Abstract 2252: Action Potential Duration Restitution Property and Conduction Delay in Brugada Syndrome
Background: Steeply sloped action potential duration (APD) restitution curves (>1.0) are known to be associated with complex unstable dynamics, leading to conduction blocks, wave breakups and ventricular fibrillation (VF). Higher spatial heterogeneities of APD restitution curve and conduction delay (CD) are also known to be important determinant in the induction of VF. However, APD restitution properties and CD have not been well examined in Brugada syndrome (BS) patients. We demonstrate the APD restitution properties and CD in BS patients.
Methods: Endocardial monophasic action potentials (MAPs) were obtained from 25 BS patients (mean age: 44.6 years) and 10 control patients (mean age: 50.4 years) using the contact electrode method. MAP duration at 90% repolarization (MAPD90), effective refractory periods (ERP) and the maximum slope of APD restitution curve by delivering a single extra-stimulus (S2) at a basic cycle length of 500 ms (S1) were obtained at right ventricular apex (RVA) and right ventricular outflow tract (RVOT). The dispersion of APD restitution curve was defined as a difference of the maximum slope of APD restitution curve between RVA and RVOT. We also examined a relative refractory period (RRP) which was recognized as S1–S2 interval at the onset of conduction delay from pacing site to another right ventricular site (from RVOT to RVA or from RVA to RVOT).
Results: There was no difference in MAPD90 and ERP between BS and control. However, the maximum slope of APD restitution curve in BS was significantly steeper than control at both RVA and RVOT (BS vs. control: 1.14 ± 0.41 vs. 0.67 ± 0.24 at RVA, p < 0.05, 1.11 ± 0.34 vs. 0.74 ± 0.20 at RVOT, p < 0.05). The dispersion of APD restitution curve was also higher in BS than control (BS vs. control: 0.66 ± 0.24 vs. 0.36 ± 0.13, p < 0.05). The RRP was significantly longer in BS than control from RVOT to RVA (BS vs. control: 257 ± 13 ms vs. 247 ± 11 ms, p < 0.05), but not from RVA to RVOT.
Conclusions: The steeply sloped APD restitution properties, the higher dispersion of the maximum slope of APD restitution curve and longer RRP were observed in BS. This abnormal restitution property and CD would be related to the development of VF in BS.