1. Myocardial infarction occurs when blood flow decreases or stops to the heart muscle, depriving it of oxygen and causing cell death. 2. The ECG, blood tests of cardiac enzymes like troponin, and symptoms are used to diagnose a myocardial infarction. 3. Different coronary artery blockages can cause infarcts in specific heart regions, shown by distinct ST segment changes on ECG - inferior infarcts raise ST in II, III, AVF, etc.