Abstract 18147: Diagnosing Brugada Syndrome in Absence of Electrocardiographic Pattern: Predictive Modeling of Activation Delay in the Right Ventricular Outflow Tract

Introduction: Diagnosing Brugada Syndrome(BrS)involves detecting the type1 ECG pattern, spontaneously or drug-induced, which can be challenging(concomitant diseases, ECG phenocopies, unavailability of pharmacological agents, hypersensitivity). Intrinsic cellular changes that cause ECG abnormalities are mainly located in the right ventricular outflow tract(RVOT).

Hypothesis: Comparing the activation time(AT)delay between the RVOT and the anterior right ventricle(RVa)in subjects with BrS(with concealed or manifested pattern 1) vs normal controls may provide a cut-off value for a new diagnostic method.

Methods: Seventy-five participants(mean age 46±24 y; 45 men), 57 BrS, 10 healthy controls, and 8 RBBB patients, underwent ECGI and ECG recordings. Concealed BrS patients underwent an ajmaline infusion to be studied both in the absence and presence of pattern1. Ventricular epicardium has been divided into 8regions and the mean activation time(ATM)has been calculated for each region. The ATMs were normalized to QRS length (ATM%) and compared across populations.

Results: Analysis of ATMs% in RVa did not show differences between groups. Instead, analysis of ATM and ATM% in RVOT, showed significant differences between controls and BrS both with concealed or manifested ECG pattern1 (37.2±6.23vs68.33±14.73 ms, p<0.001; 37.2±6.23vs107.6±21.16 ms, p<0.001). By setting the true negative (controls) and true positive (BrS) populations, the diagnostic performance tests were done: a 45% increase in RVa ATM was the best predictor of delayed RVOT activation in BrS (AUC=0.97,Accuracy=0.92,F-score=0.95). In patients with RBBB the increase between RVa and RVOT remained below the cut-off of 45%

Conclusions: In BrS, patients exhibit a pathological delay in the AT of the RVOT, considered significant if it exceeds 45% of the ATM in the RVa. It could be used as alternative diagnostic method when the conventional approach is inconclusive or the ECG pattern is not manifested.