An experimental model of pulmonary embolism

Abstract

Previous experimental studies have contributed to the diagnosis and management of pulmonary embolism in patients. However, most experimental techniques to produce pulmonary embolism used material with a structure and composition quite unlike the pulmonary emboli which occur in patients. This report describes a method to induce pulmonary embolism by using a subcutaneously implanted prosthetic graft for thrombus formation. Dogs were prepared by anastomosis of the graft from the distally ligated carotid artery to the proximally ligated femoral artery to provide initial blood flow which led to gradual graft occlusion by laminar deposition of fibrin and blood elements. Seven of 10 animals examined developed a large quantity of formed thrombus within the graft 5 days following implantation. A subsequent intravenous administration of a quantity of 0.2 g/kg of animal weight produced a massive pulmonary embolus which caused hemodynamic alterations in all 36 animals studied and proved lethal in four. Pulmonary embolism was induced in 20 dogs and the systemic arterial pressure, pulmonary arterial pressure, pulmonary arterial blood flow, left atrial pressure, static and dynamic lung compliance were observed for a 2-hr period. One group of 10 dogs was subjected to pulmonary embolism using fresh autologous blood clot, and the other group of 10 dogs was subjected to formed thrombus obtained by gradual occlusion of a prosthetic graft anastomosed to the carotid and femoral arteries and placed subcutaneously. Neither group of animals demonstrated significant alterations of systemic blood pressure. However, two animals died and two other animals developed significant hypotension in the group of 10 animals subjected to formed thrombus pulmonary embolism. None of the animals subjected to autologous blood clot developed significant hypotension. The pulmonary artery pressure increased in animals subjected to clot but returned to control values within 60 min. A much larger increase in pulmonary artery pressure was observed following embolism using formed thrombus and the pulmonary artery pressure remained elevated for the duration of study. Pulmonary mean blood flow did not change significantly in dogs subjected to clot but decreased significantly for a 60-min period in dogs subjected to formed thrombus. Left atrial pressure increased and static and dynamic compliance decreased significantly in dogs subjected to formed thrombus embolism, but no significant changes occurred in dogs which received fresh blood clot. This study documented significant differences in hemodynamic and ventilatory alterations induced by material with different mechanical properties. In addition, these observations indicate that the approach to inducing pulmonary embolism using thrombus recovered from a subcutaneous graft represents a useful experimental technique for evaluation of pulmonary embolism.