Significance of qt dispersion and U waves on perioperative electrocardiograms in patients undergoing coronary artery bypass grafting with intra-aortic balloon pumping

This study was designed to reveal the significance of QT dispersion (QTD) and U waves on perioperative electrocardiograms (ECGs) in patients who underwent coronary artery bypass grafting (CABG) supported with intra-aortic balloon pumping (IABP). The perioperative ECGs of 30 patients were examined retrospectively. Increased QTD was found before CABG in 38.4% of 13 patients with preoperative IABP and in 76.4 % of 17 patients with intraoperative IABP. This finding may suggest a suppressing effect of IABP on ventricular arrhythmogenesis. The ECGs immediately after CABG had significantly fewer U waves and a lower QTD than those before the operation. This may suggest protective effects on the myocardium of both CABG and IABP. Ten patients without U waves and QTD on the ECGs immediately after discontinuation of IABP all had improved or unchanged ECGs at discharge in comparison with those before the operation. In 75% of the patients whose ECGs at discharge were more aggravated than the preoperative ECGs, the leads showing U waves after discontinuation of IABP were identical with the leads having the aggravated findings at discharge. In other 25%, QTD was present on the ECGs immediately after discontinuation of IABP. In conclusion, U waves and QTD on perioperative ECGs may be considered as important indicators for evaluating myocardial ischemia in patients undergoing CABG supported with IABP.