Exercise training enhances autonomic function after acute myocardial infarction: a randomized controlled study

Introduction: Heart rate recovery, defined as the fall in heart rate during the first minute after exercise, is an indicator of autonomic function, and has been found to be an independent predictor of mortality after acute myocardial infarction. Exercise training has several well-known benefits in terms of cardiorespiratory fitness, modifiable cardiovascular risk factors and prognosis after acute coronary events. However, there are no randomized controlled studies in the literature evaluating the effects of exercise training per se, controlling for changes in medication and diet, on heart rate recovery. Thus, this study aims to assess the effects of exercise training on autonomic function in coronary artery disease patients recovering from acute myocardial infarction.

Methods: Thirty-eight patients following a first acute myocardial infarction participated in this prospective randomized clinical trial. Patients were randomized into two groups: exercise training or control. The exercise group participated in an 8-week aerobic exercise program, while the control received standard medical care and follow-up. Changes in hemodynamics at rest and at peak exercise (heart rate, systolic and diastolic blood pressure, and rate pressure product), dietary intake, cardiorespiratory fitness, and heart rate recovery were assessed.

Results: Medication and diet remained unchanged in both groups during the study period. The exercise-training group improved resting hemodynamics, particularly resting heart rate (from 68.0 ± 9.2 to 62.6 ± 8.7 bpm, p=0.030) and systolic blood pressure (from 135 ± 7.1 to 125.6 ± 11.3 mm Hg, p=0.012), cardiorespiratory fitness (from 30.8 ± 7.8 to 33.9 ± 8.3 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 diet or medication.