Sodium-channel blocker challenge in the familial screening of Brugada syndrome: safety and predictors of positivity.

Sodium channel blocker challenge (SCBC) is frequently performed to unmask Brugada syndrome (BrS).We aim to identify, predictors of positivity and complications of SCBC, in the setting of familial screening.All consecutive patients from 2000 to 2014 who benefit from a SBC and belong to a family with at least 2 subjects affected by the syndrome were enrolled and followed prospectively. Data were reviewed by 2 physicians blinded to the clinical and genetic status.Among 672 SCBC performed in 137 families, 337(50%) were positive. Multivariate analysis identified ajmaline (OR 2.98 (1.65-4.91), a significant S wave in DII (OR=3.11 (2.12-4.58), DIII (OR= 2.75 (1.78-4.25) or V5 lead (OR= 3.71 (2.54-5.44), as predictors of a positive SCBC (P <0.0001). Eleven (1.6%) patients presented complications (10 ventricular arrhythmia, 1 atrial flutter) but no deaths occurred. A familial history of complications (OR = 41 [10; 203]; P<0.0001), young age (P =0.04) and decreased conduction ECG parameters at baseline (p=0.04) were predictors of complication. QRS enlargement during SCBC was not associated with complications. During a median follow-up of 106 [54-143] months, 11 life-threatening arrhythmia occurred.SCBC in the screening of familial Brs is safe. The risk of complication is considerably increased in case of familial history of complicated SCBC, in very young patients and in the presence of decreased ECG conduction parameters. However, QRS enlargement during the test is not directly related to complications and should not be used to prematurely stop the test unless leading to false negative results.