Noninvasive Assessment of Coronary Stenoses by Myocardial Imaging During Pharmacologic Coronary Vasodilatation. Ill. Clinical Trial PETER C. ALBRO, MD K. LANCE GOULD, MD, FACC R. JEFFREY WESTCOTT, MD GLEN W. HAMILTON, MD JAMES L. RITCHIE, MD DAVID L. WILLIAMS, PhD Seattle, Washington From the Seattle Veterans Administration Hospital and Department of Medicine, University of Washington, Seattle, Washington. This study was supported by Veterans Administration General Medical Research, Seattle, Washington, by Grant-in-Aid 63-2749 and Research Training Fellowships (Drs. Westcott and Albro,) from the Washington State Heart Association, Seattle, Washington and by Grants HL 18492-01, -02 and -03 from the National Institutes of Health, Be- thesda, Maryland. Manuscript received March 2 1, 1978; revised manuscript received June 20. 1978, accepted July 5, 1978. Address for reprints: K. Lance Gould, MD, Seattle Veterans Administration Hospital, 4435 Beacon Avenue South, Seattle, Washington 98108. Thallium-201 myocardial imaging was performed at rest, after maximal treadmill exercise and during coronary vasodilatation induced by the in- travenous administration of dipyridamole in 62 patients undergoing cor- onary angiography. Myocardial images after dipyridamole infusion were compared with rest and exercise thallium-201 images to determine the utility of pharmacologic stress for detecting coronary artery disease. Dipyridamole, 0.142 mg/min, was infused for 4 minutes with electrocar- diographic and blood pressure monitoring, and thallium-201 was injected intravenously 4 minutes after infusion. MyocardiaVbackground count ratios of 2.3 f zyxwvutsrqponmlkjihgfedcbaZYXW 0.5 (mean f 1 standard deviation) after the administration of dipyridamole were higher than similar ratios for exercise images (2.1 f 0.5; P <O.OOl). The sensitivity of thal- lium-201 imaging for detecting significant coronary artery disease was equal for dipyridamole and exercise stress. In 51 patients with a 50 percent or greater stenosis of one or more coronary arteries, image defects were identified in 34 of 51 (67 percent) exercise and dipyridamole images. Twenty of 51 patients (39 percent) had abnormal rest images; in 17 of 20 patients, new or increased image defects were present after exercise and the infusion of dipyridamole. One of 11 patients (9 percent) with no stenosis of 50 percent or greater had a defect on exercise and dipyrida- mole images. Six of seven patients with new or enlarged image defects after the intravenous administration of dipyridamole also had new or en- larged defects after the oral administration of dipyridamole. After the infusion of dipyridamole, the heart rate increased from 64 f 10 beats/min supine to 88 f 13 beats/min standing (P <O.OOl), and blood pressure decreased from 129 f 16/80 f 9 to 120 f 17/75 f 9 mm Hg (P <O.OOl). Angina and S-T depression occurred more frequently with exercise than with dipyridamole. S-T depression occurred in only two patients (3 percent) with dipyridamole, suggesting that diagnostic images were oflen obtained without significant ischemia. This study demonstrates that pharmacologic coronary vasodilatation is as effective as maximal treadmill exercise in creating myocardial perfusion abnormalities de- tectable with thallium-201 imaging in man. Previous studies have demonstrated the feasibility of identifying coro- nary arterial stenosis with thallium myocardial imaging during phar- macologic coronary vasodilatation in animals1s2 and man.3 This report compares the clinical diagnostic sensitivity and specificity of thallium myocardial imaging after coronary vasodilatation induced by intravenous dipyridamole with those of thallium imaging after treadmill exercise stress. November 1978 The American Journal of CARDIOLOGY Volume 42 751