This is an intravascular prosthesis deliverable transvenously for the occlusion of large heart defects. The defects are predominantly large atrial septal defects and ventricular septal defects. The device has an occluder connected with a centering counter-occluder. The device is delivered to the heart by known methods. The occluder is released on the distal side of the defect and the proximal centering counter-occluder is stretched, pulling the device over the center of the defect. Subsequently, the centering counter-occluder is buttoned against the occluder and is opposing the right atrial side of the septum. The radiopaque button is placed upon a string to verify buttoning.