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.

The diagnostic reliability and specificity of pulmonary angiography and perfusion photoscanning were examined by applying both technics in two series of dogs: one subjected to multiple small pulmonary emboli; the other, to massive embolization. Interpretations of the angiograms and photoscans by two observers were correlated with each other and autopsy data. Analysis disclosed a high degree of agreement between the two technics. Application of both technics, however, led to a greater incidence and accuracy of embolic detection than either method provided alone. Both technics were subject to interpretive errors leading to false positive and false negative diagnoses. The factors promoting such errors are discussed. It is concluded that the two technics are complementary, not competitive, and that each is least reliable in detecting emboli at the extremes of size.

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