Vulnerability in regionally ischemic human heart. Effect of the extracellular potassium concentration

Ventricular tachycardia and ventricular fibrillation are two types of cardiac arrhythmias that usually occur during acute ischemia and frequently lead to sudden death. Pro-arrhythmic mechanisms related to acute ischemia have been extensively investigated, although often in animal models rather than in human. In this work, we investigate how hyperkalemia affects the vulnerable window to reentry and the reentry patterns in the heterogeneous substrate caused by acute regional ischemia using an anatomically and biophysically detailed human biventricular model. The ischemic region was located in the inferolateral and posterior side of the left ventricle, mimicking the occlusion of the circumflex artery, and includes a wash-out zone not affected by ischemia located in the endocardium. Realistic heterogeneity and fiber anisotropy have been considered in the model. An electrophysiologically detailed human action potential model has been modified to simulate ischemic conditions. The model predicts the generation of sustained reentrant activity in the form of single and double circuits around an area of block within the ischemic zone for K+ concentrations below 9 mM, with the reentrant activity corresponding to ventricular tachycardia in all cases. Our results also suggest that the wash-out zone is a potential pro-arrhythmic factor that favors sustained ventricular tachycardia.