Candidates for tissue valve (bioprosthetic) replacement
Abstract: Potential candidates for tissue valve (bioprosthetic) replacement are elderly, females planning pregnancy, following infective endocarditis and for right sided valve disease.
Bioprosthetic valves have the advantage of doing away with anticoagulation after the initial period of about 3 months during which the valve gets endothelialized. This is because of their lower thrombogenicity compared to mechanical prosthetic valves which require lifelong anticoagulation.
In elderly patients avoiding anticoagulation by implanting bioprosthetic valves is beneficial because they are more prone for bleeding complications with anticoagulation. Moreover they are more prone for thrombotic episodes with mechanical prostheses because of relatively slower velocity of blood flow. For the same reason, the hemodynamic trauma on bioprosthetic valves is lower in the elderly which reduces the chance of degeneration of bioprosthetic valves in this population. The available functional duration of bioprosthetic of valves also match better with the potential lifespan of the elderly. For all these reasons, bioprosthetic valves are preferred to mechanical prosthetic valves in the elderly population.
Females planning pregnancy
Females planning pregnancy are another group of individuals who can be considered for bioprosthetic valve implantation despite the fact they are young. A mechanical prosthetic valve in this group would mean pre-conception initiation of heparin / low molecular weight therapy to prevent warfarin embryopathy related to oral anticoagulants. The long period of heparin with attendant costs, discomfort, potential injection site issues and lesser effectiveness of heparin compared to warfarin in preventing thrombosis of prosthetic valves are all problems to be considered in this perspective. Long term heparin therapy also carries a risk of osteoporosis. All these problems can be avoided by using bioprosthetic valves in females planning pregnancy. But they should be counseled for the potential need for a repeat surgery after completing the family as they have a chance of needing the same due to the longer projected further lifespan compared to the situation in elderly individuals. Moreover degeneration of bioprosthetic valves is also faster in this younger population with more hyperdynamic circulation compared to the elderly.
Following infective endocarditis
Prosthetic valve endocarditis is a dreaded condition which is very difficult to treat. Those who have had an episode of endocarditis either in the native valve or a prosthetic valve have a higher chance of another episode of endocarditis. Hence it would be preferable to have a bioprosthetic valve which is considered to be more resistant to endocarditis than a mechanical prosthetic valve.
Right sided valve diseases
Right sided valves have a larger valve area and face a lower hemodynamic load. Hence they are also more prone for thrombotic episodes. Bioprosthetic valves have an advantage in this situation due to the lower thrombogenicity. Due to the lower hemodynamic load, the longevity of the bioprosthetic valves are better in right sided locations due to lower tissue degeneration.