Cardioversion and "false positive" technetium-99m stannous pyrophosphate myocardial scintigrams.

The present studies performed in experimental animals demonstrate that electrical direct current cardioversion can produce skeletal muscle damage and increased technetium-99m stannous pyrophosphate (99mTc-PYP) uptake; in experimental animals the electrically damaged skeletal muscle shows necrosis with extensive calcium deposition. In addition, the frequent administration of high energy cardioversion produces myocardial necrosis with calcium deposition, increased 99mTc-PYP myocardial uptake and a positive 99mTc-PYP myocardial scintigram. The data indicate that, if diagnostic 99mTc-PYP myocardial scintigraphy is contemplated after cardioversion, paddle placement should be slightly removed from the anteroposterior projection of the heart on the external chest wall to avoid possible subsequent confusion between increased myocardial and skeletal muscle uptake of 99mTc-PYP. If multiple high energy cardioversion episodes are necessary, myocardial necrosis resulting from electrical injury may occur and be responisble for increased myocardial uptake of 99mTc-PYP with a resultant positive 99mTc-PYP myocardial scintigram.