Collateral circulation in patients with unstable angina

Coronary collaterals were evaluated in 218 consecutive catheterized patients with unstable angina (defined as ischemic cardiac pain at rest associated with transient electrocardiographic changes). Collaterals were present in 106 patients (49 percent). The presence of collaterals correlated with the extent and severity of the coronary artery disease but not with age-, sex-, or risk factors. Among patients with comparable severity of narrowings, the presence of collaterals did not appear to protect against abnormal wall motion or pathologic Q waves on the ECG. In patients with single vessel disease, collaterals also did not appear to protect against transient ST segment elevation during ischemia.