Abstract
Simultaneous performance of radionuclide angiography (RNA) and myocardial perfusion imaging during a single exercise test affords the unique opportunity of comprehensive assessment of the physiologic significance of coronary artery stenoses and may increase the sensitivity of radionuclide imaging for overall detection of coronary artery disease. Accordingly, we investigated the feasibility of performing first-pass RNA with iridium 191m, a radionuclide with a half-life of 4.96 seconds, utilizing the multiwire gamma camera, combined with thallium 201 myocardial scintigraphy during a single exercise test. Seventeen patients underwent upright bicycle exercise, and at peak exercise received 30 to 60 mCi of 191mIr and 30 seconds later, received 3 mCi of 201Tl intravenously. RNA images were obtained in the anterior view with the multiwire gamma camera for 30 seconds from the administration of 191mIr and compared with 201T Tl single-photon emission computed tomography (SPECT) images, the acquisition of which commenced five minutes after completion of the exercise. Resting RNA images were obtained immediately before initiation of exercise. High count-rates were attained in the right ventricular phase in all patients and in the left ventricular phase in 14 patients. Six patients had normal exercise and redistribution 201Tl SPECT images. These six patients all had normal wall motion and ejection fraction during exercise. The six patients with coronary artery disease and perfusion defects on 201Tl tomograms had dyssynergy in corresponding myocardial segments and abnormal ejection fraction response to exercise. In two patients the changes observed in the RNA were more striking than the abnormalities on the 201Tl SPECT images. High-quality left ventricular images were obtained and allowed highly reproducible quantification of global and regional ventricular function. Thus, simultaneous assessment of ventricular function, using 191mIr first-pass RNA with the multiwire gamma camera, and perfusion, utilizing 201Tl SPECT, is feasible during a single exercise test. This unique approach may expand the diagnostic usefulness of nuclear cardiac imaging.