| Background: Ventricular septal defect(Ventricular Septal Defect,VSD)is one of the most common congenital heart defects and accounting for around 20-30%.With the aggravation of environmental pollution and increasing of elderly parturient women caused by the second child policy published by Chinese government recently,morbidity of VSDs will predictably increase obviously in the future.Surgical closure is traditional treatment of VSDs which has certain efficacy with high success rate,however,there were also many disadvantages,such as large trauma,transfusion,surgical scar,residual shunts and ventricular arrhythmia.Transcatheter closure of VSD was first reported by Lock et al in 1987 using a Rashkind umbrella device.Since then,with the development of technology and improvement of devices,transcatheter closure method had a potential to become the routine treatment of VSDs.However,the nitinol occluders which have been used most widely in clinical medicine also have some complications can’t be solved even now including complete atrioventricular block,,valve damages and hemolysis.The blood vessels of children are much thinner and more vulnerable than adults’,which are more possible to be accompanied by vessel complications.Thus,smaller diameter of sheath is needed for children.Furthermore,finer sheath should be used by retrograde method for closure of VSDs which will make the operation much easier and reduce exposure time under X-rayon children.The polyester fiber membrane structure was filled in most nitinol occluders of which main role is to block blood flow and promote formation of thrombus.However,the membrane structure needs multilayer and causes larger sheath,sometimes will also lead to fever by allergy.The ADO II occluder with no-polyester-fiber membrane structure has verified its safety and efficacy in multiple studies.However,there is still no report for VSD occluders without membrane structure.Objective: Develop a new type of non-membrane device and conveying system for closure of ventricular septal defect,test its mechanical properties in vitro and evaluate its safety and efficacy on VSD canine models established with ventricle septum puncture technology.Methods:1.The designment of a non-membrane device for VSD occlusion and its property evaluation in vitro.(1)Designment of the new device: the novel device has two plates,360 thin nickel titanium alloy wire are divided into 5 layers to weave,the center column consists of 72 wires is placing into the waist.The two ends of new occluder are frapped by the 316 L stainless steel sleeve,one of the ends is connecting with the transport pole.The occluder has 2 sizes-6 and 8mm diameter of the waist.We removed the outside spiral hoop of the transport pole to ensure it can pass the 5F catheter and reduce the tip of the load sheath to8 mm to fit with the Guiding catheter perfectly.(2)To evaluate the mechanical property of the new device and system,including its tension detection,elastic recovery,capacity load of hydrostatic pressure.2.Animal experimentation of the VSD occlusion system in canine model:(1)the establishment of VSD model through internal jugular vein.(2)The establishment of internal jugular vein-VSD-femoral artery loop,taking the retrograde transarterial approach for the closure of VSDs.(3)after the procedure,canines are administrated by aspirin 3-5mg/Kg/D tills the last follow-up.(4)Follow up: Observe the success rate of the operation and the complete occlusion of VSDs at once.Canines are sacrificed at 4,8,12,24 weeks after the procedure for observed,including the general condition,ECG and chest fluoroscopy,LV angiography,observation of gross specimens and pathological sections,and to analyze the effectiveness,such as the success rate of the operation,the endothelializationand complete occlusion rate of the VSD,and also the safety concerns,including complete atrialventricular block,residual shunts,valve damages,device embolism,hemolysis,and so on.3.statistical processing: using the SPSS20.0 statistical software for statistical analysis of the data.The measurement data is expressed by X ±s,and the count data is expressed as the rate.Analysis using T test or chi square test and Fish exact test methods,P value 0.05 for the difference was statistically significant.Results: 1.The preparation and detection of the novel device in vitro:(1)The tension of pulling the non membrane 6mm occluder and the with membrane 6mm occluder to 16 mm were 0.635 ± 1.97 N and 2.215 ± 0.20N(p<0.001),respectively.The result demonstrated the quality of None membrane 6mm occlude is more soft than the with membrane 6mm occlude’s.Occluders can convey,release,and recycle by 5F catheter easily.Keep the 6mm and 8mm occluder in the sheath tube dipped in 37 ℃ water bath for 15 minutes then release them,the shape recovery ability of left piece were 98.39%,97.99%,respectively,and the right side were 92.23%,91.28%,respectively.The capacity of the resistance against water was detected by the time of water flowing from the 5cm H2 O altitude to the bottom.The data were 17.59±0.75 s,17.44±1.26 s,(p=0.750)for the with-membrane 6mm occlude and non-membrane 6mm occlude,respectively.The statistical different between the groups had no significant.(3)Occluders were transported,released and withdraw in 5/6F delivery sheath for 20 times without abnormal condition.The tips of the sheath were normal without damage.Because of the soft tip of the guiding catheter,it was deformation when the 8mmocclude withdraw into the 6F guiding at the 12 times.The connection of Load sheath and the end of guiding pipe was normal.We confirmed the delivery system was stable and feasible.2.Transcatheter closure of ventricular septal defect with non-membrane device in canine:(1)The establishment of VSD model: 14 canine model was successfully established in 16(87.5%),1 cases died of pericardial tamponade,1 cases died of ventricular tachycardia during VSD puncture.The anatomy shows the distance from VSDs to aortic valves were 4-10mm(n=10),average 6.35 ± 1.84 mm,to the three tricuspidvalves were 1-5mm,average 3.15 ±1.33 mm,shows the type of VSDs were perimembranous which has a good value for estimate.(2)Retrograde method for VSD occlusion: 12 cases of experimental dogs using retrograde by lateral aortic occluder selected conveying 5F guiding catheter,the success rate of 100%,the improved transportation system and guide catheter were connected normally.The method is reliable and safe.(3).Transcatheter closure of VSD,The success rate of the procedure is 92.86 %(13/14),1 cases died due to deep anesthesia.2 cases were using 8mm occluder,12 cases were using 6mm occluder.Only 1 case have mild residual shunt,immediate complete closure rate of 92.30%(12/13),after ten minutes follow up the residual shunt was disappeared,there was no arrhythmia,no other special complications.(4)Follow-up: 2 cases appears gross hematuria,but recovery within 1 week,2dogs were sacrificed 2 weeks,4 weeks,8 weeks,12 weeks,and and24 weeks after the procedure.ECG of all the dogs showed no AV block,the left ventricular angiography didn’t show any residual shunt and aortic valve insufficiency.The anatomy was observed in different follow up points,no device ectopic and thrombosis,no major organ embolism.The endothelialization of device was developed gradually at different time points.(5)Pathological examination: The tissue of device surface showed few endothelial cells at 4 weeks,endothelial cells grew well at 8-24 weeks,with regular arrangement.Conclusion: The 6mm and 8mm none polyester fiber membrane ventricular septal defect occluder can convey,recovery,and release by 5F and above catheter,may make great contribution to reduce the risk of vascular complications.Animal experiment showed a high complete closure rate,the effect of blood-block had no significant difference with device with-membrane.Transcatheter closure for VSD by the occluder and its system has a high success rate,less complications,and a reliable short and mid-term effect. |
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