HEART RATE PROFILE DURING EXERCISE
It can be predictive of sudden death.
The heart rate profile during exercise and recovery could serve as a predictor of sudden death in patients without known heart disease.
From 1967 to 1972, 5,713 42-to-53-year-old men having no heart disease symptoms were examined. The patients' heart rates at rest, the increase in the rate at rest to that at the peak exercise level, and the decrease in the rate from the peak exercise level to that one minute after the termination of exercise were measured. Patients also received baseline electrocardiographic and physical examinations, had blood work performed, and answered questionnaires concerning medical history, level of physical activity, use of tobacco, presence of diabetes, and parental history of sudden death or myocardial infarction. Patients who had systolic blood pressures higher than 180 mmHg or abnormal heart rates or rhythms at rest were excluded from the study.
Bicycle exercise tests consisting of three successive workloads were conducted and the patient's cardiac rhythm continuously monitored. The heart rate was measured at rest, every two minutes during exercise at peak performance, and every minute for 10 minutes after exercise ended. If the patient suffered fatigue, leg cramps, or chest pain, if the systolic blood pressure exceeded 250 mmHg or the heart rate 180 beats per minute, or if either ventricular tachycardia or ischemic electrocardiographic changes occurred, the test was terminated.
In the 23 years during which patients were followed, 1,516 deaths occurred, including 400 attributable to cardiac causes (7% of study subjects), of which 81 were sudden deaths and 129 were nonsudden deaths from myocardial infarction (MI). The mean interval between the initial clinical examination and sudden death was 11.7 years, and in nonsudden death, 16.8 years.
It was found that among patients who had a resting heart rate of more than 75 beats per minute, an increase in heart rate during exercise of less than 89 beats per minute, or a decrease in heart rate of less than 25 beats per minute after the termination of exercise, there was a greater risk of sudden death from MI.
The finding may prove useful to clinicians performing physical examinations of physically active patients, who might be asked whether they know their peak exercise and recovery heart rates and the intervals to recovery--if a patient falls into one of the categories cited above, heart disease may be suspected. Further, health care practitioners should educate all physically active patients in the monitoring of resting, peak exercise, and recovery heart rates.-PWF
Jouven X, et al. N Eng J Med 2005; 352(19):1951-8.