Purpose: Exercise-based cardiac rehabilitation has been shown to reduce mortality in patients with coronary artery disease. Although the exact mechanisms by which exercise reduces mortality are unclear, one hypothesis invokes the effect of exercise on autonomic tone. Heart rate recovery (HRR) immediately after exercise is a marker of vagal tone that findings have shown to be a powerful predictor of all-cause mortality. This study aimed to evaluate the effect of exercise-based cardiac rehabilitation on HRR.
Methods: A retrospective study was performed. Patients who completed phase 2 cardiac rehabilitation and had entry and exit exercise stress tests (n = 34) were included in the study. A control sample was identified by review of the exercise stress laboratory database (n = 35). Then HRR at baseline and on follow-up were compared.
Results: After completion of phase 2 cardiac rehabilitation, the HRR improved from 18 +/- 7 bpm to 22 +/- 8 bpm (P <.001). Among controls, the HRR on serial testing were 21 +/- 10 bpm and 21 +/- 9 bpm (P =.649). The mean difference in HRR on follow-up testing was different between those enrolled in a cardiac rehabilitation program and those who were not (P =.002).
Conclusion: Exercise training in a cardiac rehabilitation program results in HRR improvement. As a simple parameter for assessing autonomic tone, HRR may be used in a cardiac rehabilitation facility to identify patients with higher risk profiles, and can be useful for evaluating patient outcomes.