Introduction: Surgical aortic valve (AV) replacement is performed to treat AV stenosis or insufficiency. Biological prostheses implanted are mostly fabricated from bovine pericardium. Due to prostheses deterioration Re-operation of patients is required 10-15 years after implantation. Alternative strategies use autologous pericardium after glutaraldehyde (GA) fixation e.g. in the Ozaki-procedure. Advantages are expected regarding immune response, biomechanics and treatment expenses. In the presented study, quality properties of residual pericardia after autologous AV replacement adjacent to the extracted valve cusps were experimentally analyzed and compared with bovine pericardium from clinical patch or prosthesis material. Initially, parameters such as tissue thickness, collagen- glycosaminoglycan- and elastin content and vessel density in patient pericardium tissue were quantified.

Hypothesis: Residual autologous pericardium after AV replacement exhibits different and more heterogeneous extracellular matrix (ECM) and vessel structure compared to bovine pericardium.

Material and methods: Human pericardia (n=7) were GA-fixed and used to extract aortic valve leaflets in the theatre. According to patients informed consents (EK247052019) residual material was used to analyze tissue thickness with the thickness gauge FD50. If possible in each pericardium histological sampling was performed at three positions of each leaflet (commissure and left or right side of sutured cusps). Three to ten samples per pericardium were examined. Picrosirius red-, HE- and alcianblue- and adapted elastica van giesson staining were performed with standard protocols, digitalized (slide scanner) and quantified via Fiji software (color deconvolution plugin; user threshold values). Two commercially available glutaraldehyde-treated pericardial patches (Edwards; Supple Peri-Guard; Trifecta bioprosthesis were equivalently analyzed.

Results: Human pericardia were with 348.8 ± 52.9 µm significantly thinner than bovine pericardia (524.4 ± 96.8 µm). Histological evaluation of up to ten specimen per individual human pericardium revealed heterogeneity in ECM bundles, vessel density and remaining connective tissue. The number of vessels per area of tissue section was in all individual human pericardia significantly higher (32.6 ± 4.4 mm^-2 to 27.4 ± 5.5 mm^-2) compared to patch materials (5.1 ± 2.3 mm^-2). ECM component collagen (picrosirius red) was quantified as rate of specimen area. Human pericardia exhibit with values from 60.1 ± 1.0 % to 70.9 ± 6.4 % a significant lower collagen content compared to patch pericardia (86.8 ± 2.4 %). High standard deviations of human pericardial analyses and significant differences also between two patient samples already indicate a high heterogeneity. In addition, content of elastic fibres (elastica van giesson, adapted) in human pericardium is significantly lower than in bovine patch tissue but rate of glycosaminoglycans (alcianblue) did not differ.

Conclusion: Autologous pericardia implanted in AV position are significantly thinner than bovine pericardial patch material and exhibit a higher vessel density. A significant lower rate of collagen and elastin in histological sections was detected in human compared to bovine pericardia. Intra-individual differences in autologous tissues are ongoing focussed by the definition of the individual tissue heterogeneity in comparison to bovine pericardia prepared according to Ozaki-procedure.