Evaluation Of New Device For Closure Of Perimembranous Ventricular Septal Defect In A Canine Model

Objective:To evaluate the safety ,efficacy and feasibility of transcatheter closure ofventricular septal defect(VSD) with new-type occluder in a canine model. Material and Method: 1.Construct a new ventricular septal defect occluder andobserve biocompatibility of nitinol alloy: Nitinol wires were detected by SMA-1analyser and observed by scanning electron microscopy. Human fibroblasts were incubatedwith nitinol alloy. OD value was detected by MTT spectrometry.New occluder were wovenby nitinol wires and formed into two-disc-shaped device by heat treatment. 2.The creationof VSD in a canine model. 10 dogs underwent transcatheter ventricular septal puncturewith Brockenbrough puncture needle via right jugular vein under fluoroscopy,and dilatedthe defect with 6-8mm balloon catheter.Left ventricular(LV) angiography was performedwith pigtail catheter by transaortic access.Right after operation and 1-4 months later,thedogs were killed and the defects were observed.The serum concentration of nitinol wasdetected by Zeeman graphic furnace atomic absorption spectrometry before and afteroperation.3.Experimental study of the new-type occluder:VSD was closed by occludervia 7F delivery sheath under fluoroscopy in the catheterization laboratory.The location ofdevice and function of tricuspid valve(TV) and aortic valve(AV) were observed byventricular angiography and echocardiography.1,2,3,4 months later,the animals were killedand autopsy.the tissue sample were obtained for pathologic examination. Result: The concentration of nickel was 55.6%-56%,titanium 43.5%-44%. Theconcentration of Pb,Sb,Sn,Bi and As were all below the national standard.The nitinol wireswere stretched 7.02 ± 0.34% when broken at 1399 ± 9.83Mpa. Compared withimported wires which were stretched 4.50±0.08.% at 1402±9.59Mpa,self-made nitinolwires had good stretching ability(p<0.01).The nitinol alloy had no effect onproliferation of human fibroblast.Compared OD value of nitinol group (0.798± 0.101) with contrast group(0.776 ± 0.088),there was no significantdifference(P>0.05) The surface of wire was smooth under scanning electronmicroscopy.The new VSD closur device can be stretched into an almost linearconfiguration and placed inside a small sheath for delivery, and then reform to its originalconfiguration when released. 10 dogs underwent transcatheter ventricular septal puncture 3with Brockenbrough puncture needle via right jugular vein under fluoroscopy,and dilatedthe defect with 6-8 balloon catheter.Left ventricular(LV) angiography was performed withpigtail catheter by transaortic access after puncture.After operation and 1-4 monthslater,the dogs were killed and the defects were observed.Recults:VSDs were successfullymade in 8 dogs,which demonstrated by LV angiography.1dog had defect at membranouspart.The defects in other dogs located near membranous septum or muscular septum not faraway from membranous part.The distance from Aortic valves to the rims of defect was4-16mm,from tricuspid valves 4-10mm. 6 dogs which had VSD produced by punctureunderwent VSD closing procedure successfully.The defect located near membranousseptum,similar to paramembranous defect in humanity.The occluders,which well locatedwith disks astride the defect,had no influence on the function of TV and AV in epicardialechocardiogram and ventriculogram.Gross examination of the occluder revealed no wirebreakage or fracture of the device.Looking from both side,the devices were covered with asmooth intact neointimal layer in all dogs.Endothelium were partially covered on thesurface of occluder in dogs killed after 1 month,and fully covered in those killed after 3months,which demonstrated by light and electron microscopy,there was no evidence ofcorrosion on the surface of the nitinol wire removed from the dog after 4 months.Theconcentration of nitinol after operation 1,3month (0.68±0.52ug/L,2.05±1.43ug/L)were significantly higher than before operatio...