To compare the hemodynamic responses and the adverse effects associated with two coronary vasodilators used for pharmacologic stress testing. We retrospectively studied the results of adenosine and dipyridamole perfusion imaging in a large group of patients who underwent pharmacologic stress radionuclide perfusion imaging. One thousand patients given dipyridamole between April 1989 and April 1991 (before adenosine became available) were compared with 1,000 patients given adenosine between April 1991 and October 1992. A standard protocol was used to infuse the drugs before myocardial perfusion imaging with 201TI or 99mTc sestamibi. Peak heart rate was higher (85 versus 83 beats/min; P = 0.02) and systolic blood pressure was lower (129 versus 133 mm Hg; P<0.000l) with adenosine than with dipyridamole. More patients had a decrease in systolic blood pressure of 30 mm Hg or more with adenosine than with dipyridamole (P = 0.002). Horizontal or downsloping ST -segment depression of 1 mm or more occurred in 9 % of patients who received adenosine and in 8 % of those who received dipyridamole. Adverse effects occurred in 78% of the adenosine study group and in 50% of the dipyridamole group (P<0.0001). Chest pain was the most common symptom with both drugs. Atrioventricular block occurred in 76 patients who received adenosine but in none who received dipyridamole. Because of adverse effects, 28 % of patients who received dipyridamole required extra monitoring time (mean, 6 ± 5 minutes beyond the standard protocol). Aminophylline was administered to 163 and 6 patients, respectively, in the dipyridamole and adenosine study groups. Adenosine causes slightly greater systemic vasodilation than does dipyridamole. Adverse effects occur less often with dipyridamole but, in comparison with adenosine, are more difficult to manage and necessitate more monitoring time as well as fairly frequent intravenous use of aminophylline for reversal.
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