Unstable Coronary Syndromes

T he establishment of a prognosis and the approach to the treatment of many diseases is aided greatly by a logical classification. For example, classification of a wide variety of neoplasms by anatomic extent, microscopic appearance, and the presence of special markers now forms the basis for selecting appropriate therapy. In cardiology, the classification of patients with acute myocardial infarction and congestive heart failure has been of enormous value in following the progress and in selecting therapy of individual patients and in comparing the outcome of similar patients treated at different locations and at different times. The purpose of this article is to provide a classification of unstable angina. This classification is designed to facilitate communication about these patients, to aid in the decision regarding diagnostic measures and therapy of individual patients, and to provide a more precise basis for including patients in and for evaluating the outcome of clinical trials. Unstable angina is a complex condition. Early in this century, the clinical-pathologic features of two of the principal manifestations of ischemic heart disease-acute myocardial infarction and chronic stable angina-had already been well described. It has taken much longer to define a syndrome that is intermediate in severity between these two conditions. In 1923, Wearn' described, in a group of 19 patients with acute myocardial infarction confirmed at necropsy, attacks of angina pectoris that may precede myocardial infarction and serve as warnings of the presence of coronary artery disease. In 1937, Sampson and Eliaser2 and Feil3 separately described a syndrome consisting of severe, prolonged anginal pain that often led to acute myocardial infarction, and they termed it "impending acute myocardial infarction." Other terms that have been used for this condition include "preinfarction angina," "crescendo angina," "status anginosus,'" "accelerated angina," "acute coronary insufficiency," and