The coronary slow flow (CSF) phenomenon is defined as a microvascular disorder characterized by the slow filling of the opaque material applied during coronary angiography into the distal vasculature in patients with normal or near-normal epicardial coronary arteries [1]. CSF is detected in 1–7% of patients who undergo coronary angiography [2]. CSF has been reported to be closely related to endothelial dysfunction, impaired micro vascularization functions, and atherosclerosis [3,4]. Patients with CSF may present with exertional angina, unstable angina pectoris, myocardial infarction, life-threatening arrhythmias, and sudden cardiac death [5,6].

In patients with CSF, fatal cardiac arrhythmias may be caused by the impairment of the autonomic balance of the heart and disruption of myocardial blood flow by causing electrical abnormalities and changing ventricular repolarization [7]. Sarıkaya et al. examined the heart rate variability and heart rate turbulence parameters in patients with coronary slow flow and showed that the autonomic balance of the heart was impaired. They reported that this impairment may predispose to arrhythmia and lead to sudden cardiac death [8].

Previous evidence of the effect of coronary slow flow on electrocardiographic (ECG) markers has shown that ventricular repolarization parameters are significantly higher in patients with CSF than in subjects with normal coronary flow. Myocardial repolarization and depolarization were evaluated using various methods such as QT interval (QT), QT dispersion (QTd), transmural dispersion of repolarization, and QRS duration. On the electrocardiogram (ECG), the Tpeak-Tend interval between the peak and end of the T wave is considered the transmural dispersion index of ventricular repolarization [9]. Recently, new parameters (index of cardiac-electrophysiological balance, QRS-T angle) have been defined to predict malignant ventricular arrhythmias. The index of cardiac-electrophysiological balance (iCEB), which is equivalent to the heart wavelength λ, is a new and noninvasive marker [10]. It is obtained by dividing the QT interval by the QRS duration. The spatial QRS-T angle is a new marker of myocardial repolarization and is defined as the angle difference between the direction of ventricular depolarization (QRS wave) and the direction of ventricular repolarization (T wave) [11]. The QRS-T angle in the frontal plane, on the other hand, may be easily assessed using the automated report feature of ECG devices and correlates well with the spatial QRS-T angle in risk estimation [12]. Therefore, the frontal QRS-T angle has received greater attention than the spatial QRS-T angle, and an increased frontal QRS-T angle is linked with worse cardiac outcomes [13].

To the best of our knowledge, there is no study in which QT interval, Tp-e interval, index of cardiac-electrophysiological balance (iCEB), and frontal QRS-T angle were evaluated together in patients with CSF. In this study, we examined for the first time the relationship between all these myocardial repolarization parameters and CSF.