Pathophysiology and Natural History Myocardial Blood Flow

The functional significance of coronary collateral flow from a nonobstructed supply artery was studied in 121 patients with severe (>80%) single-vessel disease, 64 with and 57 without Q wave infarction. All patients underwent exercise thallium imaging and coronary angiography. On angiography, collateral flow was present in 85% of 74 occluded arteries compared with only 17% of 47 arteries with subtotal obstruction (p < .001). Collateral flow was not seen in arteries with lesions of less than 90% obstruction. Collateral flow was present in 100% of 29 occluded arteries in patients without Q wave infarction compared with only 76% of 45 occluded arteries with Q wave infarction (p < .005). Clinical variables did not correlate with collateral flow. Collateral flow did not prevent ischemia on exercise thallium imaging in patients without Q wave infarction: 30 of 33 (9 1%) with collateral flow had reversible thallium defects compared with 24 of 24 (100%) without collateral flow (p = NS). In patients with Q wave infarction, partially reversible exercise thallium defects (peri-infarctional ischemia) were more common with flow to the area from either subtotal obstruction (73%) or collateral flow (45%) than with no flow from total occlusion (27%; p = .05). In patients with severe single-vessel disease the presence of collateral flow is principally determined by coronary occlusion. Collateral flow may protect from Q wave infarction but does not prevent exercise ischemia on thallium imaging. Circulation 71, No. 4, 681-686, 1985. THE FUNCTIONAL significance of coronary collateral vessels visualized at angiography remains controversial, despite a large number of studies.'-" These studies have produced conflicting findings as to whether collateral blood flow protects the myocardium from exercise-induced ischemia, varying from complete or partial protection' to no protection or an increased incidence of ischemia.t'1 Differences in patient selection and methodology may explain some of these discrepancies. Most studies were in patients with multivessel disease, making it difficult to distinguish between ischemia in the distribution of the collateralized and the noncollateralized vessel and introducing the variable effect of obstruction in the vessel supplying collaterals. From the Hallstrom Institute of Cardiology and the Department of Nuclear Medicine, Royal Prince Alfred Hospital, Sydney, Australia. Supported by grants from the National Heart Foundation of Australia and the Postgraduate Foundation of the University of Sydney. Address for correspondence: S. B. Freedman, M.B., Ph.D., Hallstrom Institute of Cardiology, Royal Prince Alfred Hospital, Camperdown, N.S.W. 2050, Australia. Received Sept.10, 1984; revision accepted Jan. 3, 1985. In this study we selected patients with severe obstruction in only one major coronary artery so that the functional significance of collateral blood flow could be assessed without the interference of ischemia in another area or obstruction in the vessel supplying collaterals.