Designs And Manufactures Of Medical Polyester Coated Nitinol VSDO And Its Animal Experiment Research

Background: Amplatzer ventricular septal defect(VSD) closure devices have beenwidely used in recent years, and transcatheter device closure of VSD has become aoptimal treatment of selected patients because of its slight trauma, high safety andideal efficiency. But at present, the nitinol wire VSD occluder still exists defects. It canresult in the conduction system block, valvular damage because of hard nitinol directcontact with local organizations, and in addition, the time of VSD occluder (VSDO)endothelialization of requires2-3months, or longer. To maintain the same dual-diskstructure of the Amplatzer occluder, domestic and foreign scholars have improved thematerials or waist structure in order to prevent intervention-related complications afterclosure VSD. There are five types of these occluders:1zero rim, symmetric orsmall waist large rim VSDO;2porcelain coated VSDO;3pan-nitinol stainless steelbuttom-removed VSDO;4bioabsorbable vsdo;5waist length adjustableVSDO.However, These occluders can not fundamentally solve the nitinol occluderdirectly with the contact of blood and tissue, leading to edema, scar formation, thrombusattached set of defects caused by complete atrioventricular block, aortic rupture,thromboembolism, hemolysis, and other serious complications.For the above purposes, we designed the medical polyester thread woven coatednitinol VSDO. Fist, the aim of the design is to reduce the VSD after transcatheter closureof conduction block, because the polyester overcoat cushion between the myocardial tissueand hard nitinol, to reduce tissue tension, reduce inflammation, reduce scarring; Second,polyester overcoat can prevent long-term direct friction of the nitinol wire on themyocardial tissue, destruction of normal myocardial tissue; The last, polyester overcoat canshorten VSDO endothelial cells time.Objective: To design medical polyester thread woven coated VSDO, Evaluation of thephysical properties of the polyester coated VSDO, To evaluate the safety, efficacy andfeasibility of transcatheter closure of VSD with the polyester coated VSDOs in a caninemodel. Comparison of myocardial tissue reaction, endothelialization process andbiocompatibility at different time points in the polyester coated VSDOs goup andconventional VSDOs in canines.Method:1Design of medical polyester coated ventricular septal defect occluder:The shape wax model was made in accordance with the conventional VSD occluder slightlystretch the shape. After the wax model fixed on the weaving machine, the weavingmachine axle travel speed were set to pitch0.2mm, walking speed0.2mm/s respectively,to make into a wax model-polyester envelope compomer using the medical4-0suturesto the warp knitting on the wax model. The final steps of in this procedure ware to usevegetable oil dewaxing, alkyl sulfonate off grease, then the Polyester envelope wasproduced successfully. Conventional nitinol VSD occluder were delivered to theenvelope by the the sheath. It should be the match between the polyester envelope waistand disc position and the occluder, then and polyester external envelope both ends of thesuture on the VSD both ends of the rivets, the high temperature knife cuttingend ofsurplus part. Two sides of the polyester envelope was sutured at the VSD stainless steelrivets, and both ends of the surplus part cut by high-temperature knife.2Testing thephysical parameters of medical polyester coated ventricular septal defect occluder:16conventional VSDOs were randomly assigned to two groups, which one group(n=8)was made into polyester coated VSDOs, as polyester coated VSDOs group, anothergroup as a conventional occluder group.①Measuring the two groups VSDOs diameter,minimum diameter of the the delivery sheath;②Testing tension of the two groupsVSDOs under different deformation state, to wonder polyester envelope whether theimpact of the the VSDOs hyperelastic;③Observing polyester coated VSDOs surfacewear status by the eyes and microscope after withdrawal-release of50in the sheath invitro;④Taking the lowest centrifugal liquid to observe whether the tiny desquamationby microscope after withdrawal-release of50in tube saline liquid.3Transcatheterclosure of ventricular septal defect in a canine model:①The creation of VSD in acanine model.18dogs underwent transcatheter ventricular septal puncture withBrockenbrough puncture needle via right jugular vein under fluoroscopy,and dilated thedefect with8mm balloon catheter.Left ventricular(LV) angiography was performed withpigtail catheter by transaortic access.②Experimental study of the polyester coatedVSDOs:VSDs were closed by the polyester coated VSDOs via10F delivery sheathunder fluoroscopy in the catheterization laboratory,and by conventional VSDOs via8Fdelivery sheath.The location of device and function of tricuspid valve(TV) and aorticvalve(AV) were observed by ventricular angiography and echocardiography.①TTE observed occluder position estimate mural thrombus, tricuspid valve, aortic valve.②Dogs were administrated with aspirin and sacrificed in1week,1,3,6monthsrespectively after devie implantation, while tissue samples were obtained forhistopathology examination.Result:1. The use of the weaving machine and warp knitting method can successfullymake polyester envelope of VSDO. Its waist diameter of8mm and disc diameter of12mm can completely fit with the diameter of8mm conventional nitinol VSDO. Thepolyester envelope was sutured tightly with the VSDO with suture method, and usinghigh-temperature knife enable surplus part of two sides of the VSDO smooth,solidification, no loose wire.2.①The diameters of polyester coated VSDOs are largerthan conventional VSDOs by0.5mm, required a minimum of10F sheath to delivery, ascompared with the conventional VSD occluder requires8F sheath.②The tensions oftwo groups of occluder have no statistically significant difference in the deformationprocess of1.25,2.5,3.75,5,6.25,7.5,8.75,10,11.25,12.5,13.75and15mm.③Thepolyester coated VSDOs were showed no obvious wear and tear by eyes, and thesurfaces not significantly different by stereomicroscope before and after the release–delivery.④There were no tiny desquamation in Saline stretch in lowest centrifugalliquid of both of two groups.3.18dogs underwent transcatheter ventricular septalpuncture with Brockenbrough puncture needle via right jugular vein underfluoroscopy,and dilated the defect with8mm balloon catheter.Left ventricular(LV)angiography was performed with pigtail catheter by transaortic access after puncture.2of18dogs died because pericardial tamponade during the procedure and1died becauseIII o atrioventricular block.8of15dogs implanted of polyester coated VSDOssuccessfully, and7dogs of conventional VSDOs. There were no complicationslong-term survival. TTE found occluders in good position, no shift, mural thrombus, noeffect on the heart valves after intervention one month. Postoperative naked eyesobserved, scanning electron microscopy, and histopathological examination occluder.Dogs were sacrificed at the diferent time points.The occluders had been covered by thefibrin membranes after postprocedure the first week, and endothelialization completely inthe first month in the the polyester coated VSDOs goup by eyes observed, scanningelectron microscopy, and histopathological examination. Nevertheless, the conventional occluders had no any membranes formation, been covered by the fibrin membranesafter the first month, and endothelialization completely in the third month. Fibrous scartissue reduced significantly in the polyester coated VSDOs in the third month and sixthmonth. The VSDOs in two groups had good biocompatibility.Conclusion:1. The polyester envelope of VSDO can be weaved by the weaving machineand warp knitting method, then the polyester coated VSDO can be successfully made bysuture.2. Various physical parameters are not significantly different in comparison ofpolyester coated and conventional VSDOs, so the polyester coated VSDOs can besafely to implant in animals.3. The polyester coated VSDOs closure device can be usedto closure canine VSD model using method of transcatheter intervention.4. Theendothelialization time of polyester coated VSDOs is shorter compared withconventional occluder in a canine model in vivo, and myocardial scar formation aroundthe polyester coated VSDOs is also significantly reduced.So this new occluder haspotential application.