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 c hildren, on the normal and operated on animal trachea. Design: In this experimental trial, stents were placed bronchoscopically in the thora cic 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 ca ts in group 3 (adults, n=15) underwent horizontal tracheal incision an d closure; and the cats in group 4 (adults, n=15) underwent pericardia l 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 Si ck Children, Toronto, Ontario. Results: In group 1, 1 animal died of t racheal 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 obstructi on in these 3 animals. The results of bronchoscopy indicated a nonobst ructing 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 result s of autopsy indicated the cross-sectional area at the site of the ste nt was greater than normal in group 1 (P<.003) and smaller than the no rmal trachea at the site of the tracheoplasty in group 4 controls with out stents (P<.02); however, the cross-sectional area at the tracheopl asty site with the stent was not smaller (P<.13). The results of histo logic examination indicated a mild inflammatory reaction, with granula tion tissue in all animals with stents, but in group 1, with overexpan ded 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, gr anulation tissue, and epithelial damage than the controls without sten ts. Conclusions: The Palmaz stent provokes an inflammatory reaction in the normal trachea and the trachea recently operated on. With the exc eption of the group 1 animals with overexpanded stents, this reaction is clinically insignificant. The Palmaz stent is able to maintain a no rmal lumen size after pericardial tracheoplasty in cats.