Long-Term Clinical Evaluation of Mitral Valve Replacement with Porcine Bioprosthetic Valves in Dogs

Abstract

ABSTRACT. This study evaluated the long-term clinical performance of newly developed porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound for mitral valve replacement (MVR) in dogs. Five beagle dogs underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass. Antithrombotic drugs were administered only for one month after MVR. Six months after MVR, transvalvular regurgitation was not observed in all dogs, paravalvular leakage was seen only in one dog. Twelve months after MVR, mild transvalvular regurgitations were observed in two dogs. Although diastolic atrioventricular pressure gradient was increased gradually, no significant differences were observed. Pressure half-time and valve area were within normal ranges as the bioprosthetic value. There was no clinical symptom of the thrombosis and the thrombogenesis was not observed in the porcine bioprosthetic valve and the annulus in all dogs for twelve months after MVR. The clinical findings suggest that antithrombogenicity of the valves were maintained, though the duability might not be enough in the long-term period. Mitral regurgitation (MR) is the most common acquired heart disease that increases with aging in dogs. MR is caused by myxomatous degeneration with disorganized collagen fibers in the mitral valve and increased content of acid mucopolysaccharide. In myxomatous degeneration, the valves are thickened and the valve leaflets become redundant; secondary dilation of the valve annulus contributes to MR. Progressive congestive heart failure and death are the inevitable consequences of severe MR despite any optimal medical treatment [13,19].Surgical treatment for MR has not been established in veterinary medicine, although radical operation is generally performed in human medicine. Mitral valve replacement (MVR) is one of the surgical treatments for MR, and bioprosthetic valves are recommended for dogs, because of their antithrombogenic property [24]. In human medicine, the xenograft valve is a mainstream of the bioprosthetic valve. There are different types of xenograft bioprosthetic valves that are routinely cross-linked during manufacturing using glutaraldehyde because of the antigenicity and sterility [4,8]. Bioprosthetic valves have a possibility of prosthetic valve failure due to calcification, pannus formation and tissue degeneration; several reagents have been extensively investigated to inhibit them [5,6,18]. Polyepoxy compound (Denacol EX-313) was developed in order to reduce calcification, degeneration and thrombosis [17,22].In a previous study, the porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compounds were newly developed for MVR. MVR procedures under cardiopulmonary bypass (CPB) and the use of the newly developed porcine bioprosthetic valves were shown to have been effective in dogs during short-term evaluation [21]. The aim of this study was to evaluate the long-term clinical performance of newly developed porcine bioprosthetic valves for mitral valve replacem...

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