Epidemiological studies suggest that low heart rate is associated with decreased cardiovascular and all-cause mortality. Heart rate has been reported to be an independent predictor for outcome after myocardial infarction. Pharmacological interventions that reduce heart rate, using drugs such as ß-blockers and calcium channel blockers, generally reduce mortality and improve outcome. In the animal kingdom, an inverse relationship has been observed between heart rate and life expectancy, and the apparent explanation is that heart rate is a marker for metabolic rate and energetic requirements. In hibernating animals, the fall in metabolic rate is achieved by a drop in body temperature and heart rate. Thus, the concept can be read as the less the energy needed, the longer the life span...