ABSTRACT
BACKGROUND: Surgical correction of patent ductus arteriosus (PDA) is relatively safe and effective since it does not remain in the category of open-heart-surgery. Although the surgical practice for PDA is performed in almost all hospitals, they contain the problems of anxiety of patients, remained surgical wounds on patients' chests and complications of surgery and general anesthesia. Recently non-surgical methods for the obstruction of PDA have been developed and some of them including buttoned devices are used now. The success rates of these methods approach to 84%. But the problems of embolization, incomplete closure, hemolysis, stenosis of aorta and left pulmonary artery have been reported. We invented new PDA occluder , using stainless steel wire and polyurethane foam. Therefore we investigated the efficacy of occluding blood flow with the new PDA occluder in the vessels of experimental animals. METHOD: Using 304 stainless steel wire which is self-expandable stent, two star-shaped frames were made, each frame forming cone and facing the other's tip. And in the center of the frames polyurethane foam was inserted. 316L stainless steel wire was used to fix the elements described above and some portion of the wire was extracted outside of the frames, shaping hook or round loop with which the occluder could be pulled out in case of misplacement. To create the similar situation to PDA, we made shunts from artery to vein between carotid arteries and jugular veins with surgical bypass grafts or made shunts of direct artery to vein connections without grafts in 4 dogs and 1 pig. Through 8F sheath, we deployed the occluders into the shunts made of 5 grafts or made of 3 arterial ends. Also the occluders were inserted into the femoral artery of dog and iliac artery of pig. After deployment of occluders, angiograms were performed to obscure the efficacy of blocking blood flow and follow-up angiogrms were done in one and two weeks. The animals were sacrificed in one and two weeks to get the tissues including occluders inside. Gross findings were checked about thrombi formation in and around polyurethane foam. RESULTS: The 10 occluders were placed successfully except one site due to misplacement. The occluders successfully blocked the blood flows in all 10 sites within 3 - 60 minutes. Each follow-up angiogram for occluders in one and two weeks revealed good maintenance of blockade in blood flow. Observed gross findings on tissues were packed thrombi formation in the polyurethane foam and membrane formation along the occluder. CONCLUSIONS: This newly developed device revealed good efficacy for occlusion of blood flow including shunts in immediate and follow-up study. Practical method for the delivery of the device and some design modification for proper fitting into the PDA especially for small patients would be required. Longer period of follow-up with more animal experiments for other possible complications including distal embolization would be required also before clinical trial.