A model study of defibrillation of cardiac tissue

ImplantabIe cardioverter defibrillators (ICD´s) have gained widespread acceptance as an important tool in the prevention of sudden cardiac death. We believe that the development of the next generation of ICD´s will require a deeper understanding of the basic electrophysiological mechanisms by which an extracellular current stimulates recovered tissue, and affects the action potential of depolarized cells. To this end, we implemented a bidomain model of cardiac tissue using a Luo-Rudy model to describe the ionic current. The model was used to examine the effects of defibrillation shocks on cardiac action potential duration. We found that cathodal shocks were most efficacious at prolonging action potential duration (APD), biphasic shocks also prolonged APD, and anodal shocks prolonged or reduced APD depending on the S₁-S₂ coupling interval