PALO ALTO, CALIFORNIA. Several studies have shown that people whose heart rate quickly returns to normal after exercise have a lower risk of dying from heart disease than do people whose heart rates remain elevated for longer. Researchers at two Veterans Affairs Medical Centers now report that heart rate recovery measurements can also be used to predict the presence of coronary artery disease (CAD). Their study involved 2193 male patients who had undergone treadmill testing and within 3 months had been examined with coronary angiography because of chest pain. The patients were followed for an average of 7 years to determine mortality and the presence of CAD.
The study participants underwent symptom-limited treadmill testing involving small, frequent increments in workload rather than abrupt increases every 3 minutes. The test was designed so that patients would reach 85% of their maximum physiologic heart rate within 10 minutes. Maximum heart rate was calculated as 220 minus age. Patients were placed in the supine position immediately after completion of the treadmill test and their heart rate measured at 1, 2, 3 and 5 minutes.
The researchers found that patients on beta-blockers were much less likely to achieve 85% of their
maximum heart rate. Only 14.2% of the 744 patients on beta-blockers did so as compared to 42.6% of
those not on beta-blockers. They also observed that patients with a decrease of less than 22 beats during
the second minute of recovery had significantly more extensive CAD than did those whose decrease
exceeded 22 beats/minute. A similar pattern was observed in regard to overall mortality. The researchers
conclude that heart rate recovery during the first 2 minutes after cessation of exercise can be used to predict
mortality and the presence of CAD. They believe that the slower recovery is an indication of a slower
reactivation of the vagal (parasympathetic) branch of the autonomic nervous system after exercise.