DIAGNOSIS OF CORONARY-ARTERY DISEASE BY CONTROLLED CORONARY VASODILATION WITH ADENOSINE AND TL-201 SCINTIGRAPHY IN PATIENTS UNABLE TO EXERCISE

Pharmacological coronary vasodilation induced by dipyridamole is often used in association with thallium-201 myocardial scintigraphy to evaluate the presence and prognostic significance of coronary artery disease. Because dipyridamole acts by blocking the cellular uptake of adenosine, we investigated the usefulness of direct intravenous administration of adenosine, a physiological substance with an exceedingly short (<2 seconds) plasma half-life, to induce maximal controlled coronary vasodilation in conjunction with 201Tl scintigraphy. We studied 89 patients (44 men and 45 women; mean age, 64±10 years [SD]) who were unable to perform an exercise test and were referred for evaluation of suspected coronary artery disease. The intravenous infusion of adenosine began at an initial rate of 50 μg/kg/min and was increased by stepwise increments every minute to a maximal rate of 140 μg/kg/min. 201Tl was injected intravenously after 1 minute at the highest infusion rate, followed by immediate and delayed (4 hour) tomographic imaging. At the highest infusion rate, adenosine induced a significant (p<0.001) decrease in systolic (8.7±19.3 mm Hg) and diastolic (6.7±9.4 mm Hg) blood pressures as well as a significant (p=0.0001) increase in heart rate (14.5±11.0 beats/min). Side effects occurred in 83% of the patients but resolved spontaneously within 1 or 2 minutes after discontinuing the adenosine infusion. Chest, throat, or jaw pain were the most frequent symptoms and occurred in 57% of the patients. Headache (35%) and flush (29%) were also common. Ischemic electrocardiographic changes occurred in 12% of the patients, and transient first-degree atrioventricular block occurred in 10%. The overall sensitivity and specificity for coronary artery disease detection were 83% and 94%, respectively. Most false-negative studies occurred in patients with one-vessel coronary artery disease. We conclude that maximal controlled pharmacological coronary vasodilation with adenosine, in combination with 201Tl scintigraphy, appears to be a safe and potentially useful test for the diagnosis of coronary artery disease in patients unable to exercise.