Exercise Training Improves Autonomic Function After an Acute Myocardial Infarction

Heart rate recovery, defined as the fall in heart rate during the first minute after exercise, is an indicator of autonomic function, which was found to be an independent predictor of mortality after an acute myocardial infarction. PURPOSE: To assess the effects of exercise training on autonomic function, assessed by measuring heart rate recovery at first minute, in coronary artery disease patients recovering from an acute myocardial infarction. METHODS: A single-centre prospective randomized controlled trial was conducted. Forty-seven consecutive patients after the first myocardial infarction were randomized to exercise-training (n=24) or usual medical care (n=23). Complete randomization was performed by allowing patients to choose one of two sealed numbered envelopes. The exercise group participated in an 8-week aerobic exercise program, whereas the control received usual medical care and follow-up. Changes in heart rate and blood pressure at rest and at peak exercise, dietary intake, cardiorespiratory fitness, and heart rate recovery were assessed. RESULTS: Nine patients terminated the study prematurely, leaving thirty-eight for the statistical analysis (exercise-training, n=20, 54.3 ± 10.8 years of age; control group, n=18, 57.0 ± 7.6 years of age). The medication and the dietary intake remained unchanged in both groups during the study period. The exercise-training group improved resting heart rate (from 68.0 ± 9.2 to 62.6 ± 8.7 bpm, P=0.030), resting systolic blood pressure (from 135 ± 7.1 to 125.6 ± 11.3 mmHg, P=0.012), cardiorespiratory fitness (from 31.4 ± 7.7 to 33.7 ± 8.0 ml/min/kg, P=0.016), and heart rate recovery (from 20 ± 6 to 24 ± 5 bpm, P=0.007). No significant changes were observed in the control group. CONCLUSIONS: Exercise training improved autonomic function, assessed by heart rate recovery, resting heart rate and systolic blood pressure, in the absence of changes in dietary intake or medication.