Abnormal Action Potential Duration Restitution Property in the Right Ventricular Outflow Tract in Brugada Syndrome

Abstract

Background: Although patients with Brugada syndrome (BS) are at risk of ventricular fibrillation (VF) and ensuing death, the action potential duration (APD) restitution properties of the right ventricular outflow tract (RVOT) in patients with BS remain undetermined. Methods and Results: Endocardial monophasic action potentials (MAPs) were obtained from 16 patients with BS and 17 control patients. MAPs were recorded from the RVOT in all patients. The MAP duration at 90% repolarization (MAPD₉₀), effective refractory period (ERP), and maximum slope of the APD restitution curve were obtained. VF was induced with up to 3 extrastimuli from the RV apex or RVOT. There was no difference in MAPD₉₀ between the 2 groups, but the ERP was significantly shorter in patients with BS than in control patients (210.7±10.5 vs 223.8±13.4 ms, P=0.008). MAPD at the shortest diastolic interval was significantly shorter in patients with BS than in control patients (149.9±19.9 vs 179.8±13.7 ms, P<0.001). The maximum slope of the APD restitution curve was steeper in patients with BS than in control patients (2.90±1.29 vs 1.38±0.41, P<0.001). Conclusions: The shorter ERP, shorter MAPD at the shortest diastolic interval and steeply sloped APD restitution curve in the RVOT appear to be related to the inducibility of VF in patients with BS. (Circ J 2010; 74: 664-670)