Brugada Syndrome: From Molecular Mechanisms and Genetics to Risk Stratification

Abstract

Brugada syndrome (BrS) is a rare hereditary arrhythmia disorder, with a distinctive ECG pattern, correlated with an increased risk of ventricular arrhythmias and sudden cardiac death (SCD) in young adults. BrS is a complex entity in terms of mechanisms, genetics, diagnosis, arrhythmia risk stratification, and management. The main electrophysiological mechanism of BrS requires further research, with prevailing theories centered on aberrant repolarization, depolarization, and current-load match. Computational modelling, pre-clinical, and clinical research show that BrS molecular anomalies result in excitation wavelength (k) modifications, which eventually increase the risk of arrhythmia. Although a mutation in the SCN5A (Sodium Voltage-Gated Channel Alpha Subunit 5) gene was first reported almost two decades ago, BrS is still currently regarded as a Mendelian condition inherited in an autosomal dominant manner with incomplete penetrance, despite the recent developments in the field of genetics and the latest hypothesis of additional inheritance pathways proposing a more complex mode of inheritance. In spite of the extensive use of the next-generation sequencing (NGS) technique with high coverage, genetics remains unexplained in a number of clinically confirmed cases. Except for the SCN5A which encodes the cardiac sodium channel NaV1.5, susceptibility genes remain mostly unidentified. The predominance of cardiac transcription factor loci suggests that transcriptional regulation is essential to the Brugada syndrome's pathogenesis. It appears that BrS is a multifactorial disease, which is influenced by several loci, each of which is affected by the environment. The primary challenge in individuals with a BrS type 1 ECG is to identify those who are at risk for sudden death, researchers propose the use of a multiparametric clinical and instrumental strategy for risk stratification. The aim of this review is to summarize the latest findings addressing the genetic architecture of BrS and to provide novel perspectives into its molecular underpinnings and novel models of risk stratification.

Keywords: Brugada syndrome; SCN5A; arrhythmias; genetics; genome-wide association; loci; molecular mechanism; mutations; sudden cardiac death; susceptibility.

Figure 1

Schematic representation of the three electrophysiological theories behind BrS; AP (action potential); APD (action potential duration); CV (conduction delay); I_to (transient outward potassium current); I_CaL (L-type Ca²⁺ current); TDR (transmural dispersion of repolarization).

Figure 2

Schematic representation of the proposed markers for risk stratification in Brugada syndrome; BrS (Brugada syndrome); SCN5A (sodium channel protein type V subunit α gene); RVOT (right ventricle outflow tract); PES (programmed electrical stimulation); AV (atrioventricular); iCEB (index of Cardiac Electrophysiological Balance); SAECG (signal-averaged ECG); RMS40 (root mean square voltage of the QRS complex terminal 40 ms); LAS40 (duration of low amplitude signals <40 µV of the QRS complex); ECG-I (electrocardiographic imaging).