Autologous vein lined and vein covered stents in swine arteries. An experimental study to assess and compare patency and intimal hyperplastic response.

BACKGROUND

Despite the success of arterial angioplasty as well as arterial stent placement, restenosis remains a significant problem in prolonging blood vessel patency. This animal model was used to test the theory that a stent lined (VLS) or covered (VCS) with autologous vein would be more biologically compatible with the arterial intima. If successful, this technique would prevent angioplasty failure due to intimal hyperplasia (IH) by supplying a healthy endothelial surface and help to eliminate elastic recoil mechanism (ERM) by the use of a stent rendered less thrombogenic in both stenosed and restenosed arteries. There might in addition, be other applications for these modified stents.

METHODS

Nine 50 kg -young pigs had Gianturco-Roubin VLS and VCS mounted on a balloon angioplasty catheter implanted via a transverse arteriotomy. VLS were implanted in 3 left iliac and 6 left carotid arteries and VCS were placed in the matching contralateral arteries. The change from iliac to carotid arteries was due to the initial perception that the iliac artery was the right size for this device. It proved to be too large and the carotid artery, which was initially felt to be too small proved to be the right size. Operative angiography was performed to ensure proper placement. Duplex imaging of the carotid artery placements were performed at 10-14 days. All animals were sacrificed at 30-33 days and specimens examined grossly and microscopically. Three 16.5% of the devices were found to be patent, two VILS and one VCS. The remaining 14 (78%) were occluded by distortion or thrombus or both.

RESULTS

Five devices migrated distally, 2 of which remained patent albeit of smaller diameter. One device migrated to the brain, was not recovered and was presumed occluded. All arteries and veins, with two exceptions, demonstrated varying degrees of IH. We believe failure was due to the inability of the stents to resist ERM in these healthy pig arteries. The IH observed, we believe, is due to the forced dilatation required to seat the devices.

CONCLUSIONS

Based on the observations of the patent devices we suggest that arteries can be relined and supported with modifications of this technique, using a more ERM resistant stent that may be placed without forceful dilatation. This will require further study.