Because of abnormal repolarization, the T waves will become inverted and the ST segment will become depressed at least 1 mm below the baseline. Myocardial ischemia is reversible, but if it continues, myocardial injury results. Myocardial injury is reversible, but it indicates ongoing ischemia consistent with a coronary artery occlusion. Without prompt intervention, an MI may occur. Because the injured cells can't depolarize or repolarize fully, you'll see the ST segment elevate at least 1 mm above the baseline in the leads that monitor the area of occlusion.
Myocardial infarction occurs when one or more coronary arteries are completely occluded.
ST-segment elevation in the leads monitoring the area of myocardial ischemia. Because infarction interferes with ventricular repolarization, ST-segment elevation occurs within the first few seconds of occlusion. Appearance of a Q wave within a few hours to a few days after the occlusion if all three layers of the myocardium have been affected. Necrotic tissue can't conduct electricity, so the current moves away from the area, resulting in a negative waveform. Changes are subtle, if they exist at all.