Long-term effects of cardiac rehabilitation on end-exercise heart rate recovery after myocardial infarction.

Background: Heart rate recovery (HRR) is a marker of vagal tone that is a powerful predictor of mortality in patients with coronary artery disease.
Design: This study aims at evaluating the effects of long-term exercise training on HRR after acute myocardial infarction (AMI), in order to clarify whether prolonged exercise training could maintain a long-term improvement of HRR.
Methods: Forty-four patients after AMI were enrolled in a 3-month hospital-based exercise training programme. At the end, patients were subdivided into two groups: group A (n=22), patients discharged with a specific home-based exercise training programme and instructions for improving leisure-time physical activity; group B (n=22), patients discharged with generic instructions to maintain physical activity. All patients underwent a cardiopulmonary exercise test before, at the end of 3 months exercise training and at 6 months follow-up.
Results: At the end of the hospital-based exercise training programme we observed an increase in peak oxygen consumption [VO2peak; from 13.9+/-3.6 to 18+/-2.7 ml/kg per min (A) and from 14.1+/-3.9 to 17.9+/-2.1 ml/kg per min (B), P<0.001] and in HRR [from 17.1+/-1.8 to 23.4+/-1.4 beats/min (A), and from 18.8+/-2.1 to 24.3+/-1.9 beats/min (B), P<0.001]. At 6 months' follow-up we observed a further improvement in VO2peak (from 18.0+/-2.7 to 20.3+/-2.7 ml/kg per min, P<0.001) and in HRR (from 23.4+/-1.4 to 27.8+/-2.1 beats/min, P<0.001) in group A, but a significant decrease in VO2peak and in HRR in group B (P<0.001).
Conclusion: Long-term exercise training is useful for maintaining or improving the beneficial results of the standard 3-month exercise training programme on cardiovascular capacity and HRR. This observation may bear beneficial prognostic effects on patients after AMI.