Non-Q-wave myocardial infarction: incidence, pathophysiology, and clinical course compared with Q-wave infarction.

Acute myocardial infarction can be stratified into electrocardiographic subsets based on the presence or absence of new Q waves. This stratification has important clinical and prognostic utility. Coronary angiography during acute non-Q-wave compared with Q-wave infarction shows much higher infarct-related artery patency rates (about 75 vs. 10%) and increased coronary collateralization. Culprit legion morphology in non-Q-wave infarction commonly is complex. The frequent demonstration of recurrent clinical ischemia, or residual thallium-201 uptake abnormalities, and metabolic activity on persistent emission tomography suggest the presence of viable myocardium in the distribution of the non-Q-wave infarction usually represents 20-25% of acute myocardial infarctions. The University of California San Diego Collaborative Postinfarction Database and other large studies have found non-Q-wave infarctions to be more common in patients with a history of previous infarction and congestive heart failure, although their mortality during acute hospitalization is lower. However, in long-term followup to one year and beyond, non-Q-wave infarct mortality rates equal those of Q-wave infarction. Patients at low early and late risk of mortality include those with a first infarction who are under age 70, whereas patients with evidence of residual ischemia postinfarction are at increased risk of events. It is interesting to speculate that the settings of unstable angina pectoris, non-Q-wave infarction, and perhaps the picture after thrombolysis for acute myocardial infarction, have pathophysiologic similarities which may carry implications for future research and therapy.