Heterotopic pig model for direct revascularization and venous drainage of tracheal allografts

Abstract

A macrosurgical technique of thyrotracheal harvesting and direct revascularization with and without venous drainage in a heterotopic thyrotracheal and immunosuppressed allograft in the pig model is described. Harvesting included en bloc cervicothoracic exenteration of the aortic arch and its supraortic trunks, anterior vena cava, jugular veins, subclavian vessels, thyroid gland, cervicothoracic trachea, and esophagus. This technique conserves the tracheal arterial supply provided by either the right or left subclavian artery, directly or indirectly via the inferior thyroid artery, and venous return provided by the anterior vena cava, directly or indirectly via the descending cervical vein. In recipients, implantation included (1) arterial end-to-end anastomoses of the proximal and postscalenic stumps of donor's subclavian artery to the proximal and prescalenic stumps of recipient's subclavian artery; (2) end-to-side venous anastomosis of the donor's anterior vena cava to the recipient's brachiocephalic venous trunk; and (3) heterotopic implantation of the proximal and distal orifices of the grafted trachea into the neck. Ten adult Large White pigs underwent direct revascularization of a thyrotracheal allograft with (n = 6, group 1) and without (n = 4, group 2) venous drainage. All grafts of group 2 exhibited a venous infarction, extensive inferior thyroid artery thrombosis, and ischemic and suppurative thyrotracheal necrosis 1 to 2 days after transplantation. In group 1, the length of the grafted trachea and number of rings were 9.75 +/- 1.5 cm and 22.1 +/- 3.3, respectively; ischemic time was 236.3 +/- 338.3 minutes. Group 1 pigs were put to death 4 (n = 4) and 3 (n =2) weeks after transplantation. All tracheal grafts had histologically normal airway epithelium; isolated areas of necrotic ischemia of the chorion and submucosa lasted for the first 7 days after transplantation but disappeared after epithelial regeneration. Premortem angiograms showed that all vascular anastomoses were patent. Grafts were histologically normal at postmortem examinations and all but one had no rejection. This large animal model demonstrates that long tracheal allografts might be transplanted by means of this direct revascularization and venous drainage technique.