Safety of pharmacological (intravenous dipyridamole) stress for Thallium-201 perfusion imaging in patients with coronary artery disease unable to exercise.

Exercise Thallium-201 myocardial perfusion imaging is a sensitive technique for detection of CAD. However, in patients unable to perform exercise pharmacological stress with intravenous dipyridamole can be used to dilate coronaries. Out of 125 patients (21 men and 104 women; mean age 52.03 years) evaluated, 110 were considered to be unable to perform adequate stress by their physician while remaining 15 had LBBB. One hundred and seven patients had chest pain with or without a remote MI while 18 individuals were clinically asymptomatic but had ECG abnormalities. Intravenous dipyridamole was administered at a rate of 0.142 mg/kg/min for 4 min. After 3 min an i.v. bolus of T1-201 was given. Diffuse or occipital headache of mild to moderate intensity occurred in 50 (40%) cases; 39 patients experienced chest pain and had either a positive thallium scan (26 cases) suggestive of CAD or a normal thallium study (15 cases). Complete relief from dipyridamole induced symptoms was brought by i.v. aminophylline and sublingual nitrate in 51 of 54 cases (94%) and 11 of 18 (61%) respectively. We, therefore, conclude: 1) i.v. dipyridamole-thallium scintigraphy offers a safe, effective and reliable method for evaluating CAD in those who are unable to perform adequate exercise and 2) parenteral aminophylline is very effective antidote to dipyridamole.