A method utilizing a general dehydrogenase reaction has been used to demonstrate early gross myocardial infarctions. The procedure takes advantage of substrate and enzyme loss from the damaged myocardium. In the viable muscle, where endogenous substrates, coenzymes, and dehydrogenases are present, reduction of Nitro-BT yields a dark blue formazan. Necrotic muscle fibres remain unstained by this technique.
A survey of 31 human hearts obtained at necropsy disclosed that there is no alteration in the Nitro-BT reaction following acute coronary insufficiency with sudden death or severe congestive heart failure. The earliest myocardial infarct to show loss of dehydrogenase activity was of eight hours' duration. Post-infarction scars and patchy interstitial fibrosis provided very precise information concerning topographic relationships when this method was applied to heart slices.