Evaluation of ischemic heart disease by serial washout ratio of Tl-201 using dipyridamole with new ring-type single photon emission CT

A new ring-type scinticamera designed for single photon emission CT (SPECT) that allows data collection in a short time was used in dipyridamole-loaded Tl-201 myocardial imaging in ischemic heart disease. The subjects were 22 patients with angiographically proven ischemic heart disease and 6 healthy volunteers. Dipyridamole (0.57 mg/kg) was iv injected over 4 minutes, followed by the iv injection of Tl-201 (3 mCi). Five minutes later, serial eight scans were obtained at 5-minute intervals. Three hours later, 10-minute scanning was performed. Washout ratios were calculated in the septum, anterior, and lateral walls of the myocardium. Using mean-SD of washout ratios at 25 min. in healthy volunteers as the standard, the sensitivity, specificity, and accuracy of washout ratio at 25 min. were 95%, 100%, and 96%, respectively, for evaluating the degree of coronary stenosis. These figures were higher than the corresponding figures of visual diagnostic approach (74% for sensitivity, 100% for specificity, and 79% for accuracy). Side effects of dipyridamole included chest pain (three patients), palpitation (one), slight respiratory distress (one), and transient vertigo (one). Dipyridamole-loaded myocardial ring-type SPECT may be a sensitive, noninvasive approach to the rapid assessment of ischemic heart disease. (N.K.)