Abnormal Atrial Action Potential Restitution and Increased Intraatrial Conduction Time Contribute to the Inducibility of Atrial Fibrillation in Brugada Syndrome

Abstract

Background: Brugada syndrome is often accompanied by atrial tachyarrhythmias, such as atrial fibrillation (AF). Mechanisms underlying the atrial arrhythmogenicity are unknown. Objective: To investigate atrial vulnerability in patients with Brugada syndrome. Methods: Two groups of patients were compared; 18 patients with Brugada syndrome (Brugada syndrome group) and 11 age-matched patients with neither structural heart disease nor AF episodes (control group). Programmed electrical stimulation was performed from the right atrium (RA), and the effective refractory period of the right atrium (ERP-RA), interatrial conduction time (IACT, conduction time from the pacing stimulus to the distal coronary sinus activation), monophasic action potentials (MAPs) at the high RA, and the inducibility of AF lasting > 30 seconds were compared. MAP duration at 80% repolarization (MAPD₈₀) was measured. Results: AF was induced with a single extrastimulus or double extrastimuli in all patients with Brugada syndrome but in none of the control patients. The ERP-RA did not differ between the two groups. IACT at the shortest diastolic interval was significantly increased in the Brugada syndrome group compared to that in the control group. The maximum slope of the MAPD₈₀ restitution curve was significantly steeper in the Brugada syndrome group than in the control group (2.4 ± 2.0 vs. 0.82 ± 0.36, P < 0.02). Ventricular fibrillation was induced with programmed ventricular stimulation in all Brugada syndrome patients. Conclusion: Both abnormal interatrial conduction and steep restitution of the atrial action potential duration may contribute to the atrial arrhythmogenicity in Brugada syndrome.