The diagnosis of myocardial infarction requires enzyme confirmation if we are to separate anginal syndromes from coronary disorders involving necrosis of myocardial tissue. Patients with a first myocardial infarction are more homogeneous in their risk profile and are more accurately categorized into different electrocardiographic subsets than are patients with prior infarctions. The electrocardiogram has been used to classify two types of myocardial infarction—the Q-wave (transmural) infarction, with the implication that a Q wave represents through-and-through endocardial-to-epicardial necrosis, and the non—Q-wave (nontransmural) infarction, with the implication that the absence of a Q wave indicates less extensive myocardial damage and possibly an increased potential for recurrent coronary events.
See also p 1545.
Non—Q-wave myocardial infarction is a heterogeneous group of disorders and includes true posterior transmural ("Q-wave") infarctions without manifest Q waves on the scalar 12-lead electrocardiogram, subendocardial infarctions with transient ST-wave and T-wave changes, intramural infarctions with giant negative T waves