Unstable angina: pathogenetic mechanisms, coronary angiographic observations, risk stratification, and therapeutic implications.
The acute coronary syndromes, which include unstable angina (UA) and non-Q-wave (NQMI) and Q wave myocardial infarction (MI), constitute the most frequent acute clinical manifestations of coronary artery disease. Unstable angina and NQMI are clinically distinct syndromes of acute ischemia, implying the presence of further jeopardized myocardium. Regardless of whether a small degree of myocardial necrosis has occurred (as measured by the release of creatine kinase and MB isoenzyme in the blood), both diagnoses have in common the likely potential for recurrent angina and infarction. Hence, these entities uniquely suggest the possibility of further hazard rather than the necessity of accepting and managing the consequences of loss of function. The appropriate diagnostic and therapeutic approaches are governed by these characteristics. Only during the last 15 years has coronary angiography been routinely performed in patients with acutely unstable coronary syndromes. This has led to the subsequent development of new insights into pathogenesis. In addition, new treatment modalities are now available.