Mechanisms of angina relief in patients after coronary artery bypass surgery.

Abstract

The mechanisms underlying the relief of angina after coronary bypass surgery were studied by analyzing the results of the baseline and follow-up treadmill tests on patients included in a prospective randomized study of surgical vs. medical treatment of stable angina pectoris. There were 22 surgically treated patients and 35 medically treated patients, whose endpoint on the initial treadmill tests was angina with concomitant ischemic ST depression. At 1 yr, 91% of the surgically treated patients had no chest pain during the exercise test while only 11% of the medically treated patients were free from angina (P < 0.001). Exercise tolerance was significantly better in both groups, but improvement was greater in the surgically treated patients (exercise tolerance increased by 98% compared with 28%). The product of heart rate and systolic blood pressure measured at the maximal exercise level increased significantly in the surgically treated patients; this product decreased slightly in the medically treated patients. Of the surgically treated patients, 59% had ischemic ST depression on the exercise ECG but did not develop anginal pain, compared with only 9% of the medically treated patients (P < 0.001). In addition to increased coronary blood flow, for which the increased product of heart rate and blood pressure is indirect evidence, trauma to nerves and possibly other nonspecific factors related to surgery may be important mechanisms contributing to the relief of angina after coronary bypass surgery.