Allograft Heart Valves: Current Aspects and Future Applications

Abstract

Human heart valve allografts continue to represent almost perfect substitutes for heart valves. They have optimal hemodynamic characteristics and are highly resistant to infections. The first clinical use of allograft heart valves was as homovitals being transplanted after antibiotic incubation without any preservation. Since 1968, relatively standardized frozen cryopreservation (SFC) has been employed, including storage in vapor-phase liquid nitrogen. Disadvantages, particularly in pediatric patients, are limited availability due to organ scarcity, inability to grow, degeneration, immune response, and long-term failure. However, in contrast to alternative prosthetic or bioprosthetic heart valve replacements, they represent the best pediatric and juvenile replacement options for the pulmonary valve. Application of multiphoton imaging analysis for three-dimensional visualization of elastin and collagen by induction of autofluorescence without chemical fixation, embedding, and staining has revealed partial destruction of elastic and collagenous matrix in SFC valves. As the overall amount of collagen and elastin remains unchanged, the observed destruction is attributed to freezing-induced extracellular matrix damages due to ice crystal formation during SFC. The objective of this review is an assessment of current allograft preservation methods and the potential of novel preservation techniques to avoid ice formation with accompanied better long-term function.

Surgical techniques for aortic valve xenotransplantation

“…Therefore these prostheses fulfil the structural functions of native heart valves, but they cannot fulfil their biological functions, namely adaptive growth, avoiding thrombogenesis, and self-repair. This severely limits the lifespan of the conventional heart valve prostheses in growing children and young adults with contraindications for anticoagulation [ 42 , 43 ]. While glutaraldehyde fixation decreases the antigenicity of bioprosthetic heart valves to avoid immune rejection, it also may underlie several of the pathophysiological features of early structural valve degeneration.…”

The Impact of Heat Treatment on Porcine Heart Valve Leaflets

“…Pulmonary allograft heart valves are the most commonly transplanted allograft heart valve 17 , 27 and rely on an intricate collagen and elastin structure to function properly. These transplants are particularly important in pediatric patients that are still developing.…”

Application of Homograft Valved Conduit in Cardiac Surgery

“…This preservation method not only retains the biological activity of the valved conduit, but also retains a certain degree of antigenicity. Most patients implanted with valved conduit have humoral immunity against human leukocyte antigen (HLA) ( 25 ). It has been found that donor-derived dendritic cells and endothelial cells expressing HLA-II molecules in valved conduits can directly present antigens and activate receptor immunity ( 26 , 27 ).…”