Microstructural alterations owing to handling of bovine pericardium to manufacture bioprosthetic heart valves: A potential risk for cusp dehiscence

Cross-linking and anti-calcification of prosthetic heart valves have been continuously improved to prevent degeneration and calcification. However, non-calcific structural deteriorations such as cuspal dehiscences along the stent still require further analysis. Based upon the previous analysis of an explanted valve after 7 years, a fresh commercial aortic valve was embedded in poly(methyl methacrylate) (PMMA) and cut into slices to ensure the detailed observation of the assembly and material structures. A pericardial patch embossed to provide the adequate shape of the cusps was investigated after paraffin embedding and appropriate staining. The microstructural damages that occurred during manufacturing process were identified and evaluated by light microscopy, polarized microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The wavy collagen bundles, the key structure of the pericardium patch, were damaged to a great extent at suture sites along the stent and in the compressed areas around the stent post. The fixation of the embossed pericardium patch along the plots of the stent aggravated the microstructural modifications. The damages mainly appeared as the elimination of collagen bundle waviness and delamination between the bundles. Considering the modes of failure of the explant, the damages to the collagen bundles may identify the vulnerable sites that play an important role in the cusp dehiscence of heart valve implants. Such information is important to the manufacturers. Recommendations to prevent in vivo cusp dehiscence can therefore be formulated. Les méthodes de réticulation et de traitement anticalcique des valves cardiaques prothétiques se sont constamment améliorées concernant la prévention de la dégénérescence et de la calcification des tissus. Toutefois, les détériorations structurales en absence de calcification telles que les déchirures des cuspides le long de l’armature, requièrent des études supplémentaires. Suite à l’analyse antérieure d’une valve explantée 7 années après sa mise en place, une valve commerciale fraîchement fabriquée fut enrobée dans le polyméthylméthacrylate (PMMA) et coupée en lames fines afin d’observer les structures et les matériaux assemblés. Un feuillet de péricarde après embossage pour former les cuspides fut également étudié après enrobage dans la paraffine et colorations multiples. Les modifications microstructurales qui sont survenues pendant la fabrication des valves furent