Unstable angina and non-ST segment elevation myocardial infarction (acute coronary syndromes)

Approximately 8 million patients present annually to the emergency room with symptoms of acute chest pain. Of these, 2 million turn out to have a cardiac cause resulting in hospitalization. Fewer than 10% of these patients have ST segment elevation on the electrocardiogram (1). Since the diagnostic sensitivity and specificity of the electrocardiogram are poor in this setting, there is a strong impetus for effective emergency room stratification. The spectrum of acute coronary syndromes includes unstable angina and non-ST segment elevation myocardial infarction as the clinical presentations. The distinction between these syndromes is usually made retrospectively based on biochemical markers, and hence, initial treatment strategies are identical. The diagnosis of primary unstable angina excludes external factors that may exacerbate the symptoms of coronary ischemia, such as severe anemia, thyrotoxicosis, and tachyarrhythmias.