Quantitative thallium-201 redistribution with a fixed coronary stenosis in dogs.

Abstract

The redistribution of thallium-201 (201Tl) after coronary vasodilation was studied in 14 dogs with a proximal stenosis of the left circumflex coronary artery that did not reduce basal flow but attenuated reactive hypermia. During an 8-10-minute i.v. infusion of adenosine, radioactive microspheres and 201Tl were injected into the left atrium. Sequential cardiac scintiscans and microsphere injections permitted subsequent determination of coronary blood flow during the redistribution of 201Tl. After 15-220 minutes of observation, the dogs were killed and the hearts removed for the measurement of the activity of 201Tl and the radioactive microspheres in the normal (left anterior descending coronary artery [LAD]) and flow-restricted (left circumflex coronary artery [LCX]) regions. The ratios of the activity in LAD/LCX for microspheres (TRmic) and for 201Tl (RT1) were compared with the activity ratio determined from the scintiscan (Rscan). Rmic for the microsphere simultaneously injected with 201Tl can be compared with the initial Rscan, which showed a significant hourly decrease from an initial value of 1.26 +/- 0.12 to a mean final value of 1.02 +/- 0.09 by 3-4 hours. The final Rscan (mean 1.07 +/- 0.10) in each experiment also correlated significantly (r = 0.854) with the final true myocardial RT1 (mean 1.26 +/- 0.25). Rscan underestimated Rmic (average 2.25 +/- 0.48) when both 201Tl and microspheres were simultaneously injected; Rscan also underestimated RT1, but the directional changes were similar. A further analysis of the Rmic, Rscan and RT1 in two groups of dogs with either relatively high or low coronary flow during adenosine infusion suggests that the net loss of cellular 201Tl from the normal scintigraphic area is the mechanism underlying the resolution of these initial defects.

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

“…42 The results of the present study suggest that the factors affecting whether an initial defect fills in after dipyridamole are similar to those affecting exercise studies. The excellent correlation between regional dipyridamole thallium-201 redistribution results and regional wall motion is consistent with observations in exercise myocardial perfusion studies,>'°22 as is the significant superiority of the scan data to the ECG data in predicting akinesis or dyskinesis.9 '°O ur qualitative interpretation of serial thallium-201 images after dipyridamole yielded a sensitivity of 84% and a specificity of 82% for detecting asynergy.…”

Scintigraphic evaluation of myocardial uptake of thallium 201 and technetium 99m pyrophosphate utilizing a rat model of chronic doxorubicin cardiotoxicity

“…Considering the similarity between T1 and K, it is likely that the fourth mechanism may play a role in the slow wash-out of T1 from the heart. Although the mechanism of redistribution is not well understood at present, passive diffusion and/or disturbances of T1 output from damaged myocardial cells may be major contributing factors to the redistribution (Leppo et al 1981;Bergmann et al 1982;Nishiyama et al 1982). If so, our data suggest some disturbances.in T1 output even in the early stages of DXR-induced ca rdiomyopathy.…”

Diagnosis of coronary artery disease by controlled coronary vasodilation with adenosine and thallium-201 scintigraphy in patients unable to exercise.

“…24 In this study, we sought to assess the feasibility, safety, and diagnostic accuracy of controlled pharmacological coronary vasodilation with adenosine in combination with 20MT1 scintigraphy for diagnosing coronary artery disease in patients unable to perform an exercise test.…”