Spatiotemporal differences in precordial electrocardiographic amplitude before and after flecainide provocation are associated with a history of unstable ventricular arrhythmia in Brugada syndrome

Introduction: A drug provocation test (DPT) is important for the diagnosis of Brugada syndrome (BrS). The link, however, between dynamic changes of electrocardiography (ECG) features after DPT and unstable ventricular arrhythmia (VA) in BrS remains unknown. Methods: Between 2014 and 2019, we assessed 27 patients with BrS (median age: 37.0 [interquartile range, IQR: 22.0–51.0] years; 25 men), including 9 (33.3%) with a history of unstable VA and 18 (66.7%) without. All patients in the study presented with Brugada-like ECG features before DPT. The ECG parameters and dynamic changes (∆) in 12-lead ECGs recorded from the second, third, and fourth intercostal spaces (ICS) before and at 1, 6, 12, 18, and 24 h after DPT (oral flecainide 400 mg) were analyzed. Results: The total amplitude of V₁ at the third ICS 18 and 24 h after DPT was significantly lower in patients with a history of unstable VA than in those without. Patients with BrS and unstable VAs had a significantly larger ∆ amplitude of V₁ at the second ICS 12 h after DPT than in those without unstable VAs (0.28 [0.18–0.41] mV vs. 0.08 [0.01–0.15] mV, p =.01). A multivariate analysis revealed that the amplitude of V₁ at the third ICS 18 and 24 h after DPT and the ∆ amplitude of V₁ at the second ICS 12 h after DPT were associated with a history of unstable VA. Conclusion: Nonuniform changes and spatiotemporal differences in precordial ECG features after DPT were observed in patients with BrS and these may be surrogate markers for risk stratification.