Functional importance of coronary collateral vessels.

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 greater than or equal to 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 less than 0.001). Of the 43 good collaterals, 14 were supplied by arteries with greater than or equal to 75% stenoses; 10 of 14 regions (71%) thus supplied worsened by at least 1 grade (p less than 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 greater than or equal to 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 less than 0.005 vs good collaterals).(ABSTRACT TRUNCATED AT 250 WORDS)