The influence of glutaraldehyde on the microscopic structure of human pericardium

•This is the first histological and microscopic study which examines the microscopic collagen structure of the human pericardium in relation to glutaraldehyde (GA) concentration and incubation time.•Independent of the GA concentration, with increasing incubation time the collagen fibers became more compact.•Especially for a concentration of 0.625% GA, typically used in cardiac surgery, prolongation of the incubation has an appreciable effect on the structure of the collagen fibers.•These unchangeable modifications in collagen structures are assumed to promote the calcification process that often causes early (and avoidable?) reoperations. In our study, we investigate the collagen structure of human pericardium microscopically in dependence of glutaraldehyde (GA) concentration and fixation time. Pericardial samples were taken from 9 patients aged 40+ years who underwent cardiac surgery, either coronary artery bypass surgery or valve implantation/reconstruction. Specimens were cut in 5 equal pieces and treated with GA at fixed concentrations (0.3125%, 0.625%, or 1.25%) but different exposer times (5 min, 10 min, 20 min, 30 min, and 60 min). Elastica van Gieson (EvG) staining was used for microscopic examination of pericardial collagen structure. The collagen structure studied microscopically depended on both GA incubation time and GA concentration. At low GA concentrations (0.3125%, 0.625%) and short incubation times, individual collagen fibers appeared separately. After one hour incubation period, single collagen fibers could not be distinguished at any GA concentration. For fixed incubation times no differences were seen in the collagen structure when 0.3125% and 0.625% GA were used. However, at a concentration of 1.25% GA fusion of individual collagen fibers was already observed at low incubation times. Pericardial collagen structure changes with increasing incubation time and increasing GA concentration by raising fusion of single fibers. For GA concentrations of ≤0.625%, fiber fusion depends plainly on incubation time. That is relevant as this concentration is used in cardiac surgery. At a concentration of 1.25% GA, single collagen fibers could not be separated, even at short incubation times. Fusion of individual collagen fibers and changes in appearance (less undulating) were assumed to be responsible for stiffening of GA-fixed pericardium.