Electrophysiological Mechanisms of Brugada Syndrome: Insights from Pre-clinical and Clinical Studies

This is the final version of the article. It first appeared from Frontiers via https://doi.org/10.3389/fphys.2016.00467Brugada syndrome (BrS), is a primary electrical disorder predisposing affected individuals to sudden cardiac death via the development of ventricular tachycardia and fibrillation (VT/VF). Originally, BrS was linked to mutations in the SCN5A, which encodes for the cardiac Na$^{+}$ channel. To date, variants in 19 genes have been implicated in this condition, with 11, 5, 3, and 1 genes affecting the Na$^{+}$, K$^{+}$, Ca$^{2+}$, and funny currents, respectively. Diagnosis of BrS is based on ECG criteria of coved- or saddle-shaped ST segment elevation and/or T-wave inversion with or without drug challenge. Three hypotheses based on abnormal depolarization, abnormal repolarization, and current-load-mismatch have been put forward to explain the electrophysiological mechanisms responsible for BrS. Evidence from computational modeling, pre-clinical, and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening VT/VF. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction and based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers.GT received a BBSRC Doctoral CASE Studentship at the University of Cambridge and thanks the Croucher Foundation of Hong Kong for the support of his Clinical Assistant Professorship. YC is supported by the ESRC for her Ph.D. studies at the University of Cambridge. BY received funding from the Research Grant Council of Hong Kong for his research