Abstract
Areas of the heart which are supposedly absent of myocardial viability due to persistent thallium defect in exercise thallium myocardial scintigraphy some-times recover ventricular wall motion through coronary revascularization. To avoid such underestimation of myocardial viability, a "re-injection method" was developed. At the peak of supine ergometer exercise in 51 patients with coronary artery disease, 111 MBq thallium was injected. Conventional exercise and 3 h-delay images were then obtained using single photon emission computed tomography. Subsequently, 55 MBq thallium was injected and a re-injection image was obtained 1 h later. Each image was divided into 12 segments and compared by left ventriculography and coronary angiography. Redistribution was found in 36 patients (71%) on the delayed images and in 44 patients (86%) on either the delayed or the re-injection images (p<0.05). There were 127 re-distribution segments (38%) on the delayed images and 163 (49%) on the re-injection images out of 336 defects on the exercise images (p<0.001). In normokinetic segments with significant coronary stenosis and in hypokinetic segments, redistribution was found in 42% and 45% of the defects, respectively, on the delayed images, and in 65% and 62% of the defects, respectively, on the re-injection images (p<0.01). However, no significant differences were observed between the delayed and either the delayed or re-injection images in the akinetic segments. These results suggest that the re-injection method is useful for avoiding underestimation of myocardial viability.
