Pulmonary thromboendarterectomy for chronic thromboembolic obstruction of the pulmonary artery in piglets.

Objective: The 2 main causes of death after thromboendarterectomy for chronic pulmonary thromboembolism are incomplete repermeabilization responsible for persistent pulmonary hypertension and acute high-permeability pulmonary edema. We wish to establish an experimental model of chronic pulmonary thromboembolism to replicate the conditions encountered during and after pulmonary thromboendarterectomy.

Methods: Multiple-curled coils and tissue adhesive were embolized in 6 piglets to induce complete obstruction of the left pulmonary artery, documented by angiography. After 5 weeks, the main pulmonary artery was repermeabilized by thromboendarterectomy during circulatory arrest. The left lung was reperfused ex vivo with autologous blood at constant flow, and patency of the pulmonary artery was evaluated on a barium angiogram. The endarterectomy-reperfusion procedure was also done in 6 nonembolized piglets that served as the controls. The severity of lung injury induced by 60 minutes of reperfusion was assessed on the basis of measurements of the lung filtration coefficient and of lung myeloperoxidase activity.

Results: Marked hypertrophy of the bronchial circulation was seen in the chronic pulmonary thromboembolism group. Thromboendarterectomy removed the organized obstructing thrombus that was incorporated into the arterial wall and restored patency of the pulmonary artery. Acute lung inflammation and high-permeability edema occurred after reperfusion, as indicated by a 1.5-fold increases in both lung filtration coefficient and lung myeloperoxidase values in the chronic pulmonary thromboembolism group; these 2 variables being correlated.

Conclusions: Our model replicated the perioperative conditions of pulmonary thromboendarterectomy, suggesting that it may prove useful for improving the repermeabilization technique and for investigating the mechanisms and prevention of reperfusion injury.