title: Differential effects of cardiac sodium channel mutations on initiation of ventricular arrhythmias in patients with Brugada syndrome.
abstract: BACKGROUND
  Premature ventricular contractions (PVCs) do not occur frequently but can induce ventricular fibrillation (VF) in patients with Brugada syndrome. The effect of SCN5A mutation on the onset of ventricular arrhythmias is unknown.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate PVC morphology and onset of VF in patients with Brugada syndrome.
  
  
  METHODS
  Morphology of PVCs was evaluated by 12-lead ECG in 32 patients with Brugada syndrome. Patients had spontaneous ventricular arrhythmia (n = 17) or sodium channel blocker-induced ventricular arrhythmia (n = 19). Patients were classified into two groups according to the existence of SCN5A mutation (22 mutation negative, 10 mutation positive).
  
  
  RESULTS
  Patients without mutation often had PVCs of left bundle branch block (LBBB) morphology (82%), especially with inferior axis (77%). Patients with mutation had PVCs of both right bundle branch block (36%) and LBBB (64%) morphologies. Only two patients with mutation had PVCs of LBBB, inferior-axis morphology.
  
  
  CONCLUSIONS
  Patients without SCN5A mutation often had PVCs of LBBB, inferior-axis morphology, suggesting a right ventricular outflow tract origin. Patients with SCN5A mutations had PVCs that originated from both the right and left ventricles.
authors.affiliation: Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine and Dentistry, Okayama City, Okayama, Japan. hmorita@cc.okayama-u.ac.jp
authors.forename: Hiroshi
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authors.lastname: Morita
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authors.lastname: Morita
authors.forename: Takefumi
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authors.forename: Kengo F
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authors.lastname: Kusano
authors.forename: Tohru
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