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Impaired heart rate recovery (HRR) after exercise, which is a marker of reduced parasympathetic activity, predicts mortality and cardiovascular disease events of patients with heart disease. Although exercise-based cardiac rehabilitation has been well known to decrease of cardiovascular disease or all-cause mortality, these mechanisms are not complete understand. There is few data to the impact of HRR after exercise in cardiac rehabilitation program. Therefore, we examined the effects of exercise training in cardiac rehabilitation program to changes of HRR. 32 male patients (56.3 ±11.1 yrs) with PCI who participated phase II cardiac rehabilitation program were randomly assigned into the exercise group (n=16) or the control group (n=16) who did not attend cardiac rehabilitation. Exercise group was instructed to continue prescribed aerobic type exercise at 50 to 80% of maximal heart rate reserve for 45 to 60 minutes a session, 3 days per week. All patients underwent a symptom-limited exercise test with modified Bruce protocol at baseline and after 8 weeks. The value for the HRR was calculated as the difference between HR at peak exercise and HR at 1 minute (HRR1) of the recovery period during exercise test. At baseline, there were no significant differences in HRR 1 and other parameter in between group. After 8 weeks, the HRR1 was significantly increased in exercise group (21.2±9.9 to 25.8±12.7, p=0.041), but no significantly increased in control group (22.3±7.1 to 22.6±8.2, p=0.878). There were also significant differences in between group (p<0.001). Increased of HRR after exercise training might be due to improve in parasympathetic nervous activity, which could contribute to decrease risk of sudden cardiac death in patients with enrolled exercise-based cardiac rehabilitation.