Thoracoscintigraphy in the differential diagnosis of cardiomegaly.

"Thoracoscintigraphy" is a radioisotopic scanning technique for demonstrating the nature of an enlarged cardiac shadow found on chest X-ray. The technique consists of superimposing scintiscans of the cardiac blood pool, the liver and the lungs and comparing the outline of the cardiac blood pool image with the cardiac shadow seen on X-ray. With this procedure the correct diagnosis of pericardial effusion was made in 11 of 15 patients and of pure cardiac dilatation and/or myocardial hypertrophy in three patients. In one of the patients the thoracoscintigraphic diagnosis was equivocal. Thoracoscintigraphy clearly demarcates the cardiac shadow from the surrounding organs, delineates the intracardiac blood pool within the cardiac shadow and indicates the best approach for pericardiocentesis. The procedure is harmless and noninvasive, and the radiation exposure is low and safe.