Heart rate response and recovery in cycle exercise testing: normal values and association with mortality

Chronotropic incompetence and impaired heart rate (HR) recovery are related to mortality. Guidelines lack specific reference values for HR recovery. We defined normal values and studied blunted HR response and recovery and mortality risk.

We included 9917 subjects (45% females) aged 18–85 years who performed a cycle exercise test. We defined normal values for peak HR, HR reserve, and HR recovery at 1 and 2 min (HRR₁ and HRR₂) based on individuals apparently healthy (N = 2242). Associations between blunted HR indices (<5th percentile) and mortality over a median follow-up of 8.6 years were analysed using Cox regression and competing risk analysis. All HR indices were age-dependent and independent predictors of all-cause and cardiovascular (CV) mortality. The 5th percentiles of HR reserve, HRR₁, and HRR₂ correlated weakly with existing reference values. Heart rate recovery variables were the strongest predictors of all-cause mortality in both the overall population [HRR₁, hazard ratio 1.70 (95% confidence interval, 1.49–1.94), and HRR₂, 1.57 (1.37–1.79)] and in subjects with normal exercise capacity [HRR₁, 1.96 (1.61–2.39), and HRR₂, 1.76 (1.46–2.12)]. Combining HR indices appeared to increase the risk of all-cause [HRR₁ and HRR₂, 1.96 (1.68–2.29), and peak HR and HRR₁, 1.87 (1.56–2.23)] and CV mortality, although no specific combination was superior for predicting CV mortality.

All HR indices were age-dependent and associated with all-cause and CV mortality. Blunted HR recovery variables were the strongest predictors of all-cause mortality, even in subjects with normal exercise capacity. Combined blunted HR indices appeared to add prognostic value.