Objectives: To assess the physiological changes that take place in patients with coronary artery disease after 6 and 18 months of moderate-intensity endurance training.
Design: Prospective non-randomised controlled study.
Setting: Johannesburg Cardiac Rehabilitation Centre, a community-based phase III cardiac rehabilitation programme.
Subjects: The 93 patients who completed 18 months of training form the experimental or 'complier' group, while the 18 patients who discontinued the programme form the comparison or 'dropout' group.
Outcome measures: Haemodynamic, electrocardiographic and metabolic measurements at rest and at submaximal and peak exercise levels on admission and after 6 and 18 months of endurance training.
Results: Among the compliers several significant changes took place. Resting heart rate and blood pressure decreased at 6 months (P < 0.005). Submaximal heart rate, blood pressure, rate-pressure product and ventilation decreased at 6 months (P < 0.0001, P < 0.01, P < 0.001, P < 0.01 respectively), and the rate-pressure product decreased further at 18 months (P < 0.05). Ventilatory threshold increased at 6 months (P < 0.0001). Peak oxygen uptake, heart rate and ventilation increased at 6 months (P < 0.0001, P < 0.005 and P < 0.0001, respectively), with no further changes at 18 months. Treadmill time increased at 6 months and again at 18 months (P < 0.0001). The only significant change in the dropout group was an increase in ST-segment depression on the exercise ECG from 0.2 to 0.6 mm (P < 0.05).
Conclusion: The study confirms that cardiac rehabilitation is beneficial. Most changes occurred in the first 6 months, the longer period of 18 months serving mostly as reinforcement of these and other lifestyle changes.