Device and delivery system
The closure device and delivery system used in this study was a domestic concentric occluder (Shanghai Shape Memory Alloy Co., Ltd., Shanghai, China, and Shanghai Push Medical Device Technology Co., Ltd., Shanghai, China). The minimum size of the occluder was 4 mm. Both disks of the concentric occluder have a diameter of 2 mm larger than that of the waist (Fig. 1). The waist is 3.5-4.5 mm in height. The entire delivery system consisted of a trocar, a guidewire, a delivery cable, a short loading sheath, a long delivery sheath and a dilator.
Before using, the selected concentric occluder must be immersed in heparin saline, and the delivery system must be washed with heparin saline. The selected occluder was screwed onto the delivery cable which had been inserted into the loading sheath. Then, the procedure of smooth release and withdrawn of the device must be examined prior to the surgery via the device being pushed forward out the sheath and pulled back into the sheath. In order to improve the safety of this closure technique, a device protective suture of 3–0 polypropylene was passed through the mesh of the right disk near the middle of every device. It has to be emphasized that the suture cannot entwine the delivery cable as it was pulled out of the sheath.