Effect Of Competitive Flow Of Coronary Artery On Patency Of Grafts: An Canine Model Experiment

Coronary artery bypass grafting (CABG) remains the standard for treatment of intractable angina due to coronary artery occlusive disease. Although rare, occlusion of internal mammary artery conduits significantly limits future revascularization options. Causes of occlusion of the arterial bypass grafts remain controversial. Studies suggest that moderate stenosis in the target vessel is associated with competitive flow, thereby leading to a retrograde flow in the arterial graft, which may lead to early failure . Canine experiments have shown that arterial conduits grafted on fully patent native arteries remained patent. Accordingly ,the purpose of our study was to evaluate the influence of of the competitive on the native vessel on the long-term graft patency.Material and MethodsCanine model20 dogs weighting25~30kg were used in the present study. Animals were anesthesized with intravenous injection of sodium barbiturate. After the animal was intubated, then connected with the ventilator. The right internal jugular vein or right general jugular artery was harvested with no-touch technique, then the grafts were grfted onto right coronary artery stem in an end-to-side manner with continuous 7-0 prolene suture. The grafts flow volume were measured with Transit flow measurementPathologic assessmentAt 3 months after operation, 20 grafts and normal vessels segments were fixed and stained with H-E and elastic fiber stains. 3 cross-sections were made in every graft. The histologic sections were connected with Zeiss computerized interactive image analyzing systen (Knotron IBAS 2.5, 2.0),and the intimal thickness, intimal area, and inimal diameter were measured and caculated.Ultrastructural assessmentAt 3 months after operation, the endothelium morphologic features of graft and normal vessels were studied with scanning electron microscopy.Immunochemical assessmentAt 3 months after operation ,the paired grafts were stained with proliferating cell nuclear antigen(PCNA) stain, the intimal and medial PCNA Index(PCNAI) were caculated in Knotron System showing SMC proliferating activity.Ststistical analysisAll dada were expressed as the mean±sd and evaluated with t test or compared by one-way analysis of variance. P value less than 0.05 was considered statistically significant. ResultsVein grafts of two groups showed severe intimal hyperplasia as compared with normal vein. But intimal hyperplasia in control group was more severe than experiment group. Sectional area of experiment group were smaller than that of control group.At 3 months the intimal and medial PCNAI were higher in control group than experiment group.ConclusionWe established successfully canine coronary artery competitive flow model, using this model ,we prove coronary artery competitive flow can be an important factor in long-term graft patency.