Functional importance of coronary collateral vessels

Abstract

Angiographically demonstrable coronary collateral vessels are believed to preserve myocardial function at rest, but disagreement exists regarding the importance of collaterals in mitigating exercise-induced ischemic dysfunction. Therefore, we used radionuclide cineangiography during exercise to assess the left ventricular (LV) functional effects of collateral vessels in 125 patients with at least 1 major coronary artery that had ≥ 90% diameter stenosis but without prior myocardial infarction. Regional LV function, graded on a 4-point scale, worsened during exercise by at least 1 grade in 14 of 43 regions (33%) with good collaterals, and in 70 of 98 without good collaterals (p < 0.001). Of the 43 good collaterals, 14 were supplied by arteries with ≥ 75% stenoses; 10 of 14 regions (71%) thus supplied worsened by at least 1 grade (p < 0.01). The ischemia-mitigating effect of coronary collateral vessels also affected the magnitude of exercise-induced global dysfunction. Of 43 patients with only one ≥ 90% stenotic artery, 18 had good collaterals; in these patients, average LV ejection fraction (EF) at rest was 51 ± 8%; LVEF during exercise was 46 ± 7%. In the 25 patients without good collaterals, LVEF at rest was 52 ± 7%, and LVEF during exercise was 41 ± 9% (p < 0.005 vs good collaterals). Similar results were noted among the 32 patients with 2 arteries that had ≥ 90% stenoses, but in the 50 patients with all 3 arteries that had ≥ 90% stenoses, there was no difference in the magnitude of exercise-induced ischemic dysfunction between groups with 2, 1 or no good collaterals.