Effect of coronary collateral circulation on regional myocardial perfusion assessed with quantitative thallium-201 scintigraphy

The functional role of the coronary collateral circulation in patients with coronary artery disease has yet to be clarified. Because the distribution of thallium in the myocardium after its intravenous injection is proportional to regional blood flow, quantitative thallium scintigraphy was employed to assess noninvasively the effect of collateral vessels on regional myocardial perfusion at rest and after exercise stress. Sixty-two patients with significant (greater than 50 percent stenosis of luminal diameter) coronary artery disease had after exercise thallium imaging and 35 patients underwent imaging at rest. Delayed redistribution images were obtained after exercise and at rest. Images were divided into six segments for analysis and interpreted using computer-assisted quantitative techniques. In patients undergoing exercise stress, collateral vessels did not significantly influence thallium uptake patterns in segments associated with electrocardiographic Q waves. In segments without Q waves, thallium uptake was more frequently abnormal (p <0.001) in segments with than in segments without collateral vessels whether or not such vessels were jeopardized. The presence or absence of collateral channels did not affect the frequency of occurrence of thallium redistribution. In patients undergoing serial imaging at rest, the prevalence of segments with normal thallium uptake was greater in segments with nonjeopardized than in those with jeopardized collateral vessels (p <0.05).It is concluded that (1) coronary collateral vessels are an indicator of severe coronary arterial obstruction and do not protect against exercise-induced hypoperfusion or affect the occurrence of redistribution, and (2) non-jeopardized collateral vessels appear to augment perfusion at rest in some segments to the degree that normal thallium uptake at rest is observed.