Abstract 15692: Resting Heart Rate and Chronotropic Response to Exercise: Prognostic Implications in Heart Failure

Abstract

Background: Higher resting heart rate (HR) and impaired chronotropic response to exercise are both prognostic of adverse outcomes in heart failure (HF). We aimed to study how resting HR and chronotropic response to exercise relate to each other, and to examine their prognostic value in HF patients across the LVEF spectrum. Methods: We studied 892 HF outpatients (mean age 55 years, 68% male, 33% with atrial fibrillation) who underwent maximal cardiopulmonary exercise testing. Chronotropic index (CIx) was calculated as (peak HR – resting HR)/(age-predicted maximal HR – resting HR). Cox proportional hazards models were fit to study the relationship between CIx and resting HR with the composite outcome of LVAD implantation, transplantation, or death (243 events during 4.2±1.9 yr of follow-up). Multivariate models adjusted for age, sex, symptomatic status, cardiomyopathy etiology, COPD, diabetes, atrial fibrillation, LVEF, eGFR, beta-blocker use, and peak VO 2 . Results: Resting HR was 72±14 bpm and CIx was 0.55±0.28. The average LVEF was 33±15%, with 28% with an LVEF ≥45%. 85% of patients were on beta-blockers. Both higher resting HR and lower CIx were associated with higher NYHA class and lower peak VO 2 , but resting HR poorly correlated with CIx (r=0.07; p=0.04). Both higher resting HR (per SD change: adjusted HR 1.26; 95%CI: 1.09-1.46; p=0.002) and CIx (per SD change: adjusted HR 0.63; 95%CI: 0.63-0.89; p=0.001) were independent prognostic markers in adjusted analyses including both measures. Similar findings were noted in analyses restricted to patients with an LVEF ≥45% or with atrial fibrillation. Conclusion: Higher resting HR and lower CIx are both associated with more severe HF, but correlate poorly with each other. Both are predictive of adverse outcomes suggesting that these two HR-related measures provide independent prognostic information.