Abstract 2714: Electrophysiological Characteristics in Idiopathic Ventricular Fibrillation Compared to Brugada Syndrome
Background: Idiopathic ventricular fibrillation (IVF) is a rare but fatal tachyarrhythmia that occurs in patients without structural and electrophysiological abnormality. A steeply sloped action potential duration restitution (APDR) curve and conduction delay are known to be important determinant in the development of ventricular fibrillation (VF). However, APDR properties and conduction delay have not been well examined in idiopathic ventricular fibrillation (IVF) patients.
Methods: Endocardial monophasic action potential (MAP) was obtained from 7 IVF, 39 BrS patients and 9 control subjects. MAP duration at 90% repolarization and maximum slope of the APDR curve were obtained at right ventricular apex (RVA) and at right ventricular outflow tract (RVOT) by pacing. The dispersion of the APDR curve was defined as a difference of the maximum slope of APDR curves of two recording sites. We also examined relative refractory period (RRP) as a marker of conduction delay.
Results: Maximum slope of the APDR curve in IVF or BrS patients was significantly (p < 0.05) steeper than that in controls at both RVA and RVOT (IVF vs. BrS vs. control; 0.93 vs. 0.98 vs. 0.62 at RVA, 0.87 vs. 0.77 vs. 0.58 at RVOT). The dispersion of maximum slope of the APDR curve was significantly higher in IVF or BrS patients than that in controls (0.32 vs. 0.34 vs. 0.11). RRP between RV in IVF or BrS patients was significantly longer than that in controls (263 vs. 256 vs. 243 ms from RVOT to RVA, 257 vs. 251 vs. 241 ms from RVA to RVOT). There were no significant differences in maximum slope of the APDR curve, dispersion of maximum slope of the APDR curve and RRP between IVF and BrS patients. However, no IVF patients showed positive late potential, but it was very frequently (77%, p < 0.01) found in BrS patients. VF was not induced in any IVF patients by programmed electrical stimulation, but it was induced in 60% of BrS patients (p < 0.01).
Conclusions: The steeply sloped APDR properties and longer RRP, which indicate spatial and temporal heterogeneity of APD, may be only abnormality in IVF patients, unlike BrS patients.