Significance of reduction in heart rate in cardiovascular disease.

Epidemiologic studies suggest that lower heart rate is associated with decreased cardiovascular and all-cause mortality. Heart rate has also been reported to be an independent predictor of outcome after myocardial infarction (MI). Because it is a major determinant of oxygen consumption and metabolic demand, a decrease in heart rate would be expected to decrease cardiac workload. Among patients with restricted coronary blood flow, increased heart rate is associated with more severe myocardial ischemia, angina, and an increase in size of MI. Pharmacologic interventions that reduce heart rate, such as beta blockers, generally reduce mortality and improve outcome. A number of clinical trials using beta blockers after MI has shown a relationship between reduction in heart rate and reduction in mortality. Most beta blockers demonstrate a nearly linear relationship between reductions in mortality and in heart rate. The evidence from trials with calcium antagonists is more equivocal, possibly because until very recently none were available that decreased heart rate without decreasing myocardial contractility. Drugs that do not reduce the heart rate after an MI and in congestive heart failure have not been found to improve survival. In light of the findings thus far reported, reduction in heart rate should be a therapeutic goal in the treatment of cardiovascular disease.