effect of exercise training on heart rate variability in patients with heart failure after percutaneous coronary intervention

Background: this study aims to evaluate the effect of exercise training on heart rate variability (hrv) and to determine the correlation between parameters of hrv and the ejection fraction in patients with heart failure after percutaneous coronary intervention. material and methods: fifty patients with left ventricular ejection fraction ≤ 40% undergone percutaneous coronary intervention were randomly allocated in either an exercise training (et) group or a control group. the et group performed exercise training for 45 minutes, three times a week for seven weeks. patients in both groups received a leaflet for daily exercising at home. hrv parameters comprising, the standard deviation of normal rr intervals (sdnn), the square root of the mean of the squares of successive rr intervals differences (rmssd) ,the percentage of successive rr intervals differing from more than 50 ms (pnn50), using 24hour holter electrocardiographic monitoring was measured.results: after the intervention, the sdnn improved in the et group (p=0.002), while changes in all remaining hrv indices were insignificant (p≥0.05). the control group showed no significant changes in any hrv parameters (p≥0.05). changes in sdnn in the et group were significantly different from the control group (p=0.003). at baseline, our results revealed a significant weak correlation between ejection fraction and sdnn (r =0.279, p=0.047). however, ejection fraction did not correlate significantly with rmssd and pnn50. conclusion: exercise training is safe and feasible in post percutaneous coronary intervention patients, even in those with reduced ejection fraction. in a sevenweek period, exercise training was effective in improving hrv in heart failure patients after percutaneous coronary intervention.