Cardiovascular Prosthetic Surgery: An Analysis of Cellular and Molecular Patterns Underlying Valve Implantation Failure

Cardiac valves have a very complex microscopic architecture, this is due to the presence of many cell types and to the variegated stroma. From a morphological point of view, both physiological and pathological processes clearly show there to be an anatomic continuity between valve leaflets and perivalvular tissues; indeed, both component should be taken into consideration during thrombotic processes and in fibrous tissue formation. At present, morphological features are well known and classified, while little is known about histogenetic features: fibrous tissue formation and the role of the various types of adhesion molecules and cells which participate in this process still have to be fully elucidated. In the current study, we focused on the histological analysis of the pannus. In particular, we demonstrated that the true connective nature of the exuberant fibrous tissue was entirely composed of collagen/fibronectin fibre bundles and fibroblasts. Moreover we observed that the phlogistic infiltrates were composed of immune cells, mainly represented by CD4 + and CD8 + T lymphocytes. Finally we also tried to assess not only the degree of endothelial layer loss, but also the extent of revascularization in the exuberant fibrous tissue. Cardiac valves have a very complex microscopic architecture due to the presence of many types of cells, as well as to the variable stromal pattern, involving intercellular matrix and bioactive molecules. From a morphological point of view, both physiological and pathological processes clearly demonstrate an anatomic continuity between valve leaflets and perivalvular tissues; this anatomical feature is common to mechanical and biological prosthetic valves and leads to an involvement of both valves and perivalvular tissues in thrombotic processes and in fibrous tissue formation. Thrombotic and fibrotic outcomes are similar in use of the two prosthetic types, although a more frequent and early risk of thrombosis has been reported in cases where mechanical valves were employed (1-4).