title: Clinical and electrocardiographic predictors of positive response to the intravenous sodium channel blockers in patients suspected of the Brugada syndrome.
abstract: OBJECTIVE
  Sodium channel blockers are used to unmask the diagnostic ECG pattern of the Brugada syndrome (BrS) in case of a non-diagnostic baseline ECG. The aim of the study was to determine clinical and ECG predictors of a positive challenge test in patients suspected to the BrS.
  
  
  METHODS
  A total of 106 consecutive patients (91 men; mean age, 35 ± 12 years) suspected of the BrS underwent the intravenous sodium channel blocker challenge test with procainamide or flecainide.
  
  
  RESULTS
  Of the 106 patients, positive tests were detected in 20 (19%) patients. During test, a transient episode of a second-degree atrioventricular block and isolated ventricular ectopies were observed in 1 (0.9%) and 2 (1.9%) patients, respectively. A QRS prolongation ≥ 30% was observed in 4 (3.8%) patients. Baseline QRS duration in V1 ≥ 110 ms had a sensitivity of 70% and a specificity of 80% for a positive response. An ST-segment elevation ≥ 0.17 mV in V2 had a sensitivity of 60% and a specificity of 82% for a positive response. Of the multiple clinical and ECG variables entered into a binary logistic regression analysis, a history of syncope (P=0.001), previous cardiac arrest (P=0.001), baseline QRS duration in V1 ≥ 110 ms (P=0.001), and baseline ST-segment elevation in V2 ≥ 0.17 mV (P=0.012) emerged as the independent predictors of a positive response to the intravenous challenge with sodium channel blockers.
  
  
  CONCLUSIONS
  The results of the sodium channel blocker challenge test can be predicted by clinical presentation and baseline ECG features.
authors.affiliation: Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical and Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Shahab
authors.initials: S
authors.lastname: Shahrzad
authors.forename: Maryam
authors.initials: M
authors.lastname: Khoramshahi
authors.forename: Amir
authors.initials: A
authors.lastname: Aslani
authors.forename: Amir Farjam
authors.initials: AF
authors.lastname: Fazelifar
authors.forename: Majid
authors.initials: M
authors.lastname: Haghjoo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D053840:Brugada Syndrome / Q000175:diagnosis* / Q000503:physiopathology*; D004562:Electrocardiography / Q000187:drug effects* / Q000379:methods; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D026941:Sodium Channel Blockers / Q000008:administration & dosage*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D026941:Sodium Channel Blockers