<![CDATA[Background: Electrocardiographic markers, including the r′-wave triangle base duration and beta-angle, have been proposed as adjunctive indicators of Brugada syndrome (BrS). As flecainide challenge testing (FCT) carries potential risks, baseline ECG predictors may refine pre-test risk stratification, although their relationship with oral flecainide challenge positivity remains uncertain.Objective: To evaluate whether baseline r′-wave triangle base duration and beta-angle were associated with FCT positivity.Methods: This retrospective, single-center review included consecutive patients who underwent oral flecainide challenge within a historical institutional diagnostic pathway between September 2023 and September 2025. Baseline right-precordial ECG measurements, including r′-wave triangle base duration and beta-angle, were obtained from archived standard 12-lead tracings. The primary outcome was FCT positivity, defined as the emergence of a diagnostic type 1 Brugada patternResult: Among 40 included patients, 28 had a positive oral flecainide challenge result and 12 had a negative result. In exploratory analyses, larger baseline β-angle and longer r′-wave triangle base duration were associated with oral flecainide challenge positivity. Mean β-angle was 36.07° ± 15.86° in positive versus 21.83° ± 10.72° in negative challenges (p=0.007); mean r′-wave triangle base duration was 161.6 ± 92.8 ms versus 81.6 ± 38.0 ms, respectively (p<0.001). ROC analysis showed moderate discriminatory performance (AUC 0.756 for β-angle, 0.769 for r′-wave). Sample-derived thresholds of 27.5° and 2.625 mm (105 ms) yielded sensitivity of 71.4% and specificity of 83.3%. A combined model incorporating both parameters showed an AUC of 0.780 (95% CI, 0.635–0.924), with 75.0% sensitivity and 83.3% specificity at the Youden-optimal threshold. Conclusion: Baseline r′-wave triangle base duration and beta-angle were associated with FCT positivity. These findings support further prospective investigation using standardized ECG acquisition and contemporary provocation protocols.]]>
