Effect of cardiac drugs on imaging studies with thallous chloride Tl 201.

The effects of commonly used cardiac drugs on cardiac imaging with thallium-201-labeled thallous chloride were studied. This retrospective study included 62 men ranging in age from 37 to 70 years who had cardiac imaging attempted with thallium during an eight-month period. Seven drugs were being used by at least eight patients each--propranolol, nitroglycerin ointment, isosorbide dinitrate, digoxin, hydrochlorothiazide, potassium chloride, and quinidine. Myocardial-to-background (M/Bk) ratios were calculated for each patient. No drug consistently affected the M/Bk ratios. The lowest M/Bk ratio was found in patients receiving digoxin, but there was no significant difference between the M/Bk ratios for patients taking digoxin (1.38 +/- 0.16) and those not taking digoxin (1.45 +/- 0.10) (0.05 less than p less than 0.10, Student's t test). It is concluded that the drugs studied do not affect cardiac imaging with thallous chloride Tl 201.