The Frontal QRS-T Angle Remains Unchanged in Patients Without Structural Heart Disease Receiving Flecainide Therapy

Introduction: Prolongation of the QT interval and QRS duration, which are markers of ventricular repolarization and depolarization, has been reported in patients receiving flecainide therapy. However, the effects of flecainide on the QRS–T angle—a recognized indicator of transmural dispersion of repolarization—remain unclear. The aim of our study was to investigate the impact of flecainide therapy on the QRS–T angle. Method: In this study, 200 patients who were prescribed flecainide therapy due to atrial or ventricular arrhythmias were included. Prior to the initiation of flecainide treatment, all patients underwent a 12-lead electrocardiogram (ECG) in which heart rate (HR), PR and QRS durations, QT, QTc, JT, Tp–Te intervals and the frontal plane QRS–T angle were measured. At the 1-month follow-up, patients underwent repeat ECG recording and were evaluated for both cardiac and non-cardiac side effects of flecainide. The same ECG parameters were measured again using the follow-up recordings. Changes in ECG parameters between the baseline and 1-month post-treatment were analyzed. Results: Following flecainide administration, the drug was discontinued in 18 patients (9%) due to adverse effects (11 cases of cardiac and seven cases of non-cardiac). HR significantly decreased (78 ± 22 bpm to 74 ± 15 bpm and p < 0.05). PR interval and QRS duration significantly increased (148 ± 23 ms to 156 ± 9 ms and 89 ± 17 ms to 99 ± 19 ms, respectively p < 0.05 for each). Additionally, JT interval (326 ± 27 ms vs. 334 ± 6 ms), QT interval (416 ± 24 ms vs. 434 ± 24 ms), QTc interval (431 ± 24 vs. 447 ± 25 ms) and Tp–Te interval (84 ± 17 vs. 87 ± 18 ms) all showed statistically significant increases after flecainide treatment (p < 0.05 for-each). However, no significant change was observed in the frontal QRS–T angle. Discussion: In patients receiving flecainide therapy for atrial and ventricular arrhythmias, prolongation was observed in atrioventricular conduction, ventricular depolarization and repolarization parameters as measured by ECG. However, no significant change was detected in the frontal QRS–T angle.