 Myocardial infarction the term acute myocardial infarctionAMI should be used when there is evidence of myocardial injury defined as an elevation of cardiac troponin values with at least one value above the 99th percentile upper reference limit with necrosis in a clinical setting consistent with myocardial ischemia . Myocardial infarction is classified as either : ST elevation acute myocardial infarction. non-ST segment elevation acute myocardial infarction. according to the electrocardiogram at the time of admission. 