Relation of QT-interval variability to ventricular arrhythmias during percutaneous transluminal coronary angioplasty

The present study investigated the role of the dispersion of QT interval in percutaneous transluminal coronary angioplasty (PTCA)-induced ventricular tachyarrhythmias. Patients with effort angina without a previous myocardial infarction (n=22), who had single-vessel disease of the anterior descendin g coronary artery (LAD), underwent PTCA if the coronary lesion was 75% or m ore stenosed in segment 6 or 7 of the LAD. The standard 12-lead ECG was con tinuously recorded during the procedure. Averaged QTc and QTac intervals, w here QTac was the interval from the beginning of QRS complex to the nadir o f T wave corrected by Bazett's formula, did not change significantly during PTCA. Of the 22 patients, 7 showed ventricular arrhythmias during PTCA. Th e maximum difference (Delta QTc) and the standard deviation (QTcSD) of the corrected QT interval in the standard 12-lead ECG increased significantly d uring PTCA in the 7 patients with ventricular arrhythmias, whereas they dec rreased in the 15 patients without ventricular arrhythmias. Delta QTac and QTacSD were not affected by PTCA regardless of ventricular arrhythmias, whi ch shows that the increases in the variation of the ventricular repolarizat ion process playa role in PTCA-induced ventricular arrhythmias.