Potassium-38, a 7.6 minute half-lived radionuclide for assessment of myocardial function

Potassium-38 in isotonic saline solution has been used to study the effect of cardio-active drugs, dipyridamole, propanolol and digoxin on the potassium uptake in the myocardium of dogs. The 38KCl without added carrier was injected intravenously at about 0, 1, 2, and 3 hours after administration of the drug and the dog was scanned with a rectilinear scanner from 10 to 25 minutes after injection. THe counts/sec/mCi corrected for decay were computed for a fixed number of scan elements and compared with controls. Dipyridamole produced a 50 to 80% increase in potassium uptake at 1 hour which returned to normal at 3 hours, Digoxin produced a 10 to 30% increase, and propanolol produced a 25% decrease at 1 to 2 hours. Results are compared with studies of Hamilton using Tl-201. Our results demonstrate that measurements of K-38 uptake can be made at hourly intervals to study the effects of cardio-active drugs