The analysis of oauses of bioprosthetio valve dysfunction: the example of «UniLine» bioprosthesis

Aim: to assess the contribution of primary tissue failure, calcification, bacterial contamination and pannus to bioprosthetic valve dysfunction.Materials and methods. To evaluate degenerative changes of the «UniLine» bioprosthesis explanted from the mitral position with macroscopic examination, light and scanning electron microscopy, and micro-computed tomography (micro-CT). Light microscopy was used to analyze cell composition, the presence of bacteria, the localization of calcific deposits and recipient cells. Scanning electron microscopy allowed confirming the presence of bacteria. Micro-CT was used to evaluate the deformation of the bioprosthetic elements, the distribution of calcific deposits and their volume in the valve tissue.Results. The presence of pannus, calcification, primary tissue failure and bacterial contamination were found among the causes leading to bioprosthetic dysfunction. Prosthetic leaflets showed pannus growth from the inflow tract. Excessive circumferential pannus extended into outflow tract. Calcific deposits were mostly localized in the commissural zone and the central portion of the leaflets. The total volume of calcification accounted for 1/3 of the bioprosthetic tissue component. The relationship between calcification and stress-strain properties of the bioprosthetic elements has been indicated. The asymmetric deformation of the bioprosthetic stent frame and leaflets with 1.5-fold thickening of the last has been found. The areas with loose and fragmented collagen and elastic fibers contained red blood cells and neutrophils. Endothelial cells and fibroblastic cells were present in the outer surface layers. There were no signs of calcification in the areas accumulating cells and bacteria.Conclusion. We can assume that primary tissue failure, calcification, bacterial contamination and pannus independently contribute to the onset of bioprosthetic heart valve dysfunction.