Acute non-Q-wave myocardial infarction: a distinct clinical entity of increasing importance.

Despite the increasing incidence of acute non-Q-wave myocardial infarction, controversy remains regarding its validity as a distinct pathophysiologic physiologic and clinical entity. Review of the data indicates that the controversy is more apparent than real. The pathophysiologic factor discriminating best between non-Q-wave and Q-wave infarction is the incidence rate of total occlusion of the infarct-related artery, approximately 30% in non-Q-wave infarction and 80% in Q-wave infarction. Patients with non-Q-wave infarction have a higher incidence of pre-existing angina than patients with Q-wave infarction; they also have lower peak creatine kinase levels, higher ejection fractions and lower wall-motion abnormality scores, which suggests a smaller area of acute infarction damage. However, patients with non-Q-wave infarction have a significantly shorter time to peak creatine kinase level and more heterogeneous ventriculographic and electrocardiographic infarct patterns. The in-hospital death rate is lower in non-Q-wave than in Q-wave infarction (approximately 12% v. 19%). The long-term death rates are similar for the two groups (27% and 23%), but the incidence of subsequent coronary events is higher among patients with non-Q-wave infarction; in particular, reinfarction is an important predictor of risk of death. Most of the differences in biologic and clinical variables between the two types of acute infarction can be related to a lower incidence of total occlusion, earlier reperfusion or better collateral supply in non-Q-wave infarction. Further study is needed to better characterize the long-term risk and to define the most appropriate therapies.