Modeling the Human Heart Under Acute Ischemia

Ventricular tachycardia and ventricular fibrillation are known to be two types of cardiac arrhythmias that usually take place during acute ischemia and frequently lead to sudden death. In this work, a methodology for the in-silico study of the regionally acute ischemic heart is presented. The chapter describes the mathematical formulation of the electrophysiology of the heart. A numerical scheme for the efficient numerical solution of the mathematical problem is also given. Along with the mathematical basis for the solution of the electrophysiology problem, the highly electrophysiological detailed action potential model for human proposed by ten Tusscher (Am J Physiol Heart Circ Physiol 291:1088–1100, 2006) has been adapted to make it suitable for modeling ischemic conditions (hyperkalemia, hipoxia, and acidic conditions). At this step, a formulation of the ATP-sensitive K+ current has been introduced into the existing model and the resulting model has been subjected to ischemic conditions. The results show that the three components of ischemia decrease the action potential duration (APD) as well as the conduction velocity, while effective refractory period (ERP) depicts a non-monotonic behavior. The modified action potential model was implemented on a 3-D geometrically and anatomically accurate regionally ischemic human heart. The ischemic region was located in the anterior side of the left ventricle mimicking the occlusion of the circumflex artery. Realistic heterogeneity and fiber anisotropy were considered in the model. The model predicts the generation of figure-of-eight re-entries which cross the central ischemic zone formed in the epicardial surface due to the longer refractory period of the midmyocardial layers. Also, focal activity experimentally observed in the epicardium caused by re-entrant wavefronts propagating in the mid-myocardium that re-emerge in the heart surface was found in the simulations.