[Reaction of the blood vessel wall to microporous endovascular prostheses]

Sealing endovascular prostheses enable transluminal exclusion of aneurysms, fistulas and arterial leakage. This study investigated the tissue response towards a newly developed microporous stent within the unaffected porcine aorta in respect to angiographic and histologic findings.

The device consisted of a self-expandable stent of wire filaments with integrated polyurethane. Under fluoroscopic guidance the stents (diameter 6 and 10 mm) were deployed into the infrarenal aorta of 3 animals. Follow-up was scheduled for 1 month. Radiographs and angiographies were performed before, immediately after stent deployment and before the explantation procedure. The grafts were examined by light microscopy, immunocytochemistry and both scanning and transmission electron microscopy. Quantitative analysis was performed in respect to the tissue layers and the amount of polyurethane and elastin.

Angiographic findings revealed stable stent position and patency without luminal narrowing. The trombus-free luminal stent surface was 67%. The tissue response consisted in total tissue ingrowth through micropores forming an even neointimal lining (273 +/- 225 microns). Restricted to the polyurethane a moderate foreign body reaction of giant cells was observed. The luminal surface showed focal endothelialization (19 +/- 19%). The tunica media was diminished (from 767 +/- 146 microns to 312 +/- 132 microns, p = 0.0001). The amount of elastin of the tunica media underlying the stent did not decrease essentially (from 3.63 +/- 1.25% in normal aorta to 3.74 +/- 2.54%, p = 0.9221). The amount of polyurethane did not change in comparison to pre-implantation (19.4 +/- 0.9% and 18.3 +/- 3.2%, respectively, p = 0.6098).

Reliable stent anchorage, incorporation of the stents in the underlying artery and a thin neointimal lining with focal endothelialization were obtained after the implantation of the covered microporous self-expandable stents in the porcine model.