| Background: Autologous veins are the standard and the most convenience conduits used for the treatment of ischemic heart disease or disease of peripheral artery.But series pathological changes take place after veins are implanted into arterial circulation with higher pressure and pulsatile stress.Thrombosis of the vein graft is the key issue within 1 month .Intimal hyperplasia is the major disease process in venous grafts between 1 month and 1 year after implantation. This process, in itself, rarely produces significant stenosis. Nonetheless, intimal hyperplasia represents the foundation for later development of graft atheroma. In support of this proposal, the localized areas of "adaptive" intimal hyperplasia that occur in native human arteries have been defined by the American Heart Association Council on Arteriosclerosis as "atherosclerosis-prone regions." Beyond the first year after surgery, atherosclerosis is the dominant process underlying the attrition of autologous vein grafts and the eventual recurrence of ischemic symptoms. Occasionally, aneurysms and pseudoaneurysms of saphenous vein coronary artery bypass grafts occur,which lead to thrombosis, embolisation, and rupture eventually.So,veins are not the ideal conduits and need to be improved.In 1978,the impact of the external sleeve on vein wall thickening was realized by Karayannacos and colleagues.Subsequent researchs confirmed the effect of external stent.But the external stent was not used clinically in most cases because of many reasons.Here ,we established canine model of femoral vein-femoral artery interposition grafting on both sides.Each side stented with different caliber external stent.The aim of this study was to investigate the relation between stent caliber and the observed histological changes in vein grafts and to search the ideal caliber of the external stent .The behavior and laws of vein remodeling were what we search for ,too.Methods and Results:Ten canine were divided into two groups,five per group.One was used to test 6mm versus 4mm in diameter(nonrestrictive v.s restrictive),the other used to test 8mm versus 4mm(loose fitting v.s restrictive).Femoral veins and femoral arteries of both sides were dissected using "no touch"technique, ligated all side branches.The veins were removed,reversed and anastomosed end-to-end to femoral arteries using 7-0 Prolene suture.The vein graft was passed through porous PTFE external before completion of the distal anastomosis.Four weeks after grafting,the vein grafts were removed and stained with H.E stain,â…§ R:Ag stain and PCNA stain,then measured.P/VB stain was used to display the distribution of elastic fiber and collagen fiber. Results: 1)In 8mm v.s 4mm,the area and thickeness of total wall cross-section,intimal,medial and adventitia were similar,The lose rate of lumen and percentage of PCNA-positive cells were similar,too. 2) There were no difference between 8mm and 4mm stented grafts in all,too. 3)The approximate of vein grafts had bigger area of total wall cross-section,medial and adventitia (P<0.05) and thicker intimal and medial (P<0.05) than the middle,others were similar.In all the cases the endothelium were intact comfirmed by â…§ R:Ag stain. Conclusions:The small caliber stent has the similar effect as the bigger one when they were used to improve the remodeling of vein grafts.It is unnecessary to select the precise caliber of the external stent. The hyperplasia of vein grafts are asymmetrical ,especially that of intimal and medial.The hyperplasia of the approximate is more severe than the middle,the influence of stoma may be the reason.The mechamism of asymmetrical hyperplasia of the same cross section are not sure and need more research.The endothelial cell injury plays a significant role.The artery circulation influence the intimal hyperplasia little.This study research the relationship between the caliber and the effect through placing different caliber external stent on vein grafts and comparing the the effect on improving vein grafts'remodeling.It comfirmed the as...
|
PDF Full Text Request