• Isik Turker, Takeru Makiyama, Matteo Vatta, Hideki Itoh, Takeshi Ueyama, Akihiko Shimizu, Tomohiko Ai, and Minoru Horie.
• Krannert Institute of Cardiology, Indiana University, Indianapolis, IN, United States of America.
• Plos One. 2016 Jan 1; 11 (8): e0161872.

BackgroundClass IC antiarrhythmic agents may induce acquired forms of Brugada Syndrome. We have identified a novel mutation in SCN5A, the gene that encodes the α-subunit of the human cardiac sodium channel (hNav1.5), in a patient who exhibited Brugada- type ECG changes during pharmacotherapy of atrial arrhythmias.ObjectiveTo assess whether the novel mutation p.V1328M can cause drug induced Brugada Syndrome.MethodsAdministration of pilsicainide, a class IC antiarrhythmic agent, caused Brugada- type ST elevation in a 66-year-old Japanese male who presented with paroxysmal atrial fibrillation (PAF), type I atrial flutter and inducible ventricular fibrillation (VF) during electrophysiological study. Genetic screening using direct sequencing identified a novel SCN5A variant, p.V1328M. Electrophysiological parameters of WT and p.V1328M and their effects on drug pharmacokinetics were studied using the patch-clamp method.ResultsWhole-cell sodium current densities were similar for WT and p.V1328M channels. While p.V1328M mutation did not affect the voltage-dependence of the activation kinetics, it caused a positive shift of voltage-dependent steady-state inactivation by 7 mV. The tonic block in the presence of pilsicainide was similar in WT and p.V1328M, when sodium currents were induced by a low frequency pulse protocol (q15s). On the contrary, p.V1328M mutation enhanced pilsicainide induced use-dependent block at 2 Hz. (Ki: WT, 35.8 μM; V1328M, 19.3 μM).ConclusionOur study suggests that a subclinical SCN5A mutation, p.V1328M, might predispose individuals harboring it to drug-induced Brugada Syndrome.

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