J Korean Soc Radiol.  2012 Feb;66(2):139-147. 10.3348/jksr.2012.66.2.139.

Vascular Biocompatibility of a Triple Layered Self Expanding Stent-Graft in a Dog Model

• Bae JI
• Won JH
• Jang EH
• Lee SY
• Ko KT
• Jin BH
• Lee JW
• Kim JD

• KMID: 1439405
• DOI: http://doi.org/10.3348/jksr.2012.66.2.139

Abstract

PURPOSE
To evaluate performance and biocompatibility of a newly designed self-expanding stent graft, which consisted of two nitinol stents and an intervening expanded polytetrafluoroethylene membrane in a dog artery model.
MATERIALS AND METHODS
Twelve stent grafts were placed in the aorta of 6 dogs (beagle, mean body weight 11 kg) for 4 weeks (n = 4) and 12 weeks (n = 8). Luminal diameters were measured for each segment (the proximal bare, the middle graft, the distal bare) by angiographies after implantation and follow up periods. Percent luminal stenosis based on angiographies, histomorphometric, histologic, and scanning electron microscopic analyses of each segments were performed.
RESULTS
Blood flow through the stent grafts was good after implantation and during the follow up period, without thrombotic occlusion or stent graft migration. The mean percent luminal stenosis of the proximal bare, the middle grafted and the distal bare segments after 12 weeks were 13.5%, 3.9%, 9.6% retrospectively. The mean neointimal areas of the middle grafted segment were 4.39 mm2 (4 week) and 4.92 mm2 (12 week). Mature endothelialization was evident in over 70% of the area of the stented artery after 4 weeks and in over 90% after 12 weeks.
CONCLUSION
The stent graft was well placed in the attempted area without migration. During the 12-week-follow up period, it showed a good patency without thrombotic occlusion or significant in-stent luminal stenosis. Endothelialization was rapid and nearly complete. Neointima was thin and smooth on the middle graft segment and thicker and irregular on the bare segments.

MeSH Terms

Alloys
Angiography
Animals
Aorta
Arteries
Body Weight
Constriction, Pathologic
Dogs
Electrons
Follow-Up Studies
Membranes
Neointima
Phenobarbital
Polytetrafluoroethylene
Retrospective Studies
Stents
Transplants
Alloys
Phenobarbital
Polytetrafluoroethylene

Figure

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  Fig. 1 The triple layered self expanding stent-graft. It was constructed by two layers of closed cell nitinol stent and intervening expanded polytetrafluosoethylene membrane. The end of outer stent (arrow) become the bare ends of the stent-graft.

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  Fig. 2 An angiographic study of the stent-grafted artery. A. Post-implantation angiogram. A 12 mm-diameter 40 mm-long stent graft (arrows) was placed in the upper abdominal aorta. B. Pre-explantation angiogram after 12 weeks shows widely patent lumen of the stent-grafted aorta. Luminal stenosis is most prominent in the proximal bare segment (arrow).

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  Fig. 3 Macroscopic findings of the stent grafted artery explanted after 12 weeks. A. The inner lumen of the middle of the stent grafted artery is covered with a smooth thin membrane. B. The proximal bare end, covered with the uneven thin membrane (arrow), is slightly protruding into the lumen.

• 

  Fig. 4 Microscopic findings of the stent-grafted artery explanted after 12 weeks (H&E stain, × 10). A. The middle of the specimen. The graft membrane (white arrow) is seen as a gray winding layer. The luminal side of the graft membrane is the neointima composed of smooth muscle cell layer (black arrow) and a single layer of endothelium (arrowheads). B. Neointima (arrows) covering the stent strut (seen as a hollow) is protruding into the lumen at the proximal bare end of the specimen.

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  Fig. 5 Scanning electron microscopic findings of lumen of the stent-grafted artery explanated after 4 weeks. A. The upper row is composed image of × 150 magnified photo of each segment (proximal bare, proximal graft, middle graft 1, middle graft 2, distal graft, and the distal bare segment from the left). Matured endothelial cells covered all area of the bare segments and about 70% area of the grafted segment. Not-matured Endothelialization was noted in the proximal and middle grafted segment. B. The lower row is composed image of × 500 magnified photo. Matured endothelial cells covered all area of the bare segments and about 70% area of the grafted segment. Spindle shaped mature endothelium is evident.

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