Enhanced regional left ventricular function after distant coronary bypass by means of improved collateral blood flow

To determine whether coronary artery bypass surgery can improve function in left ventricular regions not amenable to direct revascularization, 24 patients with multivessel coronary artery disease were studied by radionuclide angiography and coronary arteriography before and 6 months after coronary artery bypass surgery. All had proximal stenosis of the left circumflex artery or a major obtuse marginal branch. Left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors; the 8 sectors corresponding to the posterolateral free wall were used to assess function in the left circumflex artery distribution. Change in function in the left anterior descending territory was not analyzed because of the nonspecific septal hypokinesia that develops postoperatively. For the total group, coronary artery bypass surgery significantly increased both global left ventricular ejection fraction during exercise (43 ± 13% to 50 ± 14%, p < 0.001) and the change in ejection fraction from rest to exercise (-7 ± 10% to 0 ± 6%, p < 0.001). Such improvement was observed in 9 of 10 patients with all stenoses bypassed, and to an equivalent degree in 9 of 10 patients in whom the left circumflex artery either could not be bypassed or the bypass graft was occluded (but bypass grafts to other coronary arteries were patent). Similarly, regional ejection fraction in posterolateral segments during exercise also increased comparably after operation in patients with a patent (from 57 ± 18% to 70 ± 19%, p < 0.001) or nonpatent (from 51 ± 14% to 68 ± 14%, p < 0.001) left circumflex graft. In 8 of the 10 patients without patent left circumflex grafts, collateral perfusion to the posterolateral free wall from other bypassed arteries was demonstrated angiographically after surgery. In four patients in whom all grafts were occluded, regional and global left ventricular function during exercise was unchanged by surgery. These data suggest that many patients with a nonbypassable coronary artery may still benefit from coronary artery bypass surgery if the jeopardized myocardium is perfused by collateral vessels supplied by a stenosed artery amenable to bypass surgery.