SCN5A mutation and a short coupled variant of Torsades de Pointes originating from the right ventricle: A case report

A 40-year-old male visited our institute complaining of transient loss of consciousness. He had been implanted with an implantable cardioverter defibrillator (ICD) due to idiopathic ventricular fibrillation for secondary prevention. His past genetic screening detected a single nucleotide SCN5A mutation (pR18Q), while neither QT prolongation nor ST segment elevation in the right precordial leads was observed. An interrogation of the ICD revealed that a shock therapy successfully terminated ventricular fibrillation at the time syncope occurred. His electrocardiogram revealed ventricular premature contractions (VPCs) with a short coupling interval of 250 ms. Since the spontaneous occurrence of non-sustained polymorphic ventricular tachycardia following the same VPCs was observed after admission, he was diagnosed with a short-coupled variant of Torsades de Pointes (ScTdP). Contact mapping on the basal inferior right ventricular free wall, exhibiting the earliest activation, revealed pre-potentials preceding the QRS by 30 ms during the VPCs. Radiofrequency ablation was performed to reduce the triggering VPCs. To the best of our knowledge, this is the first report describing a case of ScTdP harboring an SCN5A mutation. The present N-terminally mutated SCN5A was originally reported in relation to Brugada syndrome, whereas the detailed mechanism remains to be elucidated.〈Learning objective: The fundamental genetic disorders of short-coupled variant of Torsades de Pointes (ScTdP) are not clear. The present case harboring a mutation of SCN5A exhibited no long-QT or Brugada syndrome, which may implicate an unknown mechanism of the development of ScTdP.〉