QT dispersion, a simple tool to predict ventricular tachyarrhythmias and/or sudden cardiac death after myocardial infarction

Recent studies showed contradictive results of the relation between QT dispersion and the occurrence of ventricular tachyarrhythmias and/or sudden cardiac death. In addition, beta adrenoreceptors blocking agents, which are known to decrease the incidence of lethal arrhythmias after myocardial infarction, administered to the majority of patients in those studies population. Since -blocker as secondary prevention drug was underutilized at National Cardiovascular Center Harapan Kita, this study was performed to find out the relation between QT dispersion and ventricular tachyarrhythmias and/or sudden cardiac death after previous myocardial infarction. The QT interval duration, QT dispersion and clinical variables of 36 postinfarction patients with history of sustained ventricular tachyarrhythmias and/or sudden cardiac death (event group) were compared with 75 postinfarction patients without such events (control group). QT dispersion differed significantly between study groups and was increased in the event group (115  41 msec vs 81  25 msec, p < 0.001). Corrected maximal QT interval duration was also prolonged in the event group (53456 vs 50135 msec, p < 0.001). Regression analysis showed that increasing QT dispersion was related to the occurrence of ventricular tachyarrhythmias and/or sudden cardiac death with OR of 3.2, 4, and 5.8 for cut-off point of 80, 90, and 100 msec respectively. The QT dispersion could predict the occurrence of ventricle tachyarrhythmias and/or sudden cardiac death in patient with AMI. This study confirmed that the QTd remain useful in free of beta blocking agents state. (Med J Indones 2005; 14: 230-6) Keyword : QT dispersion, Acute myocardial infarction, Sudden death. Sudden cardiac death (SCD) is continuing as major problem in the management of heart disease. Approximately 400,000 Americans die suddenly each year, and it is the most common form of death in the United States. 1 Among myocardial infarction (MI) patients discharge from hospital, 10 % were die in the first year. One third of the deaths are sudden death, presumably due to ventricular arrhythmias. 2 Adgey et al 3 , reported that when electrocardiogram was obtained within 4 minutes from the onset of symptoms of cardiac arrest, the majority of patients (91%) exhibited ventricular fibrillation, which was consistent to the finding of Klein et al. 4 Many efforts are perform to Department of Cardiology and Vascular Medicine, Faculty of Medicine University of Indonesia and National Cardiovascular Center Harapan Kita, Jakarta, Indonesia Vol 14, No 4, October – December 2005 Simple predictor of arrhythmic death 231 identify patients at risk of sudden death after acute myocardial infarction (AMI). Emerging data demonstrated that QT dispersion (QTd) is a new hope as a simple method to predict SCD after AMI. Unfortunatelly, such studies have difference and even contradictive results. 5,6,7,8,9,10 Another issue is beta blocking agents. The majority of current studies did not exclude beta blocking agents users from their study population. 5,9 Meanwhile, the MIAMI trial showed that beta blocking agents has been proven to decrease the incidence of ventricle fibrillation in AMI. 11 Meta-analysis by Yusuf et al 12 showed that beta blocking agents decrease the incidence of lethal arrhythmias by 15%. Furthermore Singh et al 13 showed beta adrenoreceptor agent may blunt circadian variation of QT interval. Therefore, it is ethically notworthy to design the study of post myocardial infarction patients by avoiding beta blocking agents administration. Meanwhile, the utility of beta blocking agents in acute myocardial infarction at National Cardiovascular Center Harapan Kita (NCCHK) was small. Yuniadi et al 14 found only 13% acute MI patients were given beta blocking agents when discharged from NCC-HK. The aim of this study is to elucidate the relation between QTd with ventricular tachyarrhythmia and/or sudden cardiac death after myocardial infarction without influence of beta blocking agents.