BACKGROUND: It is difficult to cover aneurysm-like ventricular septal defect (VSD) of large inlet and multiple outlets completely with symmetrical type occluders or eccentric type occluders. OBJECTIVE: To investigate the feasibility of A4B2 occluder devices for covering aneurysm-like VSD, and to observe the effects of proper occhiders selected according to pseudoaneurysm size on coveting aneurysm-like VSD. DESIGN: Case analysis.SETTING: the First Hospital of Hebei Medical University. PARTICIPANTS: From August 2004 to May 2006, 226 patients with the pseudoaneurysm of petimembranous VSD, who underwent interventional therapy in the First Hospital of Hehei Medical University, were recruited in the study. According to the results of the left ventricular angiography, 36 patients of pseudoaneurysm of petimembranous VSD with large inlet and multiple outlets were closured with A4B2 occluder devices. According to the results of the left ventricular angiography, the mean diameter of the left inlet of VSD was (10.6+8.7) mm (ranged from 8 to 21 mm), the mean diameter of the right outlet of VSD was (3.1 ± 2.9) mm (ranged from 2 to 8 ram). Main materials: Occluder device and delivery mechanism were offered by Shanghai Shape Memory Alloy Materials Company and Beijing Starway Medical Technology Inc. They were processed into double disks using nickel-titanium shape memory alloy wires by a special technology to close VSD by a transcatheter approach. The size of the occluder was denoted with the diameter of the waist, and the Size ranged from 4 to 16 mm in the present study. METHODS: All the occluders were transferred by a 7-10 F transferring sheath from right heart system, and the mean diameter of the occluders was (6.364-2.48) nun (ranged from 4 to 16 ram). Fifteen minutes after the procedure, left ventricular angiography and transthoracic echocardiography (TIE) were performed again to evaluate the efficacy. After the procedure, electrocardiogram (ECG) monitoring lasted for 5 successive days in all patients, and ECG and TIE were performed 1, 3, 6 and 12 months later. MAIN OUTCOME MEASURES: Residual shunt, arrhythmia and valve function as well as blood compatibility. RESULTS: Sixteen cases were closured by placing the occhiders into left inlet of VSD, 16 cases were closured by placing the occluders into the pseudoaneurysm completely, and 4 cases were closured at the outlet of the defects. The results of the left ventricular angiography and TTE that performed fifteen minutes after the procedure demonstrated that 32 cases were completely closured and slightly residual shunts (< 3 mm) was found in other 4 patients. And confirmed by TIE, the residual shunts completely disappeared in 2 of the 3 patients 24 hours later while in the other one in 1 month after the procedure. Temporary left bundle branch block was found in 3 cases while temporary right bundle branch block was found in 2 cases, and all of them recovered within one week. Without severe complications, all of the 36 patients were treated successfully with A4B2 (thin waist shape) occluder devices made in China. Critical appraisal in blood compatibility of the implantation materials used in this research had been performed. The hemolysis ratio was less than 5%, the platelet adhesion was less, and the blood coagulation function ,the immune system response( immunoglobulin and complement)and the re-endothelialization of material surface were all normal. CONCLUSION: Transcatheter interventional therapy with domestic A4B2 occluder devices for VSD with pseudoaneurysm is safe, effective, promising, and has fewer complications. The key to the procedure is to select suitable occluders and suitable positions where to plant them according to the size, morphologic characteristics, position, and maturity of the pseudoaneurysm.