Thallium scintigraphy in human transplants: a way to detect myocardial damage.

An original index has been derived from thallium images to detect histopathologic changes in heart transplant patients. One hundred eighty-four static and end-diastolic images with thallium were recorded 5 minutes after injection in the left anterior oblique projection. Twenty patients and 14 healthy volunteers were studied. The epicardial and endocardial borders were determined, and the difference of these values was considered the myocardial area. The results in heart transplants were compared with the results of endomyocardial biopsies (N = 142). A significant decrease (p less than 0.01) was found in the index of the myocardial area between normal biopsy results and mild and moderate rejection. Differences were not detected between studies performed in several postoperative periods in the absence of rejection. The results in healthy volunteers prove that the index does not change between studies performed at different times in the same subject, although the value obtained from the end-diastolic image was more constant. On the basis of these results, it is possible to suggest that the decrease in the myocardial area during rejection is the result of a fall of thallium uptake by the myocardium. Capillary endothelial hyperplasia, perivascular infiltration, and myocytolysis can justify these changes, although the presence of other histologic findings, such as intramyocardial edema, could influence the value of this index. We conclude that the uptake of thallium decreases during acute rejection episodes; the results obtained from the images, in this work, are an expression of this event.