Prolonged QT interval at onset of acute myocardial infarction in predicting early phase ventricular tachycardia

Abstract

The prospectively assessed time course of changes in ventricular repolarization during acute myocardial infarction (AMI) is reported in 32 patients admitted 2.0 ± 1.8 (SD) hours after AMI onset. The initial corrected QT interval (QT c) upon hospitalization was longer (0.52 ± 0.07 seconds) in the 14 patients developing ventricular tachycardia (VT) within the first 48 hours as compared to QT c (0.47 ± 0.03 seconds) in the eight patients with frequent ventricular premature beats (VPBs) and to QT c (0.46 ± 0.03 seconds) in the 10 patients with infrequent VPBs ( p < 0.001; analysis of variance). By the fifth day after AMI onset, the QT c shortened significantly only in the VT group, suggesting a greater initial abnormality of repolarization in these patients. All 32 patients had coronary anglography, radionuclide ventriculography, and myocardial perfusion scintigraphy before hospital discharge. Significant discriminating factors related to early phase VT in AMI included initially longer QT and QT c intervals, faster heart rate, higher peak serum levels of creatine kinase, acute anterior infarction, anglographically documented proximal stenosis of the left anterior descending coronary artery, and scintigraphic evidence of hypoperfusion of the interventricular septum. Prior infarction, angina pectoris, hypertension, multivessel coronary artery disease, and depressed left ventricular ejection fraction did not provide discrimination among the three different ventricular arrhythmia AMI groups. We conclude that (1) the QT interval is frequently prolonged early in AMI, (2) the initial transiently prolonged ventricular repolarization facilitates and predicts complex ventricular tachyarrhythmias within the first 48 hours of AMI, (3) jeopardized blood supply to the interventricular septum frequently coexists, and (4) therapeutic enhancement of rapid recovery of the ventricular repolarization process merits investigation for prevention of VT in AMI.