Influences Of EPTFE Cuff On Accelerated Atherosclerosis Of Implanted Vein In Rabbit

ObjectivesIn order to observe process of accelerated atherosclerosis of vein and prevention effects of ePTFE cuff after bypass surgery, common carotid artery were reconstructed with ipsilateral facial vein in rabbits. The aim of this research is to provide theoretical basis for prevention of acceleration atherosclerosis after bypass surgery.MethodsThirty healthy rabbits(2.0~2.5kg) were randomly divided into experimental and control groups(15 in each group). The implanted veins in experimental group were enclosed by expanded polytetrafluoroethylene(ePTFE) cuff and that of the control group were not enclosed. Common carotid artery was reconstructed with ipsilateral facial vein by microsurgical technique, rabbits were fed with high fat and high cholesterol diet after operation. After 4, 6 and 8 weeks of operation, graft vein was exposed by original incision cutting under general anesthesia with QMB, general morphology of graft vein was first observed, The removed vein was fixed by pressure perfusion with formalin at 100 mmHg for 24 h. After fixation, one was imbedded in paraffin and stained with haematoxylin-eosin and Verhoeff’s elastic fibers for histological analysis, the intimal thicknesses were determined using OLYMPUS IX71 image analysis system; the other was used as frozen section and stained with Oil red "O" for observation of lipid deposition in the wall in different time course.Results1. Patency rate of implanted veinImmediate postoperative patency rate of graft vein was 100% in two groups. In control group, a rabbit had abscess in the surgical incision at 4w postoperatively, a large number of pus in the wound can be squeezed out, then we found the bypass graft disappeared, one implanted veins was obstructed at 6w and 8w of postoperation,respectively, patency rate was 80%. In experimental group, only one graft vein wasobstructed till 8w postoperatively, the remaining 14 implanted veins were all maintained patency in different time course, total patency rate was 93.33%.2. Gross morphological observation at different time coursePatency vessels were well pulsed. In control group, the implanted vein was wrapped by connective tissue with hardening of blood vessel, dilated lumen and uneven thickness. However, in experimental group, the outer wall of ePTFE cuff had a little adhesion with adjacent tissue, and the inner wall of ePTFE cuff almost had no adhesion with implanted veins, the implanted veins were slightly dilated and the thickness was uniform.3. Intimal thickness changes of implanted veinIntimal thickness in control group and experimental group were 119.04±0.42 and89.95±0.08μm at 4w postoperatively. Compared with 4w of postopertion, thickness in control group was extremely thickened at 6, 8w(P<0.01), but thickness in experimental group was extremely thickened at 8 w(P<0.01) after bypass surgery.Compared with the control group, intimal thickening in experimental group was extremely decreased at different time course(P<0.01).4. Effect of ePTFE cuff on histological changes of implanted vein at different time courseResults of HE stain: Intimal hyperplasia degree of vein graft in two groups was different, there was vacuoles in intima. A large number of lymphocytes and a small number of monocytes attached to the blood vessel intima in control group, which indicated inflammatory cells attach to intima following prolong of time course, while there was less inflammatory cells attach to intima in experimental group. Compared with experimental group, control group smooth muscle cells arranged disorder in intimal hyperplasia.Results of verhoeff’s elastic fiber stain: After 4w of operation, black elastic fibers were clearly visible and the continuity was complete in the media of implanted veins in experimental group, elastic fibers were broken, thin and migrated to hyperplasia intima at 6, 8w time course. However, brokening and thinning of elastic fibers occured at 4w postoperatively, and it was more serious following prolong of timecourse in control group. Intimal hyperplasia was composed of dense layers of smooth muscle cells(yellow stained), inflammatory cells(dark blue stained of nucleus),collagen fiber(red stained) and disintegrating migration of elastic fibers(black stained).5. Lipid deposition of the implanted veinFrozen section oil red "O" staining showed that there was no lipid deposition in both groups after 4w of surgery; jacinth lipid was deposited in blood vessel wall and hyperplasia intima at 6, 8 w after bypass surgery, bigger and more intensive lipid droplets was deposited in hyperplasia intima at 8w. However, less lipid droplets was deposited in blood vessel wall at 6, 8 w after bypass surgery, while there was small and sparse lipid droplets deposited at hyperplasia intima in experimental group.ConclusionsCommon carotid artery was successfully reconstructed with ipsilateral facial vein by vascular bypass surgery in rabbit. Intimal hyperplasia was significantly reduced and lipid deposition was significantly decreased when implanted vein was enclosed by ePTFE cuff. It was concluded that ePTFE cuff could retard process of accelerated atherosclerosis.