Bioprosthetic valve durability: the proof is in the pudding.

Dystrophic calcification is the Achilles heel of biomaterial durability. Conventional fixation of collagen-rich biomaterial is performed with glutaraldehyde, which cross-links proteins to provide material stability and reduce xenograft antigenicity. Glutaraldehyde, however, is cytotoxic and is associated with a postfixation tissue environment that predisposes to calcification. Devitalized cells release calcium into the interstitial compartment of the tissue that binds to free aldehyde groups and exposed acidic phospholipids, contributing to stiffening and ultimate failure of physiologic function. Although controversial, residual antigenicity is also thought to play a role in glutaraldehyde-fixed biomaterial degeneration. Commercial valve companies seek ways to improve bioprosthetic valve durability by reducing long-term uptake of calcium. Anticalcification strategies have resulted in improved valve durability when compared with tissue fixation alone. Anticalcification strategies most commonly entail treatment with detergents to remove calcium-binding phospholipids or treatment with compounds that alter the structure of exposed aldehyde groups. Because the calcification process is thought to be multifactorial, combining different treatment modalities to develop synergy in an anticalcification strategy is proposed to extend the life of component biomaterials. Flameng and colleagues present an industry-financed study of a new proprietary tissue preservation technology that tests a synergistic anticalcification strategy in an ovine model of bovine pericardial mitral valve replacement. The test valves are compared with commercially available valves treated with phospholipid depletion alone (Edwards 6900P, XenologiX; Edwards Lifesciences, Irvine, Calif). The novel treatment also uses this same method of phospholipid and cell debris removal, a solution of ethanol and surfactant. The new technology introduces specific methodology to remove free aldehyde groups, although the procedure is not described. It is unknown if this represents the same