Abstract 14470: Acquired Hemocompatibility of Bioprosthetic Heart Valve Results From Fibrin Deposition and Endothelial Covering in Human

IntroductionBioprosthetic heart valves (BV) are made of xenogeneic pericardium treated with glutaraldehyde in aortic valve replacement (AVR). The main reason to opt for BV is avoiding indication of lifelong anticoagulation, enabled by their low thrombogenicity risk. To explain this low thrombogenicity, an acquired hemocompatibility process was hypothesized but never extensively studied because of the impossibility to access undegenerated material.HypothesisThe objective was to explore and understand mechanism of acquired hemocompatibility. Thus, undegenerated BV from 9 different patients implanted with a Carmat bioprosthetic total artificial heart (C-TAH) were studied for the first time.MethodsFour BV for each patient with duration from 45 to 304 days were studied. We performed routine histopathology and immunophenotypic characterization of explanted BV along with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to explore the biological deposit.ResultsIn short implantation duration time, HE histological sections showed a fibrin deposit with inflammatory cells embedded and superficial infiltration of cells, persisting in long duration but not damaging integrity of the pericardium. In SEM, this fibrin deposit is organized in a compacted smooth fibrin network in longer implantation durations. Pseudotubes formation is observed in short durations, and endothelial cells (EC) monolayer covering was observed on this fibrin cap at longer implant durations. In toluidine blue semi-fine sections, we observed flat nucleus cells while tight junctions between these cells with basal lamina were observed in TEM. This endothelial cells covering is positive for specific endothelial marker VE-Cadherin in confocal analysis. The percentage of the BV surface with EC covering is significantly increasing from day 45 to 304 days.ConclusionsIn conclusion, healthy BV implanted with C-TAH enabled us to study for the first time undegenerated implanted valve in human. Biomaterial passivation by an organized fibrin deposit and formation of EC monolayer on top of its surface achieve an optimal hemocompatibility without any modification of pericardial tissue.