A new shape-memory coil for transcatheter closure of the PDA was developed and evaluated in a dog PDA model. The coil is sensitive to temperature (composed of thermal shape-memory nickel-titanium). The coil was delivered to and implanted in the PDA model with a 5F catheter through the femoral artery. The PDA model was made in 14 dogs by infrarenal aorta banding (diameter 2.0 +/- 0.6 mm; length 2.9 +/- 0.1 mm). Coils were implanted in 10 dogs, whereas the other 4 dogs served as controls. Complete occlusion of the PDA model was confirmed by angiography 24 hours after the coil implantation in 7 of 10 dogs, whereas small residual flow was noted even 2 weeks after the coil implantation in the other 3 dogs. The PDA model internal diameter in the dogs with complete occlusion (1.8 +/- 0.2 mm) was significantly smaller than the diameter in dogs with residual flow (2.9 +/- 0.4 mm, P < 0.05). In the 4 control dogs, the PDA model remained patent 2 weeks after the banding. We conclude that the transcatheter occlusion with the shape-memory coil was effective in the small-diameter PDA model.