Clinical role of 99mTc-MIBI myocardial scintigraphy in the diagnosis of coronary artery disease (CAD) is now well accepted, however, the role of it the identification of viable myocardium in patients with chronic CAD has not yet been clarified.
To
determine the usefulness of rest-injected 99mTc-MIBI scan as a marker of myocardial viability, the regional uptake of this agent at rest was compared with that of 201Tl on reinjection and 24 hours after reinjection images.
Subject patients were 13 chronic CAD patients who showed irreversible perfusion defect(s) on standard pharmacologic (dipyridamole) stress-redistribution images. Immediately after the redistribution images were obtained, 37 MBq thallium was
injected
at
rest, and images were reacquired at 10 minutes and 24 hours after reinjection. After then 740 MBq 99mTc-MIBI was injected, and 1 hour later rest MIBI myocardial imaging was performed. Five sets of images (stress, redistribution, reinjection,
delayed
images of thallium, and rest image of MIBI) were then analyzed qualitatively and quantitatively. Left ventricle was arbitrarily divided into 9 segments (apex, basal and apical portions of anterior, septal, inferior, and lateral walls).
Seven patients and 30 regions showed a fixed perfusion defect on the stress-redistribution images. Among 30 regions, 15 showed positive uptakes and 6 showed negative uptakes on both 201Tl reinjection/delayed images and 99mTc-MIBI rest images.
Five
regions showed only thallium uptake and were regarded as viable clinically. Of four regions which showed only 99mTc-MIBI uptake, two were regarded as viable, while the other two were regarded as a nonviable scar tissue clinically.
IN conclusion, 20Tl reinjection technique was more reliable in the identification of viable myocardium. However, the role of 99mTc-MIBI in identification of viable myocardium was still remained to be clarified because 2 of 9 regions showed only
99mTc-MIBI uptake and were regarded as viable tissues.
|