Gamma-glutamyl transpherase (GGT) plays an important role in atherogenesis through its activity in oxidative processes, which has been demonstrated in clinical studies. The connection between serum GGT activity and noninvasive arrhythmia indicators in patients with coronary artery disease (CAD) is investigated in the present study. We examined patients (n = 254, 174 males, mean age 62 ± 8) diagnosed with coronary artery disease on the basis of clinical and angiographic findings. All patient data were assessed, including serum GGT activity, biochemical measurements, and demographic and electrocardiographic features. A positive correlation was found between GGT levels and P-wave dispersion (r = 0.299, p < 0.0001); however, there was a negative correlation between GGT and ejection fraction (r = 0.216, p < 0.001). On the other hand, no correlation was found between GGT and the following: Sokolow-Lyon voltage, Cornell voltage, Cornell product, corrected QT, and QT dispersion (p values are 0.728, 0.892, 0.551, 0.069, and 0.146, respectively). When the patients were grouped according to gender, a significant association of GGT with P-wave dispersion and ejection fraction was observed in both of the groups. Nonetheless, a significant correlation between GGT and QTc was only found in the female group. In this study, we found that increased GGT activity was correlated with P-wave dispersion. These results indicate that there might be an increased risk of arrhythmias especially the atrial fibrillation in this patient population. [ABSTRACT FROM AUTHOR]