A Classification of Unstable Angina Revisited | Circulation
The 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.
Table 2 Braunwald classification of unstable angina from 1989
The Braunwald Classification of unstable angina pectoris (UAP) stratifies patients according to both the type of anginal pain and the underlying cause of the pain. Increasing class is associated with increasing risk of both recurrent ischemia and death at 6 months.
Patients with unstable angina are heterogeneous with respect to presentation, coronary artery morphology, and clinical outcome. Subclassification of these patients based on clinical history has been proposed as a means of identifying individuals at increased cardiac risk. We applied such a classification system to 129 patients discharged from a coronary care unit with a diagnosis of acute myocardial ischemia. Patients were then assessed for cardiac events (recurrent angina requiring revascularization, myocardial infarction, death) 12 months following hospital discharge. Patients were classified as recent onset unstable angina preinfarction (n = 42), crescendo unstable angina preinfarction (n = 48), and unstable angina postinfarction (n = 39). Within each of these groups, the patients were further subclassified based on the occurrence of angina on effort, at rest, or both. No attempt was made to subset patients taking antiischemic drugs at the time of clinical presentation to the physician. Coronary angiographic pathology (morphology and number of vessels involved) was similar in the subgroups, but coronary artery thrombus was statistically more likely to be found in patients with crescendo rest angina preinfarction or with frequent anginal episodes at rest postinfarction. Mortality was significantly higher for patients with unstable angina postinfarction (7.7%) than preinfarction (1.1%). No statistical differences were noted between the subgroups with respect to the occurrence of myocardial infarction or recurrent unstable angina requiring revascularization. These data suggest that subclassification of unstable angina patients based on clinical characteristics at presentation is not useful to predict subsequent myocardial infarction or recurrent angina requiring revascularization. However, as one might expect, patients with recurrent angina postinfarction have a higher mortality rate than patients with unstable angina preinfarction, and patients with recurrent rest angina, either pre‐ or postinfarction, are more likely to have intracoronary thrombus than patients with new onset angina or crescendo effort angina; however, the presence of thrombus did not predict a poor clinical outcome.
It has long been recognized that coronary artery disease comprises a wide spectrum of conditions, ranging from chronic stable angina to acute myocardial infarction. Unstable angina, in the middle of this spectrum is a heterogeneous syndrome with widely variable symptoms and prognosis. In 1989, a classification of unstable angina was introduced ; this classification is based on the clinical history (accelerated exertional angina or rest pain, the timing of the latter in respect to presentation, and the clinical circumstances in which unstable angina developed), on the presence or absence of ECG changes, and on the intensity of anti-ischemic therapy.