Subendocardial infarct is an area of damaged and necrotic tissue on the innermost layer of the ventricle. Subendocardial infarct can result if subendocardial ischemia is allowed to persist without treatment. It can also be the result of a stenotic lesion in the associated coronary artery. Subendocardial infarct is not relieved with nitroglycerin, and the associated changes seen in the electrocardiogram do not revert to normal baseline.
The most notable ECG change is a persistent S-T segment depression. Subendocardial infarct affects ventricular repolarization, resulting in an S-T - T complex being seen without depolarization.