Role of heart rate in coronary artery disease
Heart rate: a predictor of morbidity and mortality
A significant association between resting heart rate and cardiovascular mortality has been reported in numerous epidemiological studies over the last 25 years,10,11 both in the general population12 and in those with various cardiovascular diseases, including hypertension, coronary artery disease, and heart failure.
A study in 5713 men without known or suspected cardiovascular disease, followed up for 23 years, demonstrates that all-cause mortality, nonsudden and sudden cardiac deaths, increase progressively with increasing heart rate and this remains significant after adjustment for other factors like age, diabetes, systolic arterial pressure, body mass index, and level of physical activity.13
Another study involving 24 913 men and women with suspected or proven coronary artery disease who were followed up for 14.7 years has also demonstrated that both all-cause mortality and cardiovascular mortality are directly and independently related to resting heart rate at study admission (Figure 1).14 Patients with resting heart rates of 83 bpm or above are at a significantly elevated risk of total and cardiovascular mortality after adjustment for other clinical variables.
Figure 1. Heart rate and mortality after adjustment for age, gender, hypertension, diabetes
mellitus, cigarette smoking, clinically significant coronary artery disease, recreational
activity, treatment with antiplatelets, diuretics, β-blockers, and lipid-lowering drugs.14
In coronary artery disease, increased heart rate can also predispose to plaque rupture,15 which can trigger the acute coronary events that are linked to mortality. Heart rate is also directly associated with the progression of coronary atherosclerosis.16 Reducing heart rate could have a positive impact on prognosis in patients with various cardiovascular diseases. In 11 placebo-controlled trials involving more than 16 000 patients after myocardial infarction (MI), a significant association was found between the β-blocker–induced reduction in heart rate and reduction in mortality.17
Similar results have also been observed in other trials in post-MI patients.18 Another recent meta-analysis of 14 trials involving post-MI patients demonstrates a statistically significant relationship between heart rate reduction and cardiac death (P=0.02), sudden death (P<0.01), and reinfarction (P<0.01). Each 10 bpm reduction in the heart rate is estimated to reduce cardiac death by about 30% (Figure 2).19
Figure 2. Meta-regression: heart rate reduction and reduction in cardiac death in post-MI patients.19
Even in patients with heart failure, there is a relation between reduction in heart rate and mortality (Figure 3).20 Recent studies in heart failure have also shown that heart rate reduction was the most powerful predictor of survival in multivariate analysis. The best prognosis was observed in patients with the lowest baseline heart rate and with the greatest heart rate reduction.21,22
Figure 3. Mortality in patients with heart failure with a variety of drug regimens in different trials and its relation to heart rate.20
Thus, reducing heart rate can prevent ischemic episodes and can also have a positive impact on prognosis.
This benefit of pure heart rate reduction has been demonstrated in the BEAUTIFUL study, which also shows new evidence that stable coronary patients with a resting heart rate >70 bpm have a higher risk of cardiovascular events.24
References
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