FUNCTIONAL SIGNIFICANCE OF CORONARY COLLATERALS IN MAN

In 29 patients with coronary artery disease the functional significance of coronary collaterals was studied during surgery for aortocoronary bypass grafting. Poststenotic coronary pressure and postocclusion graft flow hyperemia were measured in 34 vessels receiving a coronary bypass graft. The vessels were divided into groups according to the angiographically determined degree of coronary stenosis: group I: stenosis up to 80%, group II: stenosis between 80 and 90%, group III: stenosis between 90 and 100%, Group IV: acute occlusion without visible collaterals and Group V: complete occlusions with collaterals. When a coronary stenosis surpasses 80% luminal narrowing it becomes hemodynamically significant: pressure gradient over the stenosis becomes significant and there appears a hyperemic response after graft occlusion. From group I to IV poststenotic coronary pressure decreases and graft flow hyperemia increases significantly (p<0.05). In all cases general coronary vasodilation was produced by intracoronary injection of dipyridamole. After vasodilation poststenotic coronary pressure decreased significantly (p<0.05) in groups I and II but not in III and IV. This indicates that there is still some increase in flow over the stenosis i.e. coronary reserve is not completely expended until 90% stenosis. Hyperemic graft flow response correlates well with poststenotic coronary pressure: the relation can be described by an asymptotic regression. This suggests that graft flow hyperemia is a reflection of compensatory peripheral vasodilation rather than a response to ischemia. In group V, i.e. complete chronic occlusions with collaterals, peripheral coronary pressure was 40.7±3.3% of systemic pressure and this value decreased significantly (p=0.002) to 34.0±2.6% after vasodilation. Hyperemic response was 1.57±0.07. These values are significantly different from groups I and IV, but not from II and III. These findings suggest that coronary collaterals restore coronary reserve partially. Nevertheless, a chronic coronary occlusion compensated by collaterals corresponds functionally to a 90% pure stenosis. © 1978 Dr. Dietrich Steinkopff Verlag.