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[Structural changes in valve prostheses].

All available prostheses, either mechanical or biological, may undergo structural alterations which are cause of reoperation or death. Some of these complications are common to all valves, whereas some are specific for certain models. Modern mechanical prostheses usually are resistant to structural deterioration, but still thrombogenic thus requiring long-term anticoagulation therapy to avoid thrombotic and thromboembolic episodes, which implies the risk of anticoagulation related hemorrhages. Bioprostheses, on the other hand, present a lower thrombogenicity, however they undergo by definition structural degeneration, especially dystrophic calcification, which is usually cause of reoperation within 8-10 years from implantation. Other prosthetic complications, such as infective endocarditis and fibrous tissue overgrowth, are common to both types of prostheses.