In Vivo and Post Mortem Dissolution Rates of Pulmonary Emboli and Venous Thrombi in the Dog

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Abstract
Post mortem and in vivo dissolution rates of freshly induced venous thromboemboli were determined in 87 dogs. In 63, fresh thrombi formed in the inferior vena cava (IVC) were embolized to the lungs. Dissolution rates were determined by comparing the embolic volume recovered at autopsy with the volume of a second (control) thrombus formed in the IVC. Embolic volume recovered at 3 hr post mortem averaged 50.2% of control. In dogs maintained alive, embolic volume fell to 48.4% of control at 3 hr. With concomitant heparinization, only 34% of control embolic volume remained at 3 hr. In 24 dogs, thrombi were formed in the jugular veins. No dissolution of these thrombi occurred up to 6 hr post mortem. When they were exposed to circulating blood in vivo, only 67.2% of control volume was recovered at 3 hr. The rapid reduction of thromboembolic volume observed appears to be due to thrombolysis via the fibrinolytic system. The prompt and substantial post mortem and in vivo reduction of embolic volume should be considered in studies dealing with the cardiopulmonary responses following embolism in experimental animals, and perhaps, in man.