| Background: Foramen ovale is an interatrial communication that is needed during the lifeof the fetus as it facilitates the passage of umbilical vein blood from the right atrium to theleft atrium to maintain the fetal circulatory system.Immediately after birth, the forming pulmonary circulatory system producesfunctional closure of the foramen ovale. Closure occurs immediately after the cellulosecoherence to the foramen ovale within the first years postnatally in about25%of all infants.Patent foramen ovale is a congenital cardiac lesion that functional closure does not occurafter3years old and the foramen ovale remains permeable into adulthood. In normal,theleft atrial pressure is higher than that of the right atrial.The flap is lightly pressed againstthe septum secundum without no shunt. This kind of PFO has no pathological andphysiological repercussions.When right atrial pressure increases,the flap will open,it will cause a right-to-leftshunt,being as a conduit for paradoxical embolism.The possible association of PFO withcryptogenic stroke, transient ischemic attack, migraine,decompression sickness in divers,platypneaorthodeoxia syndrome,or mountain sickness has been reported.In patients withclinical signs and symptoms of PFO,percutaneous closure could be considered thetreatment of choice for those receiving surgical and medical treatment.Many devices have been used for percutaneous PFO closure: the Amplatzer device is oneof the most frequently used with in percutaneous treatment,with large amount of devicesused, significant results and fewer complications.Owing to the desigh defects of someoccluders, neoendothelialization of the decices is of major clinical relevance because ofsuperficial thrombus formation.Thrombus formation can occur with any occluder rangingfrom0.8%-7.1%.To further optimize the structure of the existent PFO devices,we designedand produced a new type of PFO occluder, left-disk with non-hub occluder device throughan entirely neoteric knitting method in cooperation with Shanghai Shape Memory AlloyCO.,Ltd. The novelty is that the left atrial disc of the occluder consists of a planus discwith non-hub on the central side which therefore may induces fast and completeendothelialization,decreases superficial thrombus formation.Objective: To evaluate the feasibility, efficacy, and safety of transcatheter implantation of a patentforamen ovale (PFO) device consisting of a left disk with no hub in an animal model, in an attempt toprovide preliminary experimental clues for further clinical research and application of the device.Methods:22healthy adult dogs were selected to establish a dog PFO model by percutaneous puncture of the atrial septa and balloon dilation of the fossa ovalis. Two dogs were selected randomly forpathological examination via the point punctured with a transseptal needle. The reaming20dogs wereequally randomized to two groups: one group using the PFO occluder with a left disk with no hub, andthe other group using the double-hub occluder as control. Dogs were sacrificed at1,2,3and6monthsafter device implantation to obtain tissue samples for gross examination, histological evaluation,immunohistochemical stainings and SEM examination to evaluate endothelialization afterimplantation of the new type occluder, observe complications including residual shunt and superficialthrombus formation.Results:The PFO model was established successfully by percutaneous puncture of the atrial septa andballoon dilation of the fossa ovalis. Angiography of the right atrium showed that the contrast mediumflew from the right atrium into the left atrium. Gross examination of the samples from the two dogsshowed that the cardiac pericardium was intact. The size of the fossa ovalis defect in the two dogs was5mm×6mm and6mm×6mm respectively. A little amount of ecchymosis was observed around the fossaovalis defect, and no thrombus formation was observed. The rest of the endocardium was intact.Implantation of the PFO occluder with a left disk with no hub was successful in all10animals (100%),while implantation of the double-hub occluder was successful in9animals (90%). The19dogs weresacrificed at1,2,3and6months after device implantation. The tissue samples showed no dislocation ofPFO occluders in both groups, nor was there fracture of the nitinol wire. No superficial thrombusformation or ecptoma was observed. The surface of the bilateral disks of the occluder in the study groupwas covered mainly with lamellar lucency tissue. Histological and SEM examinations revealed that thesurface was composed of fibrous tissue and endothelial cells. There was no thrombosis or ecptoma.The tissue overjut on the surface of the occluder was gradually thickened after operation, and the edgeof the occluder fused with the adjacent cardiac tissue. In control group, the surface of the left disk ofthe occluder was covered main with fibrous tissue and endothelial cells, except the hub in the center ofthe occluder. No tissue overjut was observed on the surface of one occluder in control group at6months after the procedure.Conclusion:(1) The way that we select dogs to establish dog PFO model by percutaneousfossa ovalis of atrial septal puncture and balloon dilation is feasible.(2) The new PFOoccluder with a left-disk with no hub is feasible for percutaneous closure of PFO. Compare with thedouble-hub PFO occluder, the new device shortened the time of complete endothelialization and decreased the occurrence of complications, thus having the potential for clinical application. |
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