COMPARISON OF CORONARY VASODILATION WITH INTRAVENOUS DIPYRIDAMOLE AND ADENOSINE

Although both intravenous dipyridamole and adenosine have been used to produce coronary vasodilation during cardiac imaging, the relative potency of the commonly administered doses of these agents has not been evaluated. Accordingly, the coronary and systemic hemodynamic effects of intravenous adenosine (140-mu-g/kg per min) and intravenous dipyridamole (0.56 mg/kg over 4 min) were compared with a maximally dilating dose of intracoronary papaverine in 15 patients. Coronary blood flow responses were assessed using a Doppler catheter in a nonstenotic coronary artery. The protocol was discontinued in two patients because of transient asymptomatic atrioventricular (AV) block during adenosine infusion. The mean heart rate increased more with adenosine (11 +/- 9 beats/min) and dipyridamole (11 +/- 7 beats/min) than with papaverine (4 +/- 3 beats/min, p < 0.05 vs. adenosine and papaverine). The mean arterial pressure decreased less with dipyridamole (-10 +/- 3 mm Hg) and papaverine (-9 +/- 4 mm Hg) than with adenosine (-16 +/- 5 mm Hg, p < 0.01 vs. dipyridamole and papaverine). The peak/rest coronary blood flow velocity ratio was greater with papaverine (3.9 +/- 1.1) than with adenosine (3.4 +/- 1.2, p less-than-or-equal-to 0.05 vs. papaverine) or dipyridamole (3.1 +/- 1.2, p < 0.01 vs. papaverine). A larger decrease in coronary resistance as measured by the coronary vascular resistance index occurred with papaverine (0.25 +/- 0.06) and adenosine (0.26 +/- 0.09) than with dipyridamole (0.31 +/- 0.10, p < 0.01 vs. papaverine, p < 0.05 vs. adenosine). The maximal coronary blood flow velocity was reached more quickly after the start of adenosine infusion (55 +/- 34 s) than after the start of dipyridamole infusion (287 +/- 101 s, p < 0.0001). The proximal coronary artery diameter was unchanged during dipyridamole or adenosine infusion. Thus, the vasodilator potency of adenosine was greater than that of dipyridamole when changes in coronary resistance were considered, though increases in flow were similar with the two agents. The rapid onset of action of adenosine compared with that of dipyridamole may allow a reduction in the duration of diagnostic studies. The incidence of AV block during adenosine infusion requires evaluation in larger studies.