Predictors of non-Q-wave acute myocardial infarction in patients with acute ischemic syndromes: An analysis from the thrombolysis in myocardial ischemia (TIMI) III trials

Among patients with acute ischemic syndromes, patients with non-Q-wave acute myocardial infarction (AMI) are known to be at higher risk for death, reinfarction, and other morbidity than those with unstable angina. The aim of this study was to develop a clinically useful prediction rule to assist in distinguishing, at the time of presentation, patients with non-Q-wave AMI from those with unstable angina. The TIMI IIIB trial enrolled 1,473 patients presenting with ischemic pain at rest within 24 hours who had either electrocardiographic changes or documented coronary artery disease. Non-Q-wave AMI on presentation was documented by elevation of creatine kinase-MB in 33% of patients. Fifty clinical and electrocardiographic variables were compared between the patients with non-Q-wave AMI and unstable angina. After performing logistic regression, 4 baseline characteristics independently predicted non-Q-wave myocardial AMI: the absence of prior coronary angioplasty (odds ratio [OR] = 3.3, p < 0.001), duration of pain ≥60 minutes (OR = 2.9, p < 0.001), ST-segment deviation on the qualifying electrocardiogram (OR = 2.0, p < 0.001), and recent-onset angina (OR = 1.7, p = 0.002). Using these 4 characteristics, a prediction rule for non-Q-wave AMI was developed. For the entire cohort of patients in TIMI III, the percentages of patients with non-Q-wave AMI when 0, 1, 2,3, and 4 risk factors were present were 7.0%, 19.6%, 24.4%, 49.9%, and 70.6%, respectively (p < 0.001). Thus, easily identifiable characteristics at presentation can be used to assess the likelihood of non-Q-wave AMI.