www.jcrpjournal.com QT Dispersion and CR Following CABGS / 239 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. ■ PURPOSE: Indices of ventricular repolarization heterogeneity are associat- ed 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. ■ METHODS: 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. ■ RESULTS: Following completion of the exercise-training program, the CR group showed a significant decrease in QTd (=-49.4%, P  .0001) and QTc-d (= 52.8%, P  .0001), but not in the control group (= 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, -blocker use, and prerehabilitation ejection fraction, CR remained the independent predictor of QTd and QTc-d. ■ CONCLUSION: 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. Effect of Exercise-Based Cardiac Rehabilitation Following Coronary Artery Bypass Surgery on Ventricular Repolarization Indices Ali Vasheghani-Farahani, MD; Leila Asef-Kabiri, MD; Farzad Masoudkabir, MD, MPH; Gholamreza Davoodi, MD; Mostafa Nejatian, MD; Soheil Saadat, MD, MPH, PhD; Tahereh Yazdani, MD; Baharak Mehdipoor, MD; Ahmad Yaminisharif, MD Author Affiliations: Department of Cardiology, Tehran Heart Center (Drs Vasheghani-Farahani, Davoodi, Nejatian, and Yaminisharif), Faculty of Medicine (Dr Asef-Kabiri), Students’ Scientific Research Center (Dr Masoudkabir), Research Department, Tehran Heart Center (Dr Nejatian), Sina Trauma Research Center (Dr Saadat), Obesity Research Center Sina University Hospital (Dr Yazdani), and Research & Develop- ment Center, Sina University Hospital (Dr Mehdipoor), Tehran University of Medical Sciences, Tehran, Iran. Correspondence: Ali Vasheghani-Farahani, MD, Tehran Heart Center, Karegar Shomali St, Jalal al-Ahmad Cross, Tehran, Iran, 1411713138 (avasheghani@sina.tums.ac.ir). DOI: 10.1097/HCR.0b013e318211e3c0 K E Y W O R D S cardiac rehabilitation coronary artery bypass surgery QT dispersion Phase II cardiac rehabilitation programs (CR) are asso- ciated with a significant improvement in functional work capacity, exercise tolerance, and long-term prog- nosis as well as increased psychosocial well-being. 1-6 Based upon such knowledge, CR is progressively used in patients undergoing coronary artery bypass graft surgery (CABGS). 7 QT dispersion (QTd), the difference between max- imum and minimum QT intervals on a 12-lead surface electrocardiogram (ECG), has been shown to be a