The use of preintervention and postintervention thallium imaging for assessing the early and late effects of experimental coronary arterial reperfusion in dogs.

Abstract

To determine if thallium-201 imaging of myocardial perfusion can be used as an early predictor of myocardial salvage after reperfusion, 24 adult dogs were subjected to complete occlusion of the left anterior descending coronary artery with release of the snare 2 hr later. Separate doses of thallium (1 mCi) and microspheres were given 15 min before, 5 min after, and 1 hr after release of the snare. Gamma camera images of the heart were obtained after each injection of thallium. Preinjection images were also acquired before the second and third doses and were subtracted from the postinjection images to eliminate the counts due to residual activity from the prior injections. The chest was then closed and the dog allowed to recover. The chest was reopened 48 hr later, final doses of thallium and microspheres were administered, and the heart was imaged. After the dog was killed, the left ventricle was sliced from apex to base, and any infarct was outlined with triphenyltetrazolium (TTC) staining. The slices were then subdivided into pieces of approximately 1 g each and then well counted for microsphere determination of regional myocardial blood flows. Thallium images were interpreted qualitatively and quantitatively. Fifteen dogs with myocardial infarctions, as assessed by TTC staining, all had thallium image defects during coronary arterial occlusion. Thallium scans obtained immediately after reperfusion demonstrated increased anterior wall thallium activity in nine dogs, normal activity in four dogs, and decreased activity in two dogs. In 14 of the 15 dogs, relative thallium activity correlated with the occlusion/normal zone flow ratios.(ABSTRACT TRUNCATED AT 250 WORDS)