Brugada Syndrome: Characterization of QT Interval Components and Correction

Brugada syndrome (BrS) is an inherited cardiac disorder at high risk of sudden death. There are two ECG patterns for BrS: Type 1 (coved-type), representing the only diagnostic pattern for BrS (BrS1), while type 2 (saddle-back type) is only suggestive of BrS (BrS2). The QT interval on surface ECG, known to be heart-rate (HR) dependent, characterizes ventricular activity and is associated with the risk of ventricular arrhythmias. Aim of this study is to investigate the role of QT-interval and QT-interval-segment correction in subjects with BrS1 and BrS2, compared to controls (CTR). Open-access “Brugada ECG Database” by Zenodo was considered, containing HR, QT interval and its segments (QJ, JTp, and TpTe) of 60 subjects with BrS1, 27 subjects with BrS2 and 51 CTR. Time intervals and segments were corrected according to nine correction formulae. Feature distributions of BrS1, BrS2 and CTR were compared by unpaired Wilcoxon rank sum test. All BrS1 and BrS2 features were statistically different from CTR. QT interval and corrected QT interval were significantly longer in BrS1 and BrS2 than in CTR, mainly due to longer QJ and TpTe, while JTp was significantly shorter in BrS1 and BrS2 than in CTR. No significant differences were observed in QJ and JTp between BrS1 and BrS2, whereas five correction formulae revealed that BrS1 had significantly longer TpTe interval than BrS2, suggesting physiological differences between BrS1 and BrS2 in late repolarization phase. In conclusion, major differences exist between BrS patients and CRT in QT-interval duration, mainly due to longer QJ and shorter JTp duration in BrS patients, while differences may exist between BrS1 and BrS2 patients in the late repolarization phase, highlighting the need of proper QT-HR correction to better characterize BrS patients.