Experimental Study Of False Lumen Embolism For Treatment Of Distal Aortic Expansion After Dissection

BackgroundAortic dissection(AD)is a life-threatening cardiovascular disease associated with high rates of mortality and morbidity.Current surgical treatments such as open surgery or endovascular repair are usually reserved for proximal tears,while most distal tears are treated conservatively.However,the results of long-term follow-up show that there are some patients with distal aorta dilatation or even rupture due to the presence of distal tear and continuous blood flow impact.In recent years,more and more scholars are exploring the treatment of distal tears in patients with AD.Traditional thoracoabdominal aortic replacement is widely used around the world as first-line treatment for patients with post-dissection aortic aneurysm,but featuring heavy trauma,higher incidence of complications and operative mortality.It is also not suitable for some elderly and frail patients.At present,the methods of endovascular repair for distal tears are mainly divided into true lumen approach intervention and false lumen approach intervention.The true lumen intervention includes fenestrated and branched endograft,parallel stent-graft technique and multilayer bare stent technique,and false lumen intervention is mainly mainly involves filling or occluding the false lumen,such as coil,occluder,iliac artery stent,etc.However,distal tears often involve the visceral artery segment.Endovascular repair requires the reconstruction of the branch visceral artery,which is relatively difficulty and can only be carried out in some large centers.Based on the existing endovascular repair,a porous graft is used to fill the false lumen,which can change the local flow and promote the complete thrombosis of the false lumen.In this way,the blood flow to the false lumen is interrupted and benign remodeling of the distal dissection is promoted.Objective1.Comparing the different prognosis of AD,using computational fluid dynamics to explain the hemodynamic factors of distal aortic expansion after dissection.2.Retrospectively analyze the different treatment methods of distal aortic expansion after AD in our center,and evaluate the effect of assisted false lumen embolization in the treatment of distal expansion after dissection.3.Based on the dissection model,evaluate the effect of porous graft in vitro.4.Construct an animal model,complete the porous graft release,and explore the safety and effectiveness of the porous graft in the treatment of distal aortic expansion after AD.Methods1.Based on computational fluid dynamics,construct characteristic aortic dissection,and simulate the hemodynamic characteristics of different prognosis of dissection,which providing the formation mechanism of distal expansion after dissection.2.Retrospectively analyze the data of patients with distal aortic dilatation after AD in our center from January 2015 to September 2019.Aortic remodeling and reintervention are compared in different groups to evaluate the safety and effectiveness of assisted false lumen embolization.3.Use soft silicone material to print a transparent,low-refractive-index model of distal aortic expansion after dissection,and evaluate the effect of different porous grafts under the action of an extracorporeal circulation pump.4.On the basis of the porosity screened out by the above in vitro experiments,the corresponding animal model is established to verify the safety and effectiveness of the porous graft in the treatment of distal aortic expansion after dissection.Results:1.Using computational fluid dynamics methods,construct characteristic models of patients with different prognosis.In the poorly remodeling model,there are more areas of high wall shear.The pressure distribution of false lumen in the levels of proximal tear,distal tear and renal artery is higher than that with good remodeling model.2.A total of 70 patients were enrolled from January 2015 to September 2019,of which 51 are in the assisted false lumen embolization group(group A),and 19 patients receive thoracic aortic stent/abdominal aortic stent implantation(group B).There are no perioperative deaths in group A.The average follow-up time is 34.5±16.0 months.Three patients die(1 dies of intestinal obstruction,1 dies of aortic rupture,and 1 dies of infectious aortic aneurysm).Endoleaks occur in 6 patients and are treated with coil embolism.Two patients receive re-intervention due to stent-graft stenosis/occlusion.One patient has a new tear at the distal end of the stent-graft and receives conservative treatment.One patient developes arrhythmia,and the symptom is relieved after radiofrequency ablation treatment.The average follow-up time of group B is 41.4±19.5months.In group B,1 patient dies of gastric cancer.Three patients receive re-intervention due to endoleak.One patient is converted to open surgery due to retrograde AD.There is no significant difference in the postoperative re-intervention rate and survival rate between the two groups.In group A,the aorta remodels well in the levels of the end of the stent,celiac axis,and the bifurcation of the abdominal aorta.The true lumen is expanded and the false lumen is reduced.In group B,the three levels only show true lumen expansion,and there is no significant difference in the changes of false lumen diameter and aortic diameter.3.Use 1:1 licone material to make a model of distal aortic expansion after aortic dissection.Under the action of an external circulation pump,the release of porous grafts with different porosities is successfully completed.It wass found that porous grafts can effectively embolize and reduce blood perfusion in the false lumen.4.Perform aortic bypass modeling on 7 healthy animals,of which 1 animal died after surgery,and 6 were successfully modeled.Postoperative CTA indicates that the aortic bypass is patency.The porous grafts are successfully released in the remaining 6animals,and the immediate intraoperative angiography shows that the embolized segment of the aorta was not visible.Afer intervention,5 animals survive and 1 animal die of septic shock.Follow-up ultrasound shows that the porous grafts are in place,and there is no obvious blood flow signal in the embolized segment of the aorta.All branch visceral arteries and aortic bypasses are unobstructed.ConclusionThe current incidence of distal dilatation after aortic dissection gradually increases,and there are greater difficulties in the treatment of open surgery or endovascular repair.In these cases,a porous graft is proposed to induce false lumen thrombosis by occlusion of the false lumen,providing a new option for distal aortic dilatation after dissection.In addition,in vitro experiments and animal experiments has preliminarily verified the feasibility of porous graft,and the outcomes are acceptable in the perioperative and follow-up period.