Conclusion
Direct comparison of the "total" performance of artificial heart valves is difficult if not impossible. The precise definition of criteria used to benchmark valve performance varies from study to study. To study long term performance large numbers of patents and lengthy observations periods are required. During these periods, there may be an evolution in valve materials or design and in the medical treatment of patents with prosthetic heart valves. The age of the patient at implant and the underlying valvular hear disease are extremely important factors in valve choice and longevity as well. A valve designed for the aortic position may be inappropriate for the mitral position. Consequently, it is not possible to categorise a particular valve as the best. All valves currently in use mechanical and bioprosthetic produce relatively large turbulent stresses (that can cause lethal and or sublethal damage to red cells and platelets) and a greater pressure gradients and regurgitant volumes than normal heart valves.
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