Dipyridamole Thallium for Evaluating Coronary Artery Disease

Dipyridamole [2,6-bis(diethanolamino)-4,8-dipyperidne-pyrimido-(5,4-d)pyrimidine] was initially studied in the 1950s as a synthetic compound that produces coronary vasodilatation. Dipyridamole was initially studied as an antianginal agent that did not increase myocardial oxygen consumption. Early reports by Bretschneider and co-workers1 noted an increase in coronary blood flow from 200% to 400% in anesthetized dogs without an increase in cardiac output. Other studies2 supported this but noted a lesser increase in coronary blood flow of only 30% to 90% with a decrease in blood pressure of 20 mm Hg and an associated increase in heart rate after injection of dipyridamole.