LAUSR

A Brugada syndrome (BrS) diagnosis is made upon documenting its characteristic type-1 ECG abnormality, being either spontaneously present or provoked by drug challenge, in the absence of co-morbidities resulting in similar ECG characteristics. In patients without type-1 ECG but in whom a suspicion of BrS exists, several ECG characteristics have been proposed that could aid in distinguishing BrS from non-BrS, particularly in individuals with incomplete right bundle branch block. To validate the diagnostic value of ECG characteristics that were previously proposed. For this retrospective study, ECGs were evaluated from consecutive patients suspected of BrS who underwent ajmaline testing (n=1392). Baseline ECG and peak-effect ECG were analyzed with the MEANS software. Parameters considered were P, PR, QRS, S, JT, QT and QTc durations (all in ms), J and S amplitudes (both in mV), and QRS and T axes (both in °). ECG evaluations also included b-angles (in °) and duration of the base of a triangle (DBT) at 0.5 mV from the r' (in ms) in right precordial leads (V1, V2, V1ic3, V2ic3). Diagnostic type-1 ECGs were uncovered in 345 subjects and 1047 subjects had a negative test. Patients with BrS had significantly more atrial and ventricular conduction abnormalities (P, PR, QRS, and S duration) at baseline; these differences, except in PR duration, were aggravated upon ajmaline administration. In particular, the b-angle (e.g., V1: 28° [20; 46.5] versus 18° [12; 24], p<0.01) and DBT (e.g., V1: 130 ms [89; 214] versus 65 ms [42; 92.3], p<0.01) were significantly larger at baseline in patients with BrS, however, only with modest diagnostic value (area-under-the-curve 0.67–0.80). The optimal b-angle cut-off value based on the ROC curves to rule out BrS was determined at an angle of >15°, negative predictive values ranged from 78.6–95.5 and sensitivities ranged from 80–98.1% among different leads. Patients with BrS show more baseline ECG abnormalities and display more conduction slowing upon ajmaline infusion. The b-angle and DBT do not demonstrate strong enough diagnostic characteristics to serve as a stand-alone diagnostic tool. Drug provocation tests remain necessary for diagnosing BrS in patients without a spontaneous type-1 ECG. Type of funding source: None