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PURPOSE: To evaluate, by digital morphometry, the intimal thickening after the placement of two different kinds of stents: polyester covered stainless steel stents (Dacron) and non-covered stents implanted in young pigs' infrarenal aortas. METHODS: The experiment was carried out on two separate groups of pigs. Eight polyester-covered stainless steel stents (Dacron) and eight stainless steel stents (30-mm long, 8-mm diameter) were deployed through extraperitoneal approach in the normal infrarenal aorta of 16 normolipemic pigs. To allow the passage of the delivery system, a small arteriotomy was performed (phase I). After four weeks, the aorta with the stent was removed en bloc. (phase II). The values of the hematimetric and lipid analysis did not show any changes that could influence the study. Tissue samples of the fixing sites (proximal and distal) of the stents were taken. Microscope slices were prepared and submitted to Verhoeff's hematoxilin and eosin techniques and sent to morphometric analysis. RESULTS: The intima immediately proximal to the device was thicker in the group of covered stents with marginal significance (p=0.054). The distal intimal layer (p=0.185), proximal medial layer of the proximal portion (p=0.141) and distal portion (p=0.375) did not present statistical difference between the two groups. CONCLUSIONS: Patency was 100% in both groups of these normolipemic pigs. After four weeks the intimal layer immediately proximal to the covered stents was ticker when compared to uncovered stents, but this had a borderline significance. The intimal layer distal to covered stents and the media proximal or distal to the devices had similar morphometric features when covered and uncovered stents where compared. OBJETIVO: Avaliar através de morfometria digital o espessamento intimal após o implante de dois tipos de stents de aço inoxidável, um recoberto com poliéster (dacron) e outro não recoberto, implantados na aorta infra-renal de suínos jovens. MÉTODOS: O experimento foi realizado em dois grupos (stents não revestidos e revestidos com dacron) e duas fases (I e II). Oito stents recobertos com dacron e oito stents de aço inoxidável (30mm de extensão e 8 mm de diâmetro), não revestidos, foram implantados através de abordagem retroperitoneal na aorta infrarenal normal de 16 suínos normolipêmicos. Para a passagem do sistema de implante, foi necessário uma pequena arteriotomia na aorta distal (fase I). Após quatro semanas, a aorta com os stents foram removidas em monoblocos (fase II). Os valores de hematimetria e do lipidograma foram coletados nas duas fases e não apresentaram alterações que pudessem influenciar o estudo. Amostras de tecido dos sítios de fixação (proximal e distal) dos stents foram retiradas, confeccionadas lâminas, que foram coradas pelas técnicas de hematoxilina e eosina e de Verhoeff e enviadas para análise morfométrica digital. RESULTADOS: A camada íntima proximal ao stent apresentou maior espessamento intimal no grupo de stents recobertos, mas com significância limítrofe(p=0.054). A camada íntima distal(p=0.185), a camada média das regiões proximal(p=0.141) e da porção distal (p=0.375) ao stent não apresentaram diferença entre os grupos. CONCLUSÕES: Os dois tipos de stents apresentaram 100% de perviedade, boa biocompatibilidade e boa incorporação a parede aórtica de suínos normolipêmicos. A camada íntima proximal do grupo de stents revestidos com dacron apresentou maior espessamentodo que os stents não revestidos, mas com significância estatísitica limítrofe

Digital morphometric analysis of the aortic wall in pigs following implantation of dacron-covered stents versus non-covered stents