Heart valve bioprosthesis durability: a challenge to the new generation of porcine valves.

Abstract

Long-term experience with first generation porcine valve xenografts enabled identification of the major limitations to their durability: (1) prosthetic-ventricular mismatch due to the high profile of the stent in patients with mitral stenosis and a small left ventricle; (2) high-pressure fixation with loss of natural collagen crimping in the fibrosa, and wash-out of proteoglycans in the spongiosa; (3) xenograft tissue autolysis, due to the long interval between animal slaughter and aortic valve removal fixation; (4) muscle shelf in the right coronary cusp, which created a gradient and could undergo accelerated calcification and/or spontaneous perforation with time; (5) a flexible polypropylene stent, which could creep or even fracture with consequent inward bending of the stent; (6) progressive time-related dystrophic calcification; (7) host fibrous tissue ingrowth. An awareness of these limitations stimulated technical modifications, which frequently brought about distinct improvements: (1) the reduction of the stent profile eliminated the problem of mismatch, but resulted in a higher tendency towards cusp prolapse and earlier commissural tearing; (2) natural collagen waviness, proteoglycans and cusp extensibility were preserved by employing low or even zero pressure during the fixation process; (3) earlier valve fixation enabled preservation of cell integrity; (4) a new orifice for small valves was designed by replacing the right muscular cusp, thus achieving less gradient and avoiding muscle-shelf-related complications; (5) polypropylene was replaced by Delrin as stent material; (6) calcium-retarding agents like T6 and toluidine blue were applied during commercial processing and storage in order to mitigate tissue mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: M Valente, M Minarini, A F Maizza, U Bortolotti, G Thiene
• Journal: European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery (Eur J Cardiothorac Surg) Vol. 6 Suppl 1 Pg. S82-90 ( 1992) ISSN: 1010-7940 [Print] Germany
• PMID: 1389286 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Review)

Topics

• Bioprosthesis (classification, standards, trends)
• Calcinosis (epidemiology, etiology)
• Heart Valve Prosthesis (classification, standards, trends)
• Humans
• Prosthesis Design (standards)
• Prosthesis Failure
• Quality Control
• Stents (standards)
• Tissue Preservation (methods, standards)