In order to investigate myocardial action potential propagation under ischemia and infarction, we present a modified version of the Luo-Rudy I model. The chosen domain is a 2D virtual heterogeneous sheet of myocardial tissue, subdivided in three distinct zones: an ischemic area (CZ), a border zone (BZ, linear transition between physiological and ischemic values) and normal tissue (NZ). Ischemia is simulated through hyperkalemia and acidosis and affected parameters are changed in the CZ and in the BZ at each time after the onset of ischemia. We study how the interaction between propagating waves and ischemic regions can lead to the onset of cardiac arrhythmias, including ventricular tachycardia (VT) and fibrillation (VF). We investigate pinning and unpinning of rotating waves to and from infarction zones using pulsed electric fields. We will present an example of an interesting dynamics leading the system from a chaotic transient to long-lasting spirals pinned to ischemic heterogeneities.