Idiopathic Ventricular Fibrillation Characterized by Spatial Heterogeneity of Action Potential Duration and Its Restitution Kinetics

Abstract

A 44-year-old man who had suffered multiple episodes of syncope presented with ventricular fibrillation (VF). Structural heart disease was ruled out. Programmed stimulation induced VF at the right ventricular apex (RVA) but not at the outflow tract (RVOT). Monophasic action potential duration (MAPD) at a basic cycle length of 400 msec was shorter at the RVA than at the RVOT (208 versus 231 ms). The maximum slope of the MAPD restitution curve at the 400-msec cycle length was much steeper at the RVA than at the RVOT (1.4 versus 1.0). Such spatial heterogeneity of the MAPD and of its restitution may facilitate wavebreak and functional reentry, predisposing to VF.