title: Repeat dilation of Palmaz stents in pulmonary arteries: study of safety and effectiveness in a growing animal model.
abstract: OBJECTIVE
  This study assessed the technical feasibility and safety of repeat dilation of Palmaz stents in growing pulmonary arteries.
  
  
  METHODS
  Palmaz stents (1.2 cm long) were placed percutaneously into the pulmonary arteries of 20 newborn lambs. After 4 months, pulmonary arteriography was performed. Where vessel growth in excess of stent diameter had created a stenosis (> 15%), stents were dilated again percutaneously. Six months later, pulmonary arteriography was performed, before the animal was killed and histologic examination performed.
  
  
  RESULTS
  Twenty-four pulmonary artery stent placements were attempted; 23 were successful. One stent placement was unsuccessful owing to stent displacement from the balloon. Acute complications included branch pulmonary artery occlusion (n = 3) and stent displacement from the delivery balloon (n = 2). At 4 months, the desired degree of stenosis (> 15%) was achieved in 11 animals. The average stenosis was 35% (standard deviation, 16%; range, 17%-66%). The mean predilation stent diameter was 6 mm +/- 1.1 (range, 4-8 mm), and the final diameter of 8 mm +/- 1.4 (range, 6-10 mm), represented a 35% mean increase (P < .001). Complications included stent (n = 1) and branch vessel (n = 1) thrombosis. At 6-month follow-up, all stents were patent. Areas of previously noted branch thrombosis were fully recanalized in all cases. At histologic inspection, only a thin layer of neointima was found on the stents.
  
  
  CONCLUSIONS
  Repeat dilation of Palmaz stents may be safely performed in growing pulmonary arteries in an animal model. Neointimal hyperplasia is minimal in pulmonary artery stents.
authors.affiliation: Department of Interventional Radiology/Cardiovascular Diagnostic Laboratory, Johns Hopkins Medical Institutions, Baltimore, Md.
authors.forename: S O
authors.initials: SO
authors.lastname: Trerotola
authors.forename: G B
authors.initials: GB
authors.lastname: Lund
authors.forename: J
authors.initials: J
authors.lastname: Newman
authors.forename: J L
authors.initials: JL
authors.lastname: Olson
authors.forename: D M
authors.initials: DM
authors.lastname: Widlus
authors.forename: J H
authors.initials: JH
authors.lastname: Anderson
authors.forename: S E
authors.initials: SE
authors.lastname: Mitchell
authors.forename: F A
authors.initials: FA
authors.lastname: Osterman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002404:Catheterization; D003251:Constriction, Pathologic / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy; D004867:Equipment Design; D005240:Feasibility Studies; D006965:Hyperplasia; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000254:growth & development / Q000473:pathology; D011859:Radiography; D012756:Sheep; D015607:Stents; D017539:Tunica Intima / Q000473:pathology