Experimental Study Of Percutaneous Aspiration Thrombectomy For Acute Mesenteric Arterial Embolism In Different Pathological Stage

Part one:The establishment of the animal model of acute superior mesenteric artery embolizationObjective:To establish the animal model of acute mesenteric artery embolization suit for following interventional embolectomy study,and to evaluate the early diagnostic value of plasma D-lactate and serum LDH for acute intestinal ischemia.Material and Methods:Two dogs randomly selected as contrast group in 6 dogs and the other 4 dogs belonging to the research group.After anesthetized, intestine was exposured after a midline laparotomy.And then,with seldinger technique,An 8Fr and a 5Fr sheath were inserted into femoral artery and femoral vena respectively.Then we suctioned 40ml arterial blood from the 8-F sheath,which were mixed with 2.5ml EACA.The mixture was clotted under room temperature for 30 minutes,and then being immersed in 70℃water for 10 minutes,keeping them in refrigeratory for more than 10 minutes.In research group,an 8-F arterial sheath was inserted into the distal segment of the trunk of the superior mesenteric artery,by which thrombi were injected into the trunk of the superior mesenteric artery form distal to proximal segment to establish the animal model of acute superior mesenteric artery embolization.Repeated selective SMA angiography was performed 2,4,6 and 8 hours after embolization to confirm whether the thrombi was stable and whether there was recanalization automatically in the superior mesenteric arteries.Abnormal bowel biopsies examined by standard HE slide preparations were performed 2,4,6 and 8 hours after embolization respectively.Hematal enzyme in systemic circulation, including plasma D-lactate and serum LDH,were obtained at baseline,2,4,6 and 8 hours after embolization.Instead of injecting thrombi into SMA,selective SMA angiography was performed in contrast group.Bowel biopsies examined by standard HE slide preparation was performed 8 hours after operation.Plasma D-lactate and serum LDH were obtained at pre-operation and 2,4,6,8 hours after operation.Results: The acute superior mesenteric arterial embolism models were successfully established in all research dogs.Intestinal ischemia was found in all of the 4 dogs with good consistency,and the ischemic degree was aggravated over time.Ischemic injuries were limited to the intestinal mucosa 2 hours after embolization and extended into submucosal and muscular layers 4 and 6 hours after embolization respectively. Transmural bowel wall necrosis was developed 8 hours after embolization.Intestinal ischemia injuries resulted in a elevation in plasma D-lactate and serum LDH levels.A significant elevation in plasma D-lactate levels was found at 2 hours after acute mesenteric arterial embolism(P＜0.05),while the serum levels of LDH elevated significantly at 4 hours post embolization(P＜0.05).No gross and microscopic changes of bowel were found in contrast group,and there were no obvious changes of plasma D-lactate and serum LDH levels before and after operation in contrast group either.Conclusion:Animal models with acute superior mesenteric arterial embolism can be established by this interventional technique successfully.Intestinal ischemia injuries resulted in a significant elevation in plasma D-lactate and serum LDH levels. Plasma D-lactate specifically elevated early,and might be a useful early predictor of acute mesenteric ischemia.Part two:Experimental study of percutaneous aspiration thrombectomy for acute mesenteric arterial embolism in different pathological stageObjective:The aim of the study was to evaluate the security and feasibility of percutaneous aspiration thrombectomy for acute mesenteric arterial embolism performed in different pathological stage,and to observe the dynamic changes and its meaning of plasma D-lactate and serum LDH levels before and after thrombectomy.Material and Methods:12 acute superior mesenteric arterial embolism animal models created as study one were randomly divided into 3 groups, in which percutaneous aspiration thrombectomy with 8-F arterial sheath was performed in 2,4 and 6 hours after embolism respectively.Hematal enzyme in systemic circulation,including plasma D-lactate and serum LDH,were obtained at baseline,2,4,6 hours after embolization,and 2,4,6 8 hours after thrombectomy,to observe the dynamic changes and its meaning of plasma D-lactate and serum LDH levels before and after thrombectomy.Results:During a mean aspiration time of 2.48 minutes±0.47,transcatheter aspiration embolectomy was technically successful in all 12 animal models(100%),with a mean aspirated fluid volume of 41.0 mL±4.2.Post-treatment angiography demonstrated that all the central trunks of mesenteric arteries were recanalized but residual thrombi were confirmed in segmental branches in all the 3 groups.The number of the branches which have residual thrombi was less than 4,and the branches with residual thrombi were not adjacent each other in each case.No severe complications such as vascular trauma or intestinal hemorrhage were encountered during or after the procedure in any of the dogs.In group which thrombectomy were performed 2 hours after embolism,plasma D-lactate levels reached a peak at 2 hours post-embolization just as embolization group,then fell to baseline levels after reperfusion.No significant changes of serum LDH levels were found before and after both ischemia and reperfusion insults.In group which thrombectomy were performed 4 hours after embolism,plasma D-lactate levels had a tendency to further increase after reperfusion and reached a peak at 2 hours post-thrombectomy,which were higher relative to the levels of 6 hours post-embolization in embolization group(P＜0.05),then slowly fell down to a relative higher levels 24 hours after reperfusion(P＜0.05).serum LDH levels had a tendency to further increase after reperfusion and reached a peak at 2 hours post-thrombectomy either,but lower than the levels of 6 hours post-embolization in embolization group (P＜0.05),then rapidly fell to baseline levels at 6 hours after thrombectomy.In group which thrombectomy were performed 6 hours after embolism,plasma D-lactate and serum LDH levels had a tendency to further increase after reperfusion,which were higher relative to the levels of embolization group(P＜0.05),the 4 dogs in this group died respectively at 4～6 hours after thrombectomy.Conclusion:In conclusion, manual aspiration thrombectomy with an 8Fr arterial sheath provides safe,convenient and efficient removal of fresh thrombus in superior mesenteric artery at low cost. Although transcatheter aspiration embolectomy was technically successful in all 3 groups,but the prognosis of the ischemic intestine after complete acute superior mesenteric artery embolizatioin is different if thrombectomy were performed in different pathological stage.The intestinal ischemic injury was reversible and no obvious ischemia reperfusion injury was found if reperfusion was timely obtained while ischemic injury located in mucous membrane.During ischemic injury reached submucous membrane,transitory reperfusion injury can occurred but the ischemic intestine can recover lately.Animal ususlly died of severe ischemia reperfusion injury if thrombectomy was performed while ischemic injury reached intramuscular layer, although no transmural bowel wall necrosis was developed.Plasma D-lactate and serum LDH levels continuously examined before and after interventional embolectomy in confirmed AMI cases not only can help to judge the prognosis of the ischemic intestine after reperfusion,but also help to forecast if ischemia reperfusion injury would occured and its degree,which has significant clinical value in instructing therapy and forecasting prognosis.