Modified chordal sparing mitral valve replacement as effective technique for both stenotic and insufficient mitral valves.

BACKGROUND: Chordal apparatus preservation is important for preserving left ventricular (LV) function in the long-term perspective. We present results of originally modified chordal-sparing mitral valve replacement (MVR) successfully used in patients with mitral stenosis and mitral insufficiency. METHODS: The modified surgical method involves preserving only four strut chords with portions of the mitral valve leaflets, which are later fixed to the fibrous ring. The rest of the leaflets and marginal chords are removed. RESULTS: Starting from 1998, 484 modified universal chordal-sparing MVR were performed including 270 (55.79%) in patients with rheumatic mitral stenosis and 214 (44.21%) in patients with mitral valve insufficiency. Overall, 116 patients underwent isolated MVR, and 368 patients underwent MRV with concomitant surgical procedures. The overall in-hospital mortality was 2.5% (12 patients). Long-term efficiency was assessed in patients discharged after isolated MVR (114 patients), average follow-up period was 3.1±0.6 years. Preservation of strut chords ensured normalization of intraventricular anatomy and prevented LV dilatation; the LV Sphericity Index is maintained at 0.44-0.63. Heart failure functional class (NYHA) was improved in all patients. Non-fatal prosthesis-related complications were observed in 11 patients (9.65%). Three patients (2.63%) died due to extracardiac causes. CONCLUSIONS: The proposed modification of the strut chordal-sparing mitral valve replacement technique allows preserving functionally complete annulo-papillary apparatus, regardless of the nature of valvular dysfunction, and provides parallel movement to the mechanical prosthesis. This modified surgical technique is safe and effective and eliminates the risk of jamming of the prosthesis disk and left ventricular outflow tract obstruction.

Electronic and chemical properties of nanostructured cerium dioxide doped with praseodymium.

Nanostructured doped ceria is a prospective material for catalytic applications such as the construction of membranes with mixed electronic and ionic conductivity for effective syngas production. In this article, the surface properties of nanostructured ceria doped with praseodymium have been studied by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy of adsorbed carbon monoxide. The effects of supporting 1.4 wt % Pt as well as structural changes upon the reduction of the samples with methane have been investigated. While in samples without supported platinum, mainly praseodymium cations are reduced in a methane atmosphere; stronger reduction of cerium cations was found in the case of surface modification with Pt. The structural differences correlate with results from temperature-programmed reaction experiments with methane. Explanations are discussed in terms of different reaction mechanisms.