The majority of ventricular septal defects (VSDs) are perimembranous, accounting for 75-80% of all VSDs. The objective of this study was to investigate occluder selection and transcatheter closure technique for multi-hole perimembranous VSD with aneurysm, and to evaluate clinical efficacy and safety. Patients with multi-hole VSDs and aneurysm (n = 64) were selected for the procedure using transthoracic echocardiography. Double-disc symmetrical, small-waist double-disc asymmetrical and zero eccentricity occluders were selected based on left ventricular angiography. The closure was successful in 63 of 64 patients (98%). The double-disc symmetrical occluder was used in 16 cases, the small-waist double-disc asymmetrical occluder in 42 cases, and the zero eccentricity occluder in 8 cases (2 occluder types were used in 2 cases). Fifteen minutes after the procedure, 52 cases had no residual shunt and 12 had a trace amount of residual shunt. The residual shunt disappeared in five cases 5-7 days post procedure, with a trace amount of shunt remaining in seven cases. Transient conduction abnormalities related to the procedure occurred in six patients; however, none required permanent pacemaker implantation. At the 1-month, 6-month, 1-year, 2-year, and 3-year follow-up visits, echocardiography indicated that the position of the occluders was fixed, and there were no complications including residual shunt, newly developed atrioventricular block, thromboembolism, or bacterial endocarditis. The study results indicate that left ventricular angiography is useful in selecting the most appropriate device for transcatheter closure of multi-hole perimembranous VSD with aneurysm. The transcatheter closure procedure is safe and effective with little residual shunt and no major complications for up to 3 years of follow-up.

The aging behavior and degradation mechanism of nitrile rubber (NBR) under free and compression states were investigated in simulated air and hydraulic oil environments at various elevated temperatures. The variations in the crosslinking density, volatile components and the chemical structure of NBR during aging were studied using equilibrium swelling testing and dynamic mechanical analysis (DMA), pyrolysis-gas chromatography-mass spectrometry and attenuated total reflection-Fourier transform infrared spectroscopy. The migration of additives in different media and the crosslinking density of NBR aged in different conditions were compared. The tensile strength, DMA, and thermogravimetric analysis results were consistent with the changes in the crosslinking density of NBR and the migration of additives. Four effects of the simulated hydraulic system on the thermal aging of NBR were examined. Both the compression stress and the oil medium slowed the aging of NBR. The results can provide new insights into the use of NBR products in lubricating oil environments and NBR lifespan prediction in hydraulic working conditions.