A Review of the Mechanisms of Ventricular Arrhythmia in Brugada Syndrome

Brugada syndrome (BrS) is characterised by the triad of coved ST elevation, lethal ventricular arrhythmia in an apparently structurally normal heart. The precise mechanisms responsible for the coved ST elevation and ventricular arrhythmias in this disease have been debated since its initial description in 1992. Indeed the recent recognition of early repolarisation J wave disorders linked to primary VF broadens the mechanistic importance of BrS in sudden cardiac death. It may lie on a spectrum of early repolarisation pathology which is becoming increasingly recognised as a marker of premature cardiovascular death. Mechanistically, abnormalities of both depolarisation and repolarisation in the right ventricular outflow tract, and heterogeneities of conduction between the endocardium and epicardium have been implicated in the electrographic manifestations of BrS and arrhythmogenesis. The initial belief of BrS as a single autosomal dominant ion channel disorder has been challenged. It has become apparent that sodium channel mutations only account for a maximum of 30% of cases and structural myocardial abnormalities have now been described in what was previously thought to be a purely functional condition. It is highly probable that BrS is an umbrella diagnosis for a number of conduction and repolarisation abnormalities which manifest as this syndrome and the coved ST elevation represents the final common pathway of both ion channel and structural derangements. This review will discuss the issues surrounding the mechanisms of lethal arrhythmia in BrS and summarise both basic science and clinical research findings.