Comparison of Two Stent-Grafts with Different Porosity: In Vivo Studies in a Sheep Model

PURPOSE: To compare two stent-grafts with a polyurethane-carbonate (PUC) polymer lining of different pore size and water permeability in the iliac arteries of sheep. MATERIALS AND METHODS: Two stent-grafts with an inner PUC-lining of normal and low water permeability (normal, 1,200 mL/min/cm(2); low, 280 mL/min/cm(2); pressure gradient, 20 mm Hg) were implanted in each of 16 sheep, Hoop strength was two times higher in low-permeable than in normal-permeable stent-grafts. Patency was monitored with use of angiography and intravascular ultrasound (IVUS) after 1, 3, and 6 months. The sheep were killed after 1 or 6 months. Specimens were studied histologically. IVUS and histologic data were analyzed statistically. RESULTS: IVUS measurements showed a wider patent lumen of the low- compared to the normal-permeable prostheses at all time points (P < .03), This is likely due to the greater hoop strength of the low-permeable stent graft. After 1 month, both types of prostheses demonstrated complete transprosthetic tissue penetration and were covered with neointima and endothelium, The neointimal area was greater in low- than in normal-permeable stent-grafts (1 month, P < .005; 6 months, P < .03), CONCLUSIONS: Presumably, the higher permeability of the normal-permeable stent grafts led to the reduced neointimal area by improving transprosthetic capillary ingrowth and endothelialization.