopulmonary exercise testing. HR response to exercise was evaluated using the chronotropic index (CI_x) formula. A negative binomial regression method was used.

The mean age of the sample was 73.2± 10.5 years; 56.4% were female, and 51.1% were in atrial fibrillation. The median for CI_x was 0.4 [0.3-0.55]. At a median follow-up of 2.4 [1.6-5.3] years, a total of 146 WHF events in 58 patients and 41 (30.8%) deaths were registered. In the whole sample, CI_x was not associated with adverse outcomes (death, P=.319, and WHF events, P=.573). However, we found a differential effect across electrocardiographic rhythms for WHF events (P for interaction=.002). CI_x was inversely and linearly associated with the risk of WHF events in patients with sinus rhythm and was positively and linearly associated with those with atrial fibrillation.

In patients with HFpEF, CI_x was differentially associated with the risk of total WHF events across rhythm status. Lower CI_x emerged as a risk factor for predicting higher risk in patients with sinus rhythm. In contrast, higher CI_x identified a higher risk in those with atrial fibrillation.