Effect of aorto-coronary grafts and native vessel patency on the occurrence of angina pectoris after coronary bypass surgery.

Exercise testing of 52 patients on average 11 months after coronary bypass surgery for the relief of angina pectoris disclosed improvement in total work (P is less than 0.001), maximal tolerated load (P is smaller than 0.001), maximal heart rate (P is smaller than 0.01), and reduction of maximal ST segment depression (P is smaller than 0.001) in a group of 36 patients with all grafts patent. In another group of 16 patients with one or more grafts occluded the only significant change was a reduction in the maximal ST segment depression (P is smaller than 0.01). Early and late postoperative angiograms showed that 75 per cent of the grafts that became occluded were already closed a few weeks after operation. Occluded grafts were accompanied by persistence of collaterals, which disappeared or dimished in the majority of patients with patent grafts. Progression in native vessel lesions occurred in 40 per cent of patients. It was related to the grafting procedure (P is smaller than 0.01) but not to the state of grafts. The change in native vessels and other variables studied was equal in the patent and occluded graft groups, justifying the conclusion that graft patency was the major factor alleviating angina after operation.