Department of Medicine

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Browsing Department of Medicine by browse.metadata.advisor "Coetzee, Andre"

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    Evaluating a bioprosthetic anterior mitral valve leaflet made from autologous jugular vein and expanded polytetrafluoroethylene (Gore-Tex) chordae in a sheep model
    (Stellenbosch : Stellenbosch University, 2016-03) Janson, Jacques; Coetzee, Andre; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. Cardiology.
    ENGLISH ABSTRACT: The purpose of this study was to evaluate whether an autologous vein graft supported by expanded polytetrafluoroethylene (Gore-Tex) chordae can be used to replace an anterior mitral valve leaflet and whether the vein will be able to withstand the stress and strain of deformation, remain viable in the intracardiac environment and be able to adapt morphologically and grow as a valve leaflet. An autologous jugular vein graft, used as a double layer, supported by Gore-Tex chordae was used to create a functional anterior mitral valve leaflet in 21 sheep. No ring annuloplasty was used to support the annulus. The average cross-clamp time was 99 minutes (76 to 151 min) and the average bypass time was 137 minutes (109 to 188 min). One sheep died intra-operatively. The post-operative echocardiogram demonstrated laminar diastolic flow across the mitral valve with an average opening area of 2.8cm². Fourteen sheep had trace to mild mitral regurgitation (MR), 5 sheep had mild to moderate MR and 1 sheep had moderate to severe MR. The body of the vein leaflet tends to billow during systole which increases stress on the Gore-Tex chordae. Three sheep died 2 to 3 days postoperatively from mitral regurgitation due to Gore-Tex chordae that were too long, causing prolapse in 2 cases and 1 case developed a hematoma between the 2 vein layers. Seven sheep died between 1 and 6 months. Four sheep developed infective endocarditis on the mitral valve. Echocardiography at 6 months showed that the mitral regurgitation (MR) progressed with time in most of the sheep: 3 out of 11 sheep had mild MR, 5 had mild to moderate MR and 3 had moderate to severe MR. The progression of MR was due to lack of secondary chordal support of the vein leaflet and mitral annulus, leading to progressive annular dilatation, decreased leaflet coaptation length and increased tension on the primary Gore-Tex chordae. Durability of the valve should be improved by adding an annuloplasty ring and supporting the leaflet with secondary chordae. The 10 surviving sheep were euthanized between 6 to 10 months. All vein implants were examined histologically. The vein leaflet developed intimal fibroplasia and fibrous proliferation between the 2 vein layers as a response to the increased stress upon the tissue. This caused leaflet thickening, but the vein remained flexible without shortening or contracture. The 6 to 10 month vein implants showed viable endothelium and the underlying vein layers clearly showed viability with myofibroblasts, collagen and elastin. A normal healing pattern was seen at the suture lines and no calcification was seen in the vein leaflet apart from the Gore-Tex sutures. No vein growth was demonstrated. Autologous vein has the potential to be used as a valve leaflet substitute, because it remains viable in the intracardiac position for up to 10 months and is able to withstand the stress and deformation of a valve leaflet. Histologically it showed the ability to heal and to morphologically adapt to the new environment.