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BACKGROUND The prevalence and significance of structural abnormalities in Brugada syndrome (BrS) are still largely debated. OBJECTIVES The authors investigated the relationship between genetic background, electroanatomic abnormalities, and pathologic substrate in BrS. METHODS They performed 3-dimensional electroanatomic unipolar and bipolar mapping in 30 patients with BrS. Twenty patients underwent 3-dimensional electroanatomic unipolar and bipolar mapping-guided right ventricular outflow tract (RVOT) endomyocardial biopsy. Programmed ventricular stimulation and genetic analysis were performed in all patients. RESULTS Low-voltage areas (LVAs) were observed at unipolar map in 93% of patients and at bipolar map in 50% of cases. Unipolar LVAs were always larger than bipolar LVAs, were always colocalized, and in all cases included RVOT. Disease-causing mutations were detected in 10 (33%) patients. Programmed ventricular stimulation was positive in 16 cases (53%). In 75% of patients, RVOT histology showed pathologic findings with myocardial inflammation in 80% of them. Among patients with abnormal bipolar map submitted to endomyocardial biopsy, 9 (81%) showed evidence of myocardial inflammation. Conversely, bipolar map was abnormal in 83% of patients with myocardial inflammation. Myocardial inflammation was also more prevalent among inducible patients (83% vs. 25% in noninducible; p = 0.032). CONCLUSIONS BrS is characterized by electroanatomical and structural abnormalities localized to RVOT with a gradient of the pathologic substrate from epicardium to endocardium possibly driven by myocardial inflammation. These findings reclassify BrS as a combination of structural and electrical defects opening the way to new risk stratification and therapeutic strategies.