Effects of ischemia and reperfusion on QT dispersion during coronary angioplasty

The effects of ischemia and reperfusion on QT interval dispersion (QTD: QTmax-QTmin in the 12-lead ECG) were analyzed in 15 patients (12 males, 57 +/- 13 years) undergoing coronary angioplasty (PTCA). All patients had single-vessel coronary artery disease (only one > or = 85% stenosis in a major coronary artery) and normal left ventricular function. All were in sinus rhythm with normal atrioventricular and intraventricular conduction on the surface ECG. No patient was on therapy that could affect the QT interval. The ECG was recorded (all 12 leads simultaneously) at 50 mm/s speed before the first balloon inflation, at the end of the first inflation during PTCA, and at 30" and 60" during reperfusion following the first inflation. In order to avoid ischemic preconditioning, only recordings of the first inflation were used. In each tracing QTmax and QTmin were evaluated. All values were rate corrected using a simple linear equation (QT linear corrected = QT + 0.154 [1-RR]). QTD increased significantly during both ischemia and reperfusion. QTmax was not changed by ischemia and was increased by reperfusion. QTmin was reduced by ischemia and increased by reperfusion. These results indicate that both ischemia and reperfusion alter ventricular repolarization, inducing a less homogeneous ventricular recovery pattern.