High heart rate: a cardiovascular risk factor?

De battre mon coeur s'est arrete—Movie by Jacques Audiard. Resting heart rate (RHR) is one of the simplest cardiovascular parameters, which usually averages 60 to 80 beats per minute (b.p.m.), but can occasionally exceed 100 b.p.m. in unconditioned, sedentary individuals and be as low as 30 b.p.m. in highly trained endurance athletes. Epidemiological evidences demonstrate that RHR, or its corollaries, namely post-exercise heart rate recovery, which is mediated primarily by vagal tone, and heart rate variability (HRV, beat-to-beat variability also mediated by autonomic nervous system, especially parasympathetic) correlates with cardiovascular morbidity and suggests that RHR determines life expectancy. Multiple studies have identified RHR as an independent risk factor for cardiovascular disease (comparable with smoking, dyslipidemia or hypertension). However, it is often overlooked. Since 1980, it is known that resting heart rate (RHR) is a prognostic factor in coronary diseased patients.1,2 Data from the Coronary Artery Surgery Study (CASS) published last year underline the prognostic importance of RHR for morbidity (time to rehospitalization), as well as total and cardiovascular mortality.3 Heart rate proves to be the best predictor after myocardial infarction,4,5 in patients with congestive heart failure, as well as in patients with diabetes mellitus or hypertension. In addition, it was found that elevated RHR is also strongly associated with mortality in the general population. For instance, in the Framingham Study, in a cohort composed of 5070 subjects who were free from cardiovascular disease at the time of entry into the study, cardiovascular and coronary mortality increased progressively with RHR6 ( Figure 1 ). In a subset of 4530 untreated hypertensive (>140 mmHg systolic or >90 mmHg diastolic) patients included in this study, using 36-year follow-up data, odds ratio (OR) for each increment in heart rate of 40 b.p.m. were 1.68–1.70 (CI: 1.08–2.67) for cardiovascular mortality and fascinatingly also 2.14–2.18 … *Corresponding author. Tel: +41 31 632 96 53; fax: +41 31 632 47 71. E-mail address : otto.hess{at}insel.ch