Abnormal heart rate recovery after symptom-limited exercise has been found to be a predictor of mortality in intermediate-risk patients. Whether such a finding portends an increased risk of death in other populations is unknown. Cole and associates examined whether heart rate recovery following sub-maximal stress testing is a predictor of long-term mortality in adults without evidence of cardiovascular disease.
The study included 5,234 participants in the Lipid Research Clinics Prevalence Study, a large multicenter study of the prevalence of lipid abnormalities among North Americans. The participants were selected from the group of 8,681 persons who underwent exercise testing using the Bruce or modified Bruce protocol. None had evidence of cardiovascular disease. Heart rate recovery was defined as the change from the peak heart rate to the heart rate after two minutes of recovery. An abnormal heart rate recovery was calculated to be 42 beats per minute or less. The primary end point in the study was all-cause mortality as determined by telephone interviews with the study participants or their families or employers. Mean follow-up was 12 years.
The median value for heart rate recovery was 49 beats per minute. Heart rate recovery was abnormal (i.e., 42 beats per minute or less) in 1,715 (32.8 percent) of the 5,234 participants. Death occurred in 325 (6.2 percent) of the 5,234 patients during the 12 years of follow-up. Abnormal heart rate recovery was strongly predictive of death (10 percent compared with 4 percent in participants with a normal heart rate recovery; relative risk, 2.58). Abnormal heart rate recovery remained predictive of death after adjustment for risk factors, fitness, and resting and exercise heart rates. The adjusted relative risk of death was 1.55. Of the participants who died, 116 (35.7 percent) were thought to have died of cardiovascular causes. Abnormal heart rate recovery was even more strongly predictive of death from cardiovascular disease than of death in general (4 percent compared with 1 percent; relative risk, 3.06).
The authors conclude that heart rate recovery after submaximal exercise may be a clinically relevant predictor of mortality, especially cardiovascular mortality. On the basis of their findings, the authors suggest that consideration be given to incorporating heart rate recovery into the interpretation of exercise stress testing.