Thallium-201 myocardial imaging in patients with dilated and ischaemic cardiomyopathy.

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Abstract
Ischemic cardiomyopathy and dilated cardiomyopathy may be clinically indistinguishable and cardiac catheterization is often required to differentiate between them. The Tl-201 scintigraphic appearances both on exercise and after redistribution in 13 patients with ischemic cardiomyopathy and 11 patients with dilated cardiomyopathy are described and the usefulness of this noninvasive technique in distinguishing between the 2 groups is assessed. All patients with ischemic cardiomyopathy and 7 of the 11 patients with dilated cardiomyopathy displayed perfusion defects. Reversible defects were equally common in the 2 groups, occurring in .apprx. 60% of patients. Reverse redistribution defects were confined to the group with ischemic cardiomymopathy and were found in 5 patients, and fixed defects were also much more common in this group, being present in 92% compared with 27% of patients with dilated cardiomyopathy. Fixed defects were much more extensive in the gorup with ischemic cardiomyopathy and involved greater than 40% of the outer perimeter of the left ventricular image in 10 of 12 of these patients compared with only 1 patient in the group with dilated cardiomyopathy. The finding of a reversible defect on Tl imaging is nonspecific as to etiology and does not necessarily imply ischemic heart disease. The presence of either a fixed defect involving more than 40% of the outer left ventricular perimeter or a reverse redistribution defect strongly favors an ischemic rather than a dilated cardiomyopathy.