Evaluation of in vivo biocompatibility of different devices for interventional closure of the patent ductus arteriosus in an animal model

Objective-To evaluate the in vivo biocompatibility of three different devic es following interventional closure of a patent ductus arteriosus (PDA) in an animal model. Materials and methods-A medical grade stainless steel coil (n = 8), a nicke l/titanium coil (n = 10), and a polyvinylalcohol foam plug knitted on a tit anium wire frame (n = 11) were used for interventional closure of PDA in a neonatal lamb model. The PDA had been maintained by repetitive angioplasty. Between one and 278 days after implantation the animals were killed and th e ductal block removed. In addition to standard histology and scanning elec tron microscopy, immunohistochemical staining for biocompatibility screenin g was also undertaken. Results-Electron microscopy revealed the growth of a cellular layer in a co bblestone pattern on the implant surfaces with blood contact, which was com pleted as early as five weeks after implantation of all devices. Immunohist ochemical staining of these superficial cells showed an endothelial cell ph enotype. After initial thrombus formation causing occlusion of the PDA afte r implantation there was ingrowth of fibromuscular cells resembling smooth muscle cells. Transformation of thrombotic material was completed within si x weeks in the polyvinylalcohol plug and around the nickel/titanium coil, a nd within six months after implantation of the stainless steel coil. An imp lant related foreign body reaction was seen in only one of the stainless st eel coil specimens and in two of the nickel/titanium coil specimens. Conclusion-After implantation, organisation of thrombotic material with ing rowth of fibromuscular cells was demonstrated in a material dependent time pattern. The time it took for endothelium to cover the implants was indepen dent of the type of implant. Little or no inflammatory reaction of the surr ounding tissue was seen nine months after implantation.