REPEAT DILATION OF PALMAZ STENTS IN PULMONARY-ARTERIES - STUDY OF SAFETY AND EFFECTIVENESS IN A GROWING ANIMAL-MODEL

PURPOSE: This study assessed the technical feasibility and safety of r epeat dilation of Palmaz stents in growing pulmonary arteries. MATERIA LS AND METHODS: Palmaz stents (1.2 cm long) were placed percutaneously into the pulmonary arteries of 20 newborn lambs. After 4 months, pulm onary arteriography was performed. Where vessel growth in excess of st ent diameter had created a stenosis (> 15%), stents were dilated again percutaneously. Six months later, pulmonary arteriography was perform ed, 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 st ent displacement from the balloon. Acute complications included branch pulmonary artery occlusion (n = 3) and stent displacement from the de livery balloon (n = 2). At 4 months, the desired degree of stenosis (> 15%) was achieved in 11 animals. The average stenosis was 35% (standa rd deviation, 16%; range, 17%-6%). 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). Comp lications included stent (n = 1) and branch vessel (n = 1) thrombosis. At 6-month follow-up, all stents were patent. Areas of previously not ed branch thrombosis were fully recanalized in all cases. At histologi c inspection, only a thin layer of neointima was found on the stents. CONCLUSION: Repeat dilation of Palmaz stents may be safely performed i n growing pulmonary arteries in an animal model. Neointimal hyperplasi a is minimal in pulmonary artery stents.