Intraoperative delineation of ischemic and scarred myocardium by localized detection of potassium-42 in dogs.

The range of emission from 42-K was shown, in a model experiment, to be suited to scanning with a detector positioned on the surface of the heart after intravenous injection of the isotope. This finding was verified by comparing surface counts with the activity of transmural samples of underlying tissue. Two groups of dogs were studied. In Group A, dogs with left ventricular scars produced by the agar injection technique were given 42-K 24 hours before study. In Group B, normal dogs were given 42-K immediately after ligation of a coronary artery branch. In Group A, localized counting clearly delineated scar from surrounding normal myocardium, and the values were 39 per cent of normal. When more 42-K was given, low flow in scar was indicated by markedly reduced uptake. In Group B, counts over the acutely ischemic area were as low as 20 per cent of normal. Thus, the possibility of differentiating scarred from normal myocardium was shown. Moreover, the results suggest that ischemic but still viable areas that may be suitable for revascularization can be assessed by application of the method.