STRESS-TESTING WITH CLOSED-LOOP ARBUTAMINE AS AN ALTERNATIVE TO EXERCISE

Objectives. This study compared exercise and pharmacologic stress test ing using arbutamine delivered by a closed-loop device for the detecti on of coronary artery disease. Background. Arbutamine, an agent design ed to simulate exercise, has been developed in conjunction with a clos ed-loop delivery device that modulates the rate of administration on t he basis of physiologic feedback. Methods. Two hundred ten patients (1 80 men, 30 women) with symptoms and angiographic evidence of coronary artery disease were studied. Ischemia was categorized in three ways: 1 ) the presence of angina; 2) the occurrence of greater than or equal t o 0.1-mV horizontal or downsloping ST segment depression or elevation at 60 ms after the J point; or 3) the presence of either condition 1 o r 2.Results. In the 210 patients, the mean increase in heart rate and systolic blood pressure evoked by arbutamine and exercise was 51 and 5 3 beats/min (p = NS) and 36 and 44 mm Hg (p < 0.0001), respectively. A rbutamine detected ischemia more often than exercise with each of the three ischemic end points. Sensitivity for detecting ischemia by eithe r angina or ST segment change was 84% (95% confidence interval [CI] 79 % to 89%) for arbutamine and 75% (95% CI 69% to 81%) for exercise test ing (p = 0.014). For angina alone, sensitivity was 73% (95% CI 67% to 79%) for arbutamine and 64% (95% CI 57% to 71%) for exercise (p = 0.02 6). For ST segment change alone, sensitivity was 47% (95% CI 40% to 54 %) far arbutamine and 44% (95% CI 37% to 51%) for exercise (p = 0.426) . Cardiac events occurred in five patients (1.8%) within 24 h of the a rbutamine test. Conclusions. In detecting documented coronary artery d isease, the sensitivity of arbutamine testing was equal to that of exe rcise for the electrocardiographic end point of ST segment change alon e. Arbutamine testing was significantly superior to exercise testing f or either ST change or angina or for angina alone.