BACKGROUND: The aim of this study was to predict significant coronary artery disease (CAD) in patients undergoing coronary angiography.METHODS: In this cross-sectional study, data of 384 patients who underwent angiography during 2015-2017 were reviewed. Electrocardiograms (ECGs) were evaluated in terms of having positive T wave in lead V1 (TV1) described as T wave with amplitude of more than 0.15 mV and angiography records were assessed for presence of significant CAD defined as presence of ≥ 70% internal diameter stenosis in at least one major epicardial coronary artery or more than 50% stenosis in left main artery (LMA).RESULTS: Out of 384 patients who participated in this study with mean age of 63.6 ± 10.2 years (40-89 years), 71.6% showed positive TV1 and significant CAD simultaneously and left anterior descending artery (LAD) and left circumflex artery (LCX) lesions were more frequently reported in coronary angiography. Based on chi-square test, the prevalence of significant CAD was obviously more in those with positive TV1 as compared to those without this finding [odds ratio (OR) = 2.74, 95% confidence interval (CI): 1.80-4.19, P < 0.001]. Mann-Whitney test showed significant difference in number of coronary arteries involved in CAD between presence of positive and negative T wave in lead V1 (P < 0.001). Great number of patients with significant CAD had remarkably higher T wave amplitude in lead V1 in comparison to lead V6 (OR = 6.22, 95% CI: 3.14-12.30, P < 0.001).CONCLUSION: Positive TV1 and TV1 > TV6 pattern can be considered as a predictor forsignificant CAD in patients with otherwise normal ECG.