Pharmacological coronary vasodilation induced by dipyridamole is often used in association with thallium-201 scintigraphy to evaluate the presence and prognostic significance of coronary artery disease(CAD). Although dipyridamole has traditionally been used for this purpose, it causes frequent side effect, which at times can be life-threatening. Moreover, dipyridamole dose not elicit maximal coronary vasodilation in a substantial number of patients receiving the usual i.v. dose. Adenosine is an endogenously produced compound that has significant effects as a coronary vasodilator and rapid onset action and extremely short half-life(<10 seconds). The safety and diagnostic accuracy of intravenous adenosine Tc-99m MIBI imaging were evaluated in 248 patients who were referred for evaluation of CAD; 51 of the patients underwent coronary angiography and 25 of those exercise Tc-99 MIBI imaging. Adenosine was infused intravenously at a dose of 0.14 mg/kg/body weight per minute for 6 min and MIBI was injected at 3 min.

Adenosine induced a significant decrease in systolic(p<0.05) and diastolic(p<0.001) blood pressures as well as a significant increase in heart rate(p<0.001) and rate-pressure product(p<0.01). The PR interval was slightly prolonged(p-NS). The overall sensitivity, specificity and predictive accuracy for CAD detection was 85%, 82%, and 83%, respectively. The diagnostic accuracy for individual CAD was low in left circumflex CAD. The agreement of segmental perfusion on adenosine and exercise Tc-99 MIBI imaging was 92% (Kappa index-0.83, p<0.001). Side effects occurred in 84% of 248 patients. Flushing (47%), dyspnea(45%), chest pain(28%) and headache(28%) were common. ST depression≥1.0mm occurred in 8% and lst-, 2nd- and 3rd-degree atrioventricular block in 7%, 4%, and 1%, respectively. Side effects were mostly mild and transient except in 3 patients in whom premature termination of adenosine infusion and treatment were necessary. Aminophylline was used in only two patients.

Thus, these facts suggest that pharmacological coronary vasodilation with adenosine in conjuction with Tc-99m MIBI myocardial scintigraphy appears to be a feasible, safe and valuable test for the diagnosis of coronary artery disease, particulary in patients unable to exercise.