Course and prognostic implications of QT interval and QT interval variability after primary coronary angioplasty in acute myocardial infarction

OBJECTIVES The aim of this study was to determine the influence of early reperfusion on the course of QT interval and QT interval variability in patients undergoing primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) and its prognostic implications on major arrhythmic events during one-year follow-up. BACKGROUND Although early coronary artery recanalization by primary angioplasty is an established therapy in AMI, a substantial number of patients is still threatened by malignant arrhythmias even after early successful reperfusion, which may be caused by an inhomogeneity of ventricular repolarization despite reperfusion. METHODS Temporal fluctuations of ventricular repolarization were studied prospectively in 97 consecutive patients with a first AMI by measurements of QT interval and QT interval variability during and after successful PTCA (Thrombolysis in Myocardial Infarction flow grades 2 and 3). Continuous beat-to-beat QT interval measurement was performed from 24-h Holter monitoring, which was initiated at admission before PTCA. RESULTS Reperfusion caused a significant continuous increase of mean RR interval (738 ± 98 to 808.5 ± 121 ms; p < 0.001) and a significant decrease of parameters of QT interval (QTc: 440 ± 32 to 416.5 ± 37ms; p < 0.001) and QT interval variability (QTcSD: 27.5 ± 3 to 24.9 ± 6 ms; p < 0.001) in the majority of patients. However, in patients with major arrhythmic events at the one-year follow-up (sudden cardiac death, ventricular fibrillation or sustained ventricular tachycardia, N = 15), parameters of QT interval remained unaltered after successful reperfusion (QTc: 447.3 ± 41 to 432.9 ± 45 ms, P = NS; QTcSD: 35.1 ± 13.4 to 29.0 ± 9.1 ms, P = NS). CONCLUSIONS Reduction of QT interval and QT interval variability after timely reperfusion of the infarct-related artery may be a previously unreported beneficial mechanism of primary PTCA in AMI, indicating successful reperfusion.