Is distortion of the bioprosthesis ring a risk factor for early calcification ?

<p>Abstract</p> <p>Background</p> <p>As the population ages, bioprosthesis are increasingly being used in cardiac valve replacement. Pericardial bioprosthesis combine an excellent hemodynamic performance with low thrombogenicity, but valve failure associated with calcification remains a concern with these valves. We describe distortion of the bioprosthesis ring as a risk factor for early calcification.</p> <p>Methods</p> <p>A total of 510 patients over the age of 70 years underwent isolated aortic valve replacement with the Mitroflow (A12) pericardial bioprosthesis. Thirty two patients (6,2%) have undergone a second aortic valve replacement due to structural valve dysfunction resulting from valve calcification. In all patients a chest radiography and coronary angiography was performed before reoperation. A 64 Multidetector Computed Tomography (MDCT) with retrospective ECG gating study was performed in four patients to evaluate the aortic bioprosthesis.</p> <p>Results</p> <p>Chest radiography showed in all patients an irregular bioprosthesis ring. At preoperative coronary angiography a distorted bioprosthesis ring was detected in all patients. Macroscopic findings of the explanted bioprostheses included extensive calcification in all specimens.</p> <p>Conclusion</p> <p>There was a possible relationship between early bioprosthetic calcification and radiologic distortion of the bioprosthesis ring.</p

Effect of ventricle motion on the dynamic behaviour of chorded mitral valves

An Immersed Boundary (IB) model is employed to investigate the dynamic behaviour of a novel chorded mitral prosthesis, which is in the early stages of its development, under physiological flow conditions. In vivo magnetic resonance images (MRIs) of the left ventricle are analysed to determine the relative motion of the mitral annulus and the papillary muscle regions of the ventricle. The dynamic boundary conditions are incorporated into IB simulations to test the valve in a more realistic dynamic geometric environment. The IB model has successfully identified the effect of the dynamic boundary conditions on the mechanical behaviour of the valve and revealed the strengths and weaknesses of the current mitral design. The mechanical performance of the prosthesis is compared with recent studies of native porcine valves; differences in mechanical behaviour are observed. Potential improvements for the design of the prosthesis are proposed. © 2007 Elsevier Ltd. All rights reserved

Effects of ventricle motion on chorded mitral prostheses

We assess the dynamic performance of a novel chorded mitral prosthesis based on the physiology of the human mitral valve using an immersed boundary code. In order to analyse the effect of the ventricle motion on the chorded valve in dynamic opening, in vivo MRI data is used to determine the relative motion of the mitral annulus and the papillary muscles regions of the ventricle. The dynamic fluid-structure interaction model has successfully identified the influences of the ventricle motion on the valve's mechanical behaviour, and revealed the strengths and weaknesses of the current mitral design. Potential improvements for future designs are also discussed. Copyright © 2006 by ASME

Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep

Survival to six months for sheep with a non-biostable polyurethane mitral heart valve prosthesis has been reported previously, however, with surface degradation and accumulation of calcified fibrin/thrombus that impaired leaflet motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prostheses of documented hydrodynamic performance, implanted in the mitral position, were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and electron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving leaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve prostheses. </jats:p

Modelling chorded prosthetic mitral valves using the immersed boundary method.

The Immersed Boundary (IB) Method is an efficient method of modelling fluid structure interactions. However, it has two main limitations: ease of use and ability to model static loading. In this paper, the method is developed, so that it can efficiently and easily model any multileaflet elastic structure. The structure may include chordae, which attach to the leaflets and continue through the leaflet surfaces. In addition, an external surface pressure may be applied to the leaflets, thus enabling the deformations that arise under steady loads to be solved. This method is validated for a model of the native mitral valve under systolic loading and for a prosthetic aortic valve under static loading. It is then applied to a new chorded prosthetic mitral valve, housed in a cylindrical tube, subject to a physiological periodic fluid flow. Results are compared with those obtained by using the commercial package ANSYS as well as with experimental measurements. Qualitative agreements are obtained. There are some discrepancies due to the current IB method being unable to model bending and shear behaviour. In particular, the fibre structures of the new prosthetic valve model developed using the IB method may be prone to crimping. Further development of the IB method is necessary to include bending effects. This will improve the accuracy of both the dynamic and static analysis