[Unstable angina pectoris: definition, pathology, clinical course].

Unstable angina pectoris signifies an ischemic heart condition intermediate between chronic stable angina and acute myocardial infarction. Numerous descriptive terms have been used and therefore a definition has been selected which helps in making therapeutic decisions. The cause of instability may be either a fixed coronary lesion or probably more often, dynamic events such as spasm. The course under medical treatment appears to be better than is commonly thought.