A porcine model of massive, totally occlusive, pulmonary embolism

Abstract

Background A reliable, animal model of massive, totally occlusive, pulmonary embolism (PE) is lacking. Objectives To design an animal model of totally occlusive PE and to challenge the model by a plasminogen activator. Methods In eight anaesthetized pigs (~ 90 kg) a massive preformed autologous thrombus was injected into the caval vein. One animal was autopsied to assess the extent of injected clot, whereas in the other animals extracorporeal life support (ECLS) was initiated and continued for three hours. These animals received 100 mg rt-PA. Blood gases, coagulation tests, creatine kinase (CK), lactate dehydrogenase (LDH), end-tidal CO2, systemic and pulmonary artery blood pressures and flow were registered. Results All animals went into circulatory arrest within 2 minutes after injection of the thrombus. In the animal where ECLS was not started, autopsy relieved a totally occlusive embolus of the pulmonary artery. The ECLS maintained a systemic blood flow of 6-8 L/min with adequate oxygenation and CO2-removal. However, lactate increased and base-excess became negative. Ddimer increased, fibrinogen decreased, and CK and LDH increased. All seven animals were weaned from ECLS. Despite the rt-PA treatment, the animals had at that time low end tidal CO2/PaCO2 ratio and increased mean pulmonary arterial pressure, suggesting a significant amount of embolic material remaining in the pulmonary artery. Conclusion This model of massive, totally occlusive, pulmonary embolism mimics well fatal PE seen in the clinic, and has the potential for use in testing of new therapeutic interventions.