| Background and Objective: Congenital heart diseases (CHD) are themost common pediatric heart diseases. Isolated ventricular septal defect(VSD) is the most common congenital cardiac malformation, accountingfor 20% of all instances of CHD. It is estimated that there are30,000-50,000 newborn infants with VSD each year. In the past, surgicalrepair was the only method to solve the problem, but it brought patientsphysical and mental sufferings, such as surgical trauma, long length of stayin the hospital, scars and so on. So surgical repair is not an ideal means. Allinterventional therapies remain a challenge to both the cardiologists andsurgeons. Since Lock et al reported the first transcatheter closure of VSDusing Rashkind umbrella in 1988, then Clamshell,CardioSEAL,Sederisbuttoned VSD devices have been implanted with poor results whichincluded complicated manipulate, large residual shunt and highcomplications, so restricted widespread application in patients. It is notrapid until the Amplatzer VSD occluder and its delivery system emerge in2001. Amplatzer VSD device has many advantages, such as small volume,complete retrievability before release and compete closure etc.It isgenerally accepted by doctors and patients, but these devices have not beenwidely used in China because of the expensive price. For the past few years,several kinds of domestic VSD occluders have been produced and spreadedrapidly, but it is a concerned issue for their biocompatibility and safety.Our experiment was to evaluate a new homemade VSD occluder in acanine model according to closure effect and histology observation, make aprimary study of feasibility, safety and therapeutic effect. Method: 12 dogs were prepared for the experiment, animal modelswith VSD were established by surgical methods without extracorporealcirculation, then homemade VSD occluder was implanted directly duringthe surgical procedure, then the dogs received hypodermic injection heparin100u/kg/d for one day, and aspirin 5mg/kg/d, oral administration tillexperiment is over. These dogs were divided into four group randomly andobserved by transthoracic echocardiogram at 15days,1,3,6months afteroccluder implantation, then they were killed for histological observation bygroup respectively. Results: VSDs and successful implantations of the device wereachieved in 8 dogs. Macroscopic examination showed that there were noneoplasm, thrombus, fractures and corrosion except one dog had aneoplasm because of infective endocarditic. Postmortem gross andmicroscopic examination of devices showed that all the right and leftventricular discs of the occluder were completely covered by a layer of newendocardium. Fibrous tissue and endothelia cell were seen through lightmicroscopy and electron microscopy. There was inflammatory reaction inearly period and decreased gradually. Three months after implantation, theoccluders were mostly endothelialized and there are myocardial cells andblood vessels at the edges of the device. Six months after implantation, thedevices were completely covered with endocardium. The inflammatoryreaction diminished with a few chronic inflammatory cells still existing.Embolization in lung, liver, spleen, kidney was not found in all animalsafter device implantation. Conclusion: The homemade VSD occluder devices have manyadvantages, such as self-centering, self-expanding, complete retrievability,easy deployment, good biocompatibility,etc. It is feasible and safe toestablish by surgical methods and perventricular closure of VSD. Itprovided an evidence of animal experiment that if the infant is small in size,precluding safe percutaneous closure, or if the muscular VSD is associatedwith other defects requiring open surgical repair (pulmonary arterydebanding, double-outlet right ventricle, transposition of the great vessels,etc), closure of the VSD can be achieved in the operating room prior toinitiation of cardiopulmonary bypass.
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