Adaptation mechanisms during myocardial ischemia in chronic unstable angina pectoris

Unstable angina with a clinical duration of < 2 months is characterized angiographically by a high incidence of complex lesions. Some patients have ischemic rest pain syndromes of longer duration. Thus, we retrospectively analyzed, in blinded fashion, the clinical and angiographic findings in 52 patients with unstable angina of < 2 months' duration (group A), and compared the results with those of 32 patients with unstable angina of > 6 months' duration (group B). Group B had a greater number of diseased vessels and better collateral circulation, but had fewer eccentric lesions. There were no differences in age, left ventricular function, or history of prior myocardial infarction. Thus, chronic unstable angina is associated with more extensive coronary disease than unstable angina of shorter duration. The role of different anatomic substrata and collateral circulation is discussed.