ABSTRACT
Heart rate (HR) at rest has been associated inversely with mortality risk. However, fitness is inversely associated with mortality risk and both increased fitness and ß-blockade therapy affect HR at rest. Thus, both fitness and ß-blockade therapy should be considered when HR at rest-mortality risk association is assessed. From 1986 to 2011, we assessed HR at rest, fitness, and mortality in 18,462 veterans (mean age = 58 ± 11 years) undergoing a stress test. During a median follow-up period of 10 years (211,398 person-years), 5,100 died, at an average annual mortality of 24.1 events/1,000 person-years. After adjusting for age, body mass index, cardiac risk factors, medication, and exercise capacity, we noted approximately 11% increase in risk for each 10 heart beats. To assess the risk in a wide and clinically relevant spectrum, we established 6 HR at rest categories per 10 heart beat intervals ranging from <60 to ≥100 beats. Mortality risk was significantly elevated at a HR at rest of ≥70 beats/min (hazard ratio 1.14, confidence interval 1.04 to 1.25; p <0.006) and increased progressively to 49% (hazard ratio 1.49, confidence interval 1.29 to 1.73; p <0.001) for those with a HR at rest of ≥100 beats/min. Similar trends were noted when for subjects aged <60 and ≥60 years and those treated with ß blockers. In all assessments, mortality risk was consistently overestimated when fitness was not considered. In conclusion, HR at rest-mortality risk association was direct and independent. A progressive increase in risk was noted >70 beats/min for the entire cohort, those treated with ß blockers, and those aged <60 and ≥60 years. Mortality risk was overestimated slightly when fitness status was not considered.
