The diagnostic value of QT dispersion for acute coronary syndrome in patients with nondiagnostic initial electrocardiograms

Abstract

Introduction: Chest pain is a frequent cause for admission to the emergency department (ED). It can be a sign of various conditions, from a minor disorder to a life-threatening disease such as acute myocardial infarction (AMI). Despite the availability of modern-day tools for the diagnosis of AMI, about 5% of patients with AMI are missed in the ED, with subsequent associated morbidity and mortality. QT dispersion as a marker for arrhythmic potential being a marker of in-homogeneity of ventricular repolarization. The QT dispersion is increased in myocardial ischemia. Aims: This study we hypothesized that QTD could accurately identify patients with the acute coronary syndrome (ACS) who presented with chest pain and nondiagnostic initial electrocardiograms (ECGs). Subjects and Methods: The study population included (50) patients (37 males, 13 females) and (10) chronic stable ischemic patients as a control group, they were all in sinus rhythm on admission. All the studied patients were subjected to: History taking; complete physical examination was performed to rule out any other medical problems, standard 12-lead ECG, cardiac markers, echocardiographic examination. QT interval was calculated. The difference between the maximum and minimum QT intervals, occurring in any of the 12 leads, was measured as QTD. A corrected QT interval (QTc) of >440 ms is defined as abnormal, and the difference between QTc max and QTc min was calculated as QTcD. QT dispersion ≤40 ms was considered normal. Results: In the present study, we found that 26 patients (52%) have prolonged QTD (mean 78.800 ms, standard deviation [SD] ±49.555) and 44 patients (88%) have prolonged cQTD (mean 83.322 ms, SD ± 48.491) For patients who were admitted to the ED with chest pain and nondiagnostic initial ECG but later diagnosed as having ACS. Furthermore, we found that only 6 (12%) of patients have a significant prolongation QTD than normal in initial nondiagnostic ECG with elevated cardiac biomarkers (creatine kinase myocardial band at 0 h 48, mean creatine kinase myocardial band (CK MP) at 12 h was 145.833 ± SD 52.660, creatine phosphokinase (CPK) at 0 h: 635.33, mean CPK at 12 h 2448.66 ± SD 538.744). It has been suggested that the initial QTD level has a low predictive power for new cardiac events but that QTD can be more helpful for low-risk patients. Conclusion: Hence, in this study, we found that QTD and QTcD values are higher for ACS patients than for patients without ACS with nondiagnostic initial ECG.