The Design And Manufacture Of A New Type Integrated Two-branched Stent Graft And The Deployment Research In Vitro

BackgroundAortic dissection and aortic aneurysm is a very horrible disease which seriously threat to human's health and survival.Due to some reasons,such as satisfactory short-term results,minimally invasive and fewer complications,EVAR has gradually become the main treatment of aorta disease and trauma since the first application in 1991.The indications have been developed to aortic aneurysm,aortic dissection,traumatic aortic disease and other aortic disorders of descending thoracic aorta and abdominal aorta.However,EVAR encounters obstacles in treatment when aortic lesions and trauma involving aortic arch and vital aortic arch branches.Vital branches,large bending,high pressure and high speed blood flow are all important problems need to consider clearly for EVAR.With the development of new type of non-standard stent grafts,it is impossible to repair lesions and trauma of aortic arch with EVAR.A new type of stent graft should be designed first,and after repeated cycle of modified-test,and then could be applied to clinic.In the present,the improvement of new stent graft in the process of research and development are based on a large number of animal experiments.However,the process of new stent graft design improvement using large animals is costly and the animal utilization rate is pretty low.Aorta rupture caused by death when new stent graft deployed always happens especially in the early improvement stage.Furthermore,the morphology of stent graft and the relationship between stent graft and aortic branches after deployment could not be observed directly and must use X-ray fluoroscopy or vascular ultrasound.At last,new stent graft could not easy to take out after deployment in animals' aorta and the endograft utilization rate is also very low.All these have brought considerable research and development costs.In order to solve these problems,a new type of integrated two-branched stent graft which was advantage to the reconstruction of aortic arch with totally minimally invasive method was developed.At the same time,this research also designed a kind of canine thoracic aorta deployment simulation device,which could simulate the shape and location of canine aortic arch and its branches.This canine thoracic aorta deployment simulation device was transparent,and could be visualized clearly under X-ray fluoroscopy to simulate the deployment process.Part one The design and manufacture of new type integrated two-branched stent graftObjectiveTo design and manufacture a new type integrated two-branched stent graft which was suitable for experimental beagles within the scope of weight range form 11 kg to 15 kg.Methods1.DesignNew type integrated two-branched stent graft included an integrated stent body and two branches arised from stent graft body.The initial segment of these two branches located in the upper part of beginning of aortic arch branches separately when this new type stent graft was fully expanded and properly positioned.The next,two small straight tubular stent grafts were land with new stent graft branches separately so that this new type integrated two-branched stent graft could successfully reconstruct the canine aortic arch.This design did not need absolute precision when deploying,reduced release time and difficulty greatly and simplified operation steps.2.Manufacture2.1 The manufacture of new type integrated two-branched stent graft2.1.1 Materials and equipmentsNickel titanium alloy wave rings in shape Z,artificial graft made in polytetrafluoroethylene,metal tags enhanced under X-ray,vascular sutures,16-slice computed tomography,digital subtraction angiography system,and high pressure syringe.2.1.2 ManufactureThe body of new type integrated two-branched stent graft included anterior section,median section and posterior section.The anterior section was proximal part of new stent graft and arised first branch of new stent graft in the end.The median section was a continuation of the anterior section and arised second branch which was 25 to 30� angle to the body of stent graft.The posterior section was distal part of new stent graft.2.2 The manufacture of small straight tubular stent graftsThe use of materials was as same as the new type integrated two-branched stent graft.Its production technology was consistent with the clinical use.ResultsA new type integrated two-branched stent graft and two small straight tubular stent grafts were made.The Former included two branches and a stent graft body which could reconstruct the canine aorta.There were eight markers which could be view under X-ray fluoroscopy in this stent graft.The latter was straight tubular and there were two markers which could be view under X-ray fluoroscopy.ConclusionsThe product of new type integrated two-branched stent graft and small straight tubular stent grafts were made and provided the materials for next experiments.Part two The manufacture of canine thoracic aorta deployment simulation deviceObjectiveTo design and product canine thoracic aorta deployment simulation device and this device was suitable for deployment of new type integrated two-branched stent graft.Methods1.Materials and equipmentsTwo pieces of acrylic squares,aluminium wire of 1 mm in diameter,fixed screws,DELL INSPIRON 1420,Windows 7 ultimate,UG-nx 8.0,16-slice computed tomography,digital subtraction angiography system,and high pressure syringe.2.The manufacture of canine thoracic aorta deployment simulation deviceThe initial state of canine thoracic aorta flat image was create using UG-nx software which could help us to design the shape of canine thoracic aorta in Three-dimensional(3D)modeling used 3D visualization techniques.In the next moment,the 3D image of canine thoracic aorta was formed through the software analysis and started to optimize as well as adjusted the local parameters.A diameter of 1 mm aluminium wires were paste around the lateral side of half of vessel lumen which outer edge had been dug up a 1mm�1mm square groove.And then,the sample model of canine thoracic aorta tube was been builded and submitted orders to machinery manufacturer and produced the product.ResultsThis deployment simulation device was rectangular in shape and made by polymethyl methacrylate(PMMA).A semicircular cavity was been dug out within each piece of organic glass inside according to the canine thoracic aorta anatomical morphology.A diameter of 1 mm aluminium wires were paste around the lateral side of half of vessel lumen which outer edge had been dug up a 1mm�1mm square groove.This deployment simulation device was cubic and transparent.The inside hollow tube was been view as the shape of canine thoracic aorta under direct observation and X-ray fluoroscopy.ConclusionsThe product of canine thoracic aorta deployment simulation device was made and provided the materials for deployment research of new type integrated two-branched stent graft.Part three The deployment research of new type integrated two-branched stent graft in vitro and the improvement of the stent graftObjectiveThe deployment research in vitro would help us to found problems when deploying and docking of new type integrated two-branched stent graft and small straight tubular stent grafts.There would be put forward revision proposals and improve the stent graft design.Methods1.MaterialsOne new type integrated two-branched stent graft within 21-Fr delivery sheath,two small straight tubular stent grafts within 16-Fr delivery sheath,and one canine thoracic aorta deployment simulation device,three super smooth guidewires,three stiff guidewires,three 5-Fr marked pigtail catheter,digital subtraction angiography system,and high pressure syringe.2.Experimental methodNew type integrated two-branched stent graft was introduced from the descending aorta tube under X-ray fluoroscopy.The delivery system was advanced into the ascending aorta tube along the stiff guidewire and observed maker of new type integrated two-branched stent graft under X-ray fluoroscopy.In an ideal position,the outer sheath was pulled back slowly and then two branches of new type integrated two-branched stent graft were deployed.Small straight tubular stent grafts were introduced from brachiocephalic artery tube and left subclavian artery tube into stent graft body respectively.One of small stent grafts was landing at first branch and brachiocephalic artery tube.The other was landing at second branch and left subclavian artery tube.Thereafter,removed out the delivery sheath and stiff guidewire and all operation ended.3.Success criteria of deploymentThe experimental success criterion of new type integrated two-branched stent graft was successfully deployed in canine thoracic aorta deployment simulation device without shift,docking success,the delivery sheaths and guidewires removed smoothly,the shapes of stent grafts were good,all stent grafts jointed closely with aortic tube in anchoring zone.And the connections between stent grafts were tight.ResultsThe delivery sheath could not be sent to the ideal location because of the ascending aorta tube was too short and the second branch was so long that the end of this branch got into the brachiocephalic artery tube after deployed in five preliminary experiments.Therefore,the ascending aorta tube length was increased and the lengths of the two branches were shortened.Eight deployments were successful in fifteen formal experiments.The new type integrated two-branched stent graft was successfully deployed in canine thoracic aorta deployment simulation device in the formal experiments.ConclusionsThe new type integrated two-branched stent graft could successfully reconstruct the aortic arch tube in canine thoracic aorta deployment simulation device.The design requirement of this stent graft was reached basically.At the same time,the problems of stent graft were discovered and solved through experiments in vitro.