Improved preparation and application of Tc-99m-heparin for scintigraphic detection of experimental myocardial ischemic injury

Our previous studies demonstrated the localization of technetium-99m-labeled heparin in experimental myocardial infarction. In this report we describe a one-step method for preparation of the labeled agent and further evaluation of the agent in dogs undergoing temporary left anterior descending (LAD) coronary artery ligation for 45 minutes, 3 hours, and 6 hours. Moderate myocardial damage and uptake of technetium-99m-heparin (Tc-99m-heparin) occurred in one of five dogs after 45 minutes of temporary LAD occlusion. Maximum uptake of Tc-99m-heparin occurred after 3 hours of temporary coronary artery occlusion, and exceeded 20 times the activity in the normal myocardium in 4 of 6 dogs with hemorrhagic infarcts. Uptake of Tc-99m-heparin in damaged myocardium was somewhat lower after 60 hours of temporary LAD occlusion in the four dogs studied, but was still in the 15 to 1 range in three with hemorrhagic infarcts. In the animals with prominent histologic damage, there was scintigraphic detection of the damaged myocardium in vivo. These new data confirm that Tc-99m-labeled heparin is suitable for imaging damaged myocardium during early stages of ischemic injury if significant blood flow persists to the damaged myocardial area