Experimental trial of balloon-expandable, metallic Palmaz stent in the trachea

Objective: To determine the effect of the Palmaz stent, which has been successfully used to relieve airway obstruction in a small group of children, on the normal and operated on animal trachea. Design: In this experimental trial, stents were placed bronchoscopically in the thoracic tracheae of 4 groups of 50 anesthetized cats. The cats in group 1 (adults, n=10) and group 2 (kittens, n=10) had normal tracheae; the cats in group 3 (adults, n=15) underwent horizontal tracheal incision and closure; and the cats in group 4 (adults, n=15) underwent pericardial patch tracheoplasty. In groups 3 and 4, the stents were inserted in 10 cats and 5 cats served as controls. Stents were inflated to a 15-mm diameter in group 1 and an 8-mm diameter in the other groups. Half of the animals with stents were killed 5 weeks after the procedure, and the others, 10 weeks after the procedure. Setting: The Hospital for Sick Children, Toronto, Ontario. Results: In group 1, 1 animal died of tracheal perforation. A mild cough was noted in 15 of the 39 cats with stents. In group 4, 3 cats had difficulty eating and lost weight. The results of esophagoscopy excluded esophageal inflammation or obstruction in these 3 animals. The results of bronchoscopy indicated a nonobstructing rim of granulation tissue at the end of the stent in 15 of 20 cats in groups 1 and 2 and 17 of 20 cats in groups 3 and 4 and at the repair site in all animals with stents from groups 3 and 4. The results of autopsy indicated the cross-sectional area at the site of the stent was greater than normal in group 1 (P<.003) and smaller than the normal trachea at the site of the tracheoplasty in group 4 controls without stents (P<.02); however, the cross-sectional area at the tracheoplasty site with the stent was not smaller (P<.13). The results of histologic examination indicated a mild inflammatory reaction, with granulation tissue in all animals with stents, but in group 1, with overexpanded stents, the reaction was more severe, with epithelial ulceration, fibrosis, and sealed-off perforations in most animals. In group 3, the tracheae with stents had significantly more inflammatory reaction, granulation tissue, and epithelial damage than the controls without stents. Conclusions: The Palmaz stent provokes an inflammatory reaction in the normal trachea and the trachea recently operated on. With the exception of the group 1 animals with overexpanded stents, this reaction is clinically insignificant. The Palmaz stent is able to maintain a normal lumen size after pericardial tracheoplasty in cats.