Background: Both impaired heart rate recovery (HRR) and low fitness are associated with higher mortality risk. In addition, HRR is influenced by fitness status. The interaction between HRR, mortality, and fitness has not been clearly defined. Thus, we sought to evaluate the association between HRR and all-cause mortality and to assess the effects of fitness on this association.
Methods: Treadmill exercise testing was performed in 5974 male veterans for clinical reasons at two Veterans Affairs Medical Centers (Washington, DC and Palo Alto, CA). HRR was calculated at 1 and 2 min of recovery. All-cause mortality was determined over a mean 6.2-year follow-up period.
Results: Mortality risk was significantly and inversely associated with HRR, only at 2 min. A cut-off value of 14 beats/min at 2 min recovery was the strongest predictor of mortality for the cohort (hazard ratio = 2.4; CI 1.6-3.5). The mortality risk was overestimated when exercise capacity was not considered. When both low fitness and low HRR were present (≤6 metabolic equivalents and ≤14 beats/min), mortality risk was approximately seven-fold higher compared to the High-fit + High-HRR group (>6 metabolic equivalents and >14 beats/min).
Conclusions: HRR at 2 min post exercise is strongly and inversely associated with all-cause mortality. Exercise capacity affects HRR-associated mortality substantially and should be considered when applying HRR to estimate mortality.