Despite the wide choice of commercial heart valve prostheses, cryopreserved semilunar allograft heart valves (C-AHV) are required, and successfully transplanted in selected groups of patients. The expiration limit (EL) criteria have not been defined yet. Most Tissue Establishments (TE) use the EL of 5 years. From physiological, functional, and surgical point of view, the morphology and mechanical properties of aortic and pulmonary roots represent basic features limiting the EL of C-AHV. The aim of this work was to review methods of AHV tissue structural analysis and mechanical testing from the perspective of suitability for EL validation studies. Microscopic structure analysis of great arterial wall and semilunar leaflets tissue should clearly demonstrate cells as well as the extracellular matrix components by highly reproducible and specific histological staining procedures. Quantitative morphometry using stereological grids has proved to be effective, as the exact statistics was feasible. From mechanical testing methods, tensile test was the most suitable. Young's moduli of elasticity, ultimate stress and strain were shown to represent most important AHV tissue mechanical characteristics, suitable for exact statistical analysis. C-AHV are prepared by many different protocols, so as each TE has to work out own EL for C-AHV.

Department of Histology and Embryology Biomedical Centre Faculty of Medicine in Pilsen Charles University Prague Karlovarská 48 301 66 Pilsen Czech Republic

Department of Transplantation and Tissue Banking Czech National Allograft Heart Valve Bank Department of Cardiovascular Surgery Motol University Hospital and 2nd Faculty of Medicine Charles University Prague 5 Úvalu 84 150 06 Prague Czech Republic

European Homograft Bank Saint Jean Clinic Rue du Meridien 100 1210 Brussels Belgium

NTIS New Technologies for the Information Society Faculty of Applied Sciences University of West Bohemia Technická 8 Pilsen Czech Republic

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