Impact of Phase II cardiac rehabilitation on abnormal heart rate recovery

BACKGROUND: A delayed decrease in heart rate recovery (HRR) following a maximal exercise test is a predictor of mortality in healthy adults and in those referred for diagnostic testing evaluation. Cardiac rehabilitation (CR) has been proven to be beneficial in the treatment of numerous diseases. The purpose of this retrospective study was to explore the relationship between CR and improvement of HRR and to determine which factors can be predictive for the improvement of abnormal HRR after Phase II CR. METHODS: We reviewed the medical histories of patients referred for symptom-limited cardiopulmonary treadmill testing with abnormal HRR. Each patient underwent exercise testing before and after Phase II CR, and parameters including functional aerobic impairment, metabolic equivalent, anaerobic threshold (AT), and %AT were recorded and compared. RESULTS: Of the 25 patients recruited, 13 patients showed no abnormal HRR after Phase II CR. The functional capacity of these patients was improved after Phase II CR, to a statistically significant extent; the aerobic capacity (as expressed with AT and %AT) showed improvement, but without statistical significance. CONCLUSION: There are multiple factors of cardiopulmonary exercise tests that cannot be used to predict the effect of Phase II CR on the improvement of abnormal HRR. Forty-one percent of patients with abnormal HRR could improve after Phase II CR, but all of the patients could have improved exercise capacity regardless of whether or not HRR improved. We can conclude that HRR and exercise capacity change independently. However, it is important to closely follow-up during Phase III CR for patients with persistently abnormal HRR after Phase II CR has been completed.