Effect of Exercise-Based Cardiac Rehabilitation Following Coronary Artery Bypass Surgery on Ventricular Repolarization Indices

Abstract

Indices of ventricular repolarization heterogeneity are associated with future arrhythmias and sudden cardiac death. We investigated the effect of exercise-based cardiac rehabilitation (CR) on these indices in a sample of Iranian patients. Patients (N 122), who had undergone coronary artery bypass surgery (CABGS), were enrolled in this cohort study. Sixty patients attended 15 or more sessions of CR (CR group) and the remaining 62 patients attended 5 or fewer sessions of CR (control group). A standard 12-lead electrocardiogram was recorded for each patient. QT interval dispersion (QTd), RR interval variability (RRV), and heart rate-corrected QTd (QTc-d) were measured 3 times as follow: just before surgery, at the beginning of the first session of the CR program, and at the end of the 15th session for the CR group or the last session for the control group. Following completion of the exercise-training program, the CR group showed a significant decrease in QTd (Δ = -49.4%, P < .0001) and QTc-d (Δ = 52.8%, P .0001), but not in the control group (Δ = 13.4% and 17.9%, respectively, P > .05 for both). In both groups, no statistically significant change in RRV was observed. After adjustment for variables such as age, gender, digoxin use, β-blocker use, and prerehabilitation ejection fraction, CR remained the independent predictor of QTd and QTc-d. Results suggest that cardiac rehabilitation and exercise training programs significantly improve the indices of ventricular repolarization heterogeneity in patients with coronary artery disease who received CABGS.