Intracellular recordings during VF: Role of ion channels from experiments and computer models

The authors have developed a method incorporating an isolated rabbit heart and a floating microelectrode which allows not only intracellular recordings during normal sinus rhythm (NSR) and ventricular fibrillation (VF), but also permits control over extracellular ion concentrations and the concentrations of drugs delivered to the heart. Using this method, they analyzed the maximum depolarization velocity during NSR, VF, and VF while perfusing with tetrodotoxin (VF/TTX). These results are compared with those obtained from a one-dimensional (1-D) propagation model of ventricular cells undergoing premature re-excitation and reduced sodium conductance. To better simulate reentrant activation analogous to VF, a 2-D model of coupled network of cells was constructed. The activity of sodium channels was inferred by analyzing the action potentials and sodium channel conductances generated by the 2-D model.