Simulation studies of the electrocardiogram. II. Ischemia and infarction.

Experimental studies of the myocardial action potentials following coronary artery occlusion have shown that the resulting regional ischemia is reflected by characteristics changes in the shapes of the action potentials in the ischemic region. The principal changes are decreases in the magnitude of the resting potential and in the action potential duration. Action potentials with prolonged durations have been observed in the infarcted regions of experimental animals after the development of inverted T waves in the surface electrocardiogram (ECG). We use such abnormal action potentials in our digital computer model to study the effects of acute myocardial ischemia and infarction on the surface ECG. The heart is represented in sufficient detail to allow variations in the location and size of the ischemic injury and in the distribution of the severity of injury within the injured region. The evolution of acute infarctions is simulated by progressively modifying the abnormal action potentials assigned to the injured region. Calculated standard 12 lead ECGs and torso isopotential surface maps for simulated acute ischemia and infarction are in good agreement with patient data reported in the literature. Typical simulations include anterior and inferior transmural ischemia and infarction and anterior subendocardial ischemia. The model is used to examine relationships between torso surface potentials during ventricular activation and recovery and the site and size of the ischemic injury.