Effect of coronary artery bypass on QT dispersion

Introduction: QT dispersion (QT Max – QT min) reflects inhomogeneous ventricular depolarization that may provide a substrate for serious arrythmias and is associated with adverse clinical outcomes in patients with coronary artery disease. Some studies have shown reduction in QT dispersion after successful angioplasty due to coronary reperfusion, but effect of coronary artery bypass grafting on QTd is less known. This study evaluated the effects of coronary artery bypass grafting (CABG) on QT dispersion in first days after surgery. Methods: In this descriptive cross-sectional study, QTd of 50 patients who underwent coronary artery bypass grafting were calculated pre-and post-surgery This measurement was performed after surgery on three occasions (first day, third day and predischarge) in patients without serious or malignant arrythmias. Results: QTd & QTcd (mean SD) decreased in third postoperative day compared to preoperation values. QTd and QTcd decreased from 62.9 (26.9), and 64.8 (28.08) to 43.1 (22.8) and 59.4 (29.9) respectively (P<0.005 and P<0.03) in the third day after surgery comparing to presurgery. The decrements was more significant between predischarge and preoperation: QTd decreased from 62.2(26.9) to 41.6(24.16) and QTcd decreased from 71.7(32.47) to 51.5(27.69) (P<0.001). Conclusion: CABG, the most comprehensive method of revascularization in patients with coronary artery disease, is an important factor in reducing QT dispersion and eventually reducing malignat ventricular arrhythmia after surgery