The repeating dislodgement of an ASO device

Transcatheter closure with an Amplatzer Septal Occluder (ASO) has become the standard treatment for secundum atrial septal defect (ASD). However, this procedure is associated with complications, such as device dislodgement. A 52-year-old woman was admitted with exertional dyspnea. Transesophageal echocardiography showed an ASD involving a 29 mm defect. Calculated Qp/Qs was 5.6 and all the rims were > 5 mm, with the exception of the posterior rim, which was 3 mm. Transcatheter ASD closure with an ASO was performed under general anesthesia. During emergence from anesthesia, tachycardia developed and the ASO device became dislodged. Hemodynamic changes associated with the end of anesthetic administration were believed to have led to device dislodgement. In a second transcatheter ASD closure, a low dose of propofol and remifentanil was maintained during emergence from anesthesia to reduce hemodynamic changes. However, device dislodgement occurred with nonsustained ventricular tachycardia. Finally, surgical ASD closure was performed. The large defect size, high Qp/Qs, and rim deficiency may have predisposed to device dislodgement after transcatheter ASD closure with ASO. The risk of device dislodgement should be considered in advance of surgery and, in high-risk cases, the patient's cardiovascular status should be closely monitored

Observation of micropores in hard-carbon using Xe-129 NMR porosimetry

The existence of micropores and the change of surface structure in pitch-based hard-carbon in xenon atmosphere were demonstrated using Xe-129 NMR. For high-pressure (4.0 MPa) Xe-129 NMR measurements, the hard-carbon samples in Xe gas showed three peaks at 27, 34 and 210 ppm. The last was attributed to the xenon in micropores (<1 nm) in hard-carbon particles. The NMR spectrum of a sample evacuated at 773 K and exposed to 0.1 MPa Xe gas at 773 K for 24 h showed two peaks at 29 and 128 ppm, which were attributed, respectively, to the xenon atoms adsorbed in the large pores (probably mesopores) and micropores of hard-carbon. With increasing annealing time in Xe gas at 773 K, both peaks shifted and merged into one peak at 50 ppm. The diffusion of adsorbed xenon atoms is very slow, probably because the transfer of molecules or atoms among micropores in hard-carbon does not occur readily. Many micropores are isolated from the outer surface. For that reason, xenon atoms are thought to be adsorbed only by micropores near the surface, which are easily accessible from the surrounding space.</p