Prosthetic heart valves: catering for the few.
Prosthetic heart valves epitomize both the triumphant advance of cardiac surgery in its early days and its stagnation into a retrospective, exclusive first world discipline of late. Fifty-two years after the first diseased heart valve was replaced in a patient, prostheses largely represent the concepts of the 1960s with many of their design-inherent complications. While the sophisticated medical systems of the developed world may be able to cope with sub-optimal replacements, these valves are poorly suited to the developing world (where the overwhelming majority of potential valve recipients reside), due to differences in age profiles and socio-economic circumstances. Therefore, it is the latter group which suffered most from the sluggish pace of developments. While it previously took less than 7 years for mechanical heart valves to develop from the first commercially available ball-in-cage valve to the tilting pyrolytic-carbon disc valve, and another 10 years to arrive at the all-carbon bi-leaflet design, only small incremental improvements have been achieved since 1977. Similarly, bioprosthetic valves saw their last major break-through development in the late 1960s when formalin fixation was replaced by glutaraldehyde cross linking. Since then, poorly understood so-called 'anti-calcification' treatments were added and the homograft concept rediscovered under the catch-phrase 'stentless'. Still, tissue valves continue to degenerate fast in younger patients, making them unsuitable for developing countries. Yet, catheter-delivered prostheses almost exclusively use bioprosthetic tissue, thereby reducing one of the most promising developments for patients of the developing world into a fringe product for the few first world recipients. With tissue-engineered valves aiming at the narrow niche of congenital malformations and synthetic flexible leaflet valves being in their fifth decade of low-key development, heart valve prostheses seem to be destined to remain an unsatisfying and exclusive first world solution for a long time to come.
Zilla
Peter
P
Christian Barnard Department of Cardiothoracic Surgery, University of Cape Town Medical School and Groote Schuur Hospital, Anzio Road, 7925 Observatory, Cape Town, South Africa. peter.zilla@uct.ac.za <peter.zilla@uct.ac.za>
Brink
Johan
J
Human
Paul
P
Bezuidenhout
Deon
D
D000818:Animals; D000941:Antigens / Q000276:immunology; D002404:Catheterization; D006350:Heart Valve Prosthesis; D006351:Heart Valves / Q000276:immunology / Q000502:physiology / Q000601:surgery; D006801:Humans; D013923:Thromboembolism / Q000473:pathology; D023822:Tissue Engineering
D000941:Antigens