The feasibility and safety of transvenous closure of atrial septal defects by a new device was tested in 20 piglets, in which atrial septal defects were created by foramen ovale dilatation with angioplasty balloons. The device was small enough to be introduced in a 7F or 8F sheath, and it measured 20-25 mm. It has no hooks and consists of a foam occluder from the left atrium and a counter-occluder from the right atrium, buttoned independently. The animals were observed by angiography and color flow mapping, and they were electively killed at various intervals up to 2 months after occlusion. The device was not thrombogenic and had endothelialized by 2-3 weeks. All atrial defects were found to be completely occluded. Complications occurred only with the first three prototype devices, including counter-occluder detachment, right atrial perforation, and need for double occlusion and pulmonary artery embolization. No such complications occurred in the last 17 experiments because of modifications of the device and operator experience. These observations showed the feasibility of occlusion of moderate-size atrial septal defects in piglets by a new device introduced through a small sheath. The method appears promising for potential human application. (Circulation 1990;81:312-318 tages over existing devices by relatively easy insertion and fewer associated complications. Methods ProtocolAtrial septal defects were created by foramen ovale dilatation with angioplasty balloon catheters in 20 piglets weighing 7-29 kg. The animals were heavily sedated by an initial dose of 10-20 mg/kg i.v. ketamine (100 mg/ml, Vetalar, Fort Dodge Laboratories, Fort Dodge, Iowa). The experiments were performed under sterile conditions. A femoral vein cutdown was performed under local anesthesia with 2% xylocaine, and the animals were heparinized (100 units/kg). A multipurpose marker catheter (Cordis, Hialeah, Florida) was introduced into the right atrium under fluoroscopy and was used to probe the foramen ovale. The marker catheter was used both for wire exchanges and dimension measurements after angiography. An angioplasty catheter (Olbert) with a balloon diameter of 10-12 mm was introduced over a 0.035 -in. exchange wire into the left atrium, through the foramen ovale. Three dilatations were performed with dilute contrast material for inflation periods up to 30 seconds. The angioplasty catheter was subsequently replaced by a marker angiographic catheter,

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