Differentiation of transiently ischemic from infarcted myocardium by serial imaging after a single dose of thallium-201.

Abstract

Myocardial 201Tl uptake and regional blood flow by the microsphere technique were determined in anesthetized dogs undergoing either 20 min of coronary occlusion and 100 min of reperfusion (N = 10) or 120 min of occlusion (N = 4). In both groups, 201Tl was injected intravenously after 10 min of occlusion. In transiently occluded dogs, regional flow at the time of 201Tl administration was reduced to 8 +/- 3% of normal flow in endocardial layers of the central ischemic zone. After 100 min of reperfusion, flow values were not significantly different from normal. 201Tl activity after reperfusion rose to 56 +/- 5% of normal, demonstrating that redistribution of the radionuclide occurred during the reflow period. In animals with persistent occlusion, there was a significant relationship between 201Tl uptake and flow (r = 0.95) and no evidence of redistribution of 201Tl during the two hour occlusion period. In another five dogs receiving 201Tl, serial gamma camera images obtained during reperfusion showed increasing uptake of the tracer in apical defects which returned to normal by 4 hours of reflow. Thirteen patients with stable angina received 2 mCi of 201Tl intravenously at peak exercise, and multiple gamma camera images obtained serially. All demonstrated zones of diminished 201Tl uptake 10 min after exercise. Defects which partially or completely disappeared within 1-6 hours postexercise corresponded to areas supplied by coronary arteries with significant stenoses. Persistent defects were present in regions of old myocardial infarction. Six additional patients with acute myocardial infarction demonstrated 201Tl myocardial defects which showed no significant change over 6 hours. Thus, redistribution of 201Tl into ischemic myocardium was demonstrated during transient coronary occlusion in dogs and after exercise stress in man. Sequential imaging after a single dose of 201Tl at the time of exercise may provide a means for distinguishing between transient perfusion abnormalities or ischemia and myocardial infarction of scar.

Serial thallium-201 myocardial imaging after dipyridamole infusion: diagnostic utility in detecting coronary stenoses and relationship to regional wall motion.

“…In contrast to exercise studies, which typically show a large increase in calculated double product, dipyridamole placed a much milder stress on the heart, which supports previous clinical observations of dipyridamole administration in catheterization studies.22 7 Nevertheless, 20% of the CAD patients had angina. This appeared to be related to the presence of multivessel CAD, as five of the 12 patients (42%) with threevessel disease had angina, compared with only three of 28 patients (1 1%) with one-and two-vessel disease (p < 0.01).…”

Thallium-201 peripheral perfusion scans: feasibility of single-dose, single-day, rest and stress study

“…The use of the redistni bution kinetics of 201T1 for the performance of a singlo-dose rest and stress cardiac study has been studied by several investigators [7,12]. In one of these series, qualitatively, ‘¿ ‘¿ the nest images appeared similar to the 4â€"6 hr postexencise images previously obtained' ‘¿ [7].…”

“…It has been suggested that because of this continuous redistribution, if the tracer is administered during stress and permitted to redistribute itself while the subject is at rest, the delayed distribution will reflect perfusion at rest [7].…”

Nuclear Cardiac Stress Testing in the Era of Molecular Medicine

“…Reversible defects correlate with myocardial ischemia as seen by dynamic ECG changes between resting and stress conditions. Likewise, defects observed in resting conditions can be reassessed with repeated delayed imaging (usually 3-4 h or 24 h later) for changes in signal intensity due to radiotracer redistribution (as described with thallium) (22,23). If the defect size decreases from rest to redistribution thallium SPECT (also termed ''fill-in'' or reversible defect), this signifies hypoperfused but viable myocardium (hibernation), which portends a high likelihood for recovery of function after revascularization (24).…”