Effects of dipyridamole-induced vasodilation on myocardial uptake and clearance kinetics of thallium-201

Abstract

Myocardial thallium-201 (201Tl) uptake and clearance after intravenous administration of dipyridamole (150 μg/kg) were determined in 12 open-chest anesthetized dogs with a partial coronary artery stenosis. 201Tl (1.5 mCi) was injected intravenously and myocardial biopsy specimens were obtained 10 min, 60 min, and 2 hr after injection. Serial changes in 201Tl activity in the normal zone and in the zone of partial stenosis were correlated with microsphere-determined regional blood flow and distal coronary pressure. Another 9 dogs with equivalent stenosis not given dipyridamole before 201Tl served as controls. In the 12 dogs given dipyridamole, 201Tl activity at 10 min in the zone of stenosis was reduced to 42 ± 5% of initial normal zone activity (p