A new criteria differentiating type 2 and 3 Brugada patterns from ordinary incomplete right bundle branch block

The type 1 (coved) ECG pattern is diagnostic for Brugada syndrome; types 2 and 3 require antiarrhythmic drug challenge to confirm its presence. We evaluated a 12-lead ECG-based criterion to differentiate between ordinary incomplete right bundle branch block (iRBBB) and true type 2 and 3 patterns that evolve toward type 1 during drug challenge. The subjects were 22 patients (21 men, 1 woman; mean age, 46.8 ± 13.2 years) referred for drug challenge (1 mg/kg pilsicainide, iv). In magnified ECG lead V1 and/or V2 with an iRBBB pattern, the baseline angle defined as the cross section of the upslope of the r' wave with the downslope of the r' wave was measured and compared between patients responding negatively versus positively to drug challenge, and was found to be significantly smaller in patients responding negatively (20.9 ± 12.9°, n = 6, versus 38.7 ± 16.5°, n = 13; P = 0.009). This ECG-based method successfully discriminates between the ordinary iRBBB pattern and drug-induced evolution toward a type 1 Brugada ECG.