Noninvasive assessment of coronary stenoses by myocardial imaging during pharmacologic coronary vasodilatation. III. Clinical trial

Thallium-201 myocardial imaging was performed at rest, after maximal treadmill exercise and during coronary vasodilatation induced by the intravenous administration of dipyridamole in 62 patients undergoing coronary 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 electrocardiographic and blood pressure monitoring, and thallium-201 was injected intravenously 4 minutes after infusion.Myocardial/background count ratios of 2.3 ± 0.5 (mean ± 1 standard deviation) after the administration of dipyridamole were higher than similar ratios for exercise images (2.1 ± 0.5; P < 0.001). The sensitivity of thallium-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 dipyridamole images. Six of seven patients with new or enlarged image defects after the intravenous administration of dipyridamole also had new or enlarged defects after the oral administration of dipyridamole.After the infusion of dipyridamole, the heart rate increased from 64 ±10 beats/min supine to 88 ± 13 beats/min standing (P < 0.001), and blood pressure decreased from $\text{129 ±}\text{16}\text{80}\text{± 9}\text{to}\text{120 ±}\text{17}\text{75}\text{± 9}\text{mm Hg}\text{(P < 0.001)}$. 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 often obtained without significant ischemia. This study demonstrates that pharmacologic coronary vasodilatation is as effective as maximal treadmill exercise in creating myocardial perfusion abnormalities detectable with thallium-201 imaging in man.