Establishment Of Off-Pump Coronary Artery Bypass Grafting In Experimental Miniature Pig Model

Objective In Coronary Artery Bypass Grafting(CABG),the autogenous Great Saphenous Vein(GSV)graft remains the most common substitutes.However,vein grafts are subject to early closure(due to thrombus formation)or longer-term occlusion(as a consequence of neointimal formation with or without thrombotic events(vein graft disease).So far,the problem of transplantation vein restenosis has not been solved through a perfect method in clinical.Animal models are a crucial means of testing potential therapeutic and surgical interventions to prevent graft stenosis and occlusion.In our experimental group,the miniature Bama pigs' autologous saphenous vein was used to establish coronary artery bypass graft model effectively,and the surgical procedure is same as the OPCABG in clinical,the environment of vein graft is same as the coronary artery.The research was conducted to investigate the feasibility,repeatability and appropriateness of coronary artery bypass grafting in the miniature pig model utilizing autologous saphenous veins.Methods12 Guangxi Bama miniature pigs(25-30 kg)were selected and the operation began with unilateral lateral autologous saphenous vein harvest for a length of 10-15 cm,1-2cm great saphenous vein from the sample were intercepted and fixed with 10 % neutral formaldehyde,the later GSV were intercepted for observation of intimal hyperplasia and medial thickening after operation.Then reversed saphenous vein underwent proximal anastomosis to the ascending aorta or left subclavian artery followed by distal to anterior descending branch with a continuous suture and ligate the anterior descending coronary artery.Date of intraoperative hemodynamics(four time points was selected,T1: the time after anesthesia,T2: the time of anastomosis with large artery,T3: the time of anastomosis with coronary,T4: the time of before close the chest)and internal environment(two time points was selected,T1: the time after anesthesia,T5:the time of before remove tracheal intubation)were recorded.After the operation,the pigs were treated with intravenous infusion,anti-infective therapy,anticoagulant therapy,feed routinely,and survival for 4 weeks then vein grafts were harvested again from the original incision into chest.The pigs were euthanized and grafts were removed for observation of intimal hyperplasia and medial thickening four weeks later.Results11 of 12 swine operated on survived and all grafts remained patent.First,Introperative hemodynamics satiability and internal environment homeostasis were achieved.Compared T1 with T4: SBP(122.55±9.69 VS 119.36±9.30),DBP(62.8±11.02 VS62.00±7.73),(HR 106.6±14.33 VS 107.55±10.70),(SPO2 98.91±1.22 VS 99.36±0.81)(all P>0.05),compared T1 with T5: there was no significant difference between the indexes before and after process(PH value,Pa O2,Pa CO2,HCO3?,Na+,K+),a significant difference in Serum lactate level was found between before and after process(Lac 0.66±0.16 VS 1.59±0.33,P<0.001).A difference in plasma hemoglobin content was found between before and after process(Hb 110.18±8.73 VS 96.18±7.88,P< 0.05).The significant intimal and medial hyperplasia were observed after the procedure(Intima:199.24±14.07 VS 129.59±10.59,p<0.05)and(medial:211.30±10.47 VS 136.71±9.51,p < 0.05).Pathological section demonstrated a significant development of intimal hyperplasia and medial thickening.Conclusion This study demonstrates the repeatability and appropriateness of establishment of off-pump coronary artery bypass grafting in a swine model for vein graft intimal hyperplasia and medial thickening.These data support progression toward further study of prophylactic therapy to improve vein graft patency.