Usefulness of Resting 12-lead Electrocardiogram in the Diagnosis of Coronary Artery Disease

Kim, Nam Ho; Park, Woo Suck; Kim, Joon Woo; Kim, Sung Hee; Kim, Ju Han; Bae, Youl; Ahn, Young Keun; Park, Joo Hyung; Jeong, Myung Ho; Cho, Jeong Gwan; Park, Jong Chun; Kang, Jung Chaee

Abstract

Objectives
Twelve-lead electrocardiography (ECG) is widely used in clinical practice as a routine cardiology test. The value of ECG has been confirmed in the diagnosis of cardiac arrhythmias and myocardial infarction, but questioned in the diagnosis of coronary artery disease (CAD) without myocardial infarction. Recently, QT dispersion has been reported to increase in ischemic heart disease, particularly high risk patients for ventricular tachyarrhythmias. The purpose of this study was to determine the value of ECG in the diagnosis of CAD using the conventional parameters of myocardial ischemia and various indices of QT dispersion. Methods : One hundred-two (Group I) with significant stenosis in one or more major coronary artery branches and age and sex-matched 102 normal control subjects (Group II) who visited our hospital for routine health examination were included in the present study. Any patients with Q-wave myocardial infarction regardless of age were excluded. Resting 12-lead ECG and coronary angiogram were analysed separatively and their findings were compaed. The conventional criteria were applied in the interpretation of resting ECGs. Results : There was no significant difference in age and sex distribution between 2 groups. ECG was completely normal in 25.5% of Group I and 38.2% of Group II with significant difference between 2 groups (p>0.05). The incidence of normal ECG was 23.8% in patients with one-vessel disease, 34.3% in patients with two-vessel disease, and 25.5% in patients with three-vessel disease, showing no significant difference according to the extent of coronary artery disease. There were significant differences between Group I and II in the incidences of abnormal ST-segment (1.0% vs. 18.6%, p>0.05), abnormal T wave (12.7% vs. 45.1%, p>0.05), and QTc prolongation (6.9% vs. 19.6%, p>0.05). QT dispersion (QTmax-min) was 65+/-26 ms in Group I and 53+/-20 ms in Group II with significant difference between 2 groups (p>0.05). In diagnosing coronary artery disease, the sensitivities of abnormal ST-segment , abnormal T wave , and QTc prolongation were 18.6%, 47.1%, and 19.6%, respectively. The sensitivity of QT dispersion with a cut-off value of 55 ms was 61.8%, which was slightly higher than those of the conventional parameters. Abnormal ST-segment, intraventricular conduction disturbance, and QTc prolongation were the 3 parameters with highest specificity (99.0%, 98.0%, 93.1%, respectively). However, the diagnostic accuracies of these parameters were 58.8%, 51.0%, and 56.4%, respectively. Conclusion : We conclude that abnormal ST-segment, abnormal T wave change, QTc prolongation, and increased QT dispersion of resting 12-lead ECG may be used to diagnose coronary artery disease, but their value are limited due to low sensitivities and diagnostic accuracies. Therefore, other diagnostic tests with higher sensitivity and accuracy should be performed if CAD is clinically suspected.