Abstract
Brugada syndrome (BrS) is a distinct form of idiopathic ventricular fibrillation (VF). BrS is characterized by a unique electrocardiographic pattern consisting of a right bundle branch block morphology and ST-segment elevation in the right precordial leads. There are 2 leading hypotheses for the mechanisms underlying BrS phenotype and arrhythmias: (1) The abnormal repolarization hypothesis (based on the canine wedge preparation), i.e., spatially heterogeneous loss of the action potential plateau in the right ventricular outflow tract (RVOT) can lead to reentry (phase 2 reentry). (2) The abnormal conduction hypothesis (based on whole-heart studies in BrS patients). In this review, the author describes the possible mechanisms based on the results of studies performed by the author and colleagues. The abnormal conduction hypothesis is supported by positive ventricular late potentials based upon signal averages ECG, higher incidence of inducible VF by programmed ventricular stimulation, the presence of fragmented and delayed potentials in the RVOT, and the higher prevalence of abnormal findings of the right ventricular biopsy specimen. On the other hand, the abnormal repolarization hypothesis is supported by the presence of STT alternans in the ECG and monophasic action potential duration alternans in the RVOT. High-resolution 187-channel ECG revealed that ECG phenotype was related to the spatial and transmural dispersion of repolarization, but lethal arrhythmia was related to the presence of ventricular late potential. Therefore, we hypothesize that the ECG phenotype of BrS may be related to both abnormal repolarization and conduction, and that the development of VF may be related mainly to abnormal conduction.
