Hydrodynamics of Cardiac Valve Prostheses: Is Excellence Necessary?
Few papers have compared the hydrodynamic features of various cardiac valve prostheses with respect to surgical results. All prostheses offer resistence to blood flow and most exhibit regurgitation, but we have come to expect improvements in symptoms and survival despite widely varying hydraulic performance. When patients do not achieve the full benefits of surgery or exhibit late deterioration despite an apparently normally functioning prosthesis, we begin to suspect that the imperfections of valve substitutes are playing a role in patient outcome. Objective data, such as analysis of symptoms or sequential late studies of cardiac function, especially after 10 years, would be useful. Unfortunately, almost all surgical survivors improve postoperatively and those who deteriorate functionally die and are unavailable for late analysis. The majority of late deaths are due to congestive heart failure. Not all of these deaths can be blamed on the late timing of surgery or inadequate myocardial protection during the procedure. For these reasons and because most valve prosthesis recipients have other underlying cardiac problems, it is important to evaluate the specific impact of long-term prosthetic hydraulic performance. Contributing to poor valve performance are 1) prosthesis-patient mismatch and 2) substantial valve area reduction, resulting in significant increases in transvalvulargradients. Most hemodynamic studies demonstrating improvement are reported at rest, yet many patients exhibit marked elevations of pulmonary artery pressure and transvalvular pressure gradients when exercising. Our own assessment of two groups of patients suggests that significant improvement in New York Heart Association (NYHA) Classification is possible with a hydraulically superior valve substitute, even in a moderate follow-up period. It is our obligation to demonstrate that new valve substitutes serve their recipients as well in the second, and even third, decade after implantation as they do in the first.
KeywordsValve Replacement Mitral Valve Replacement Valve Prosthesis Effective Orifice Area Aortic Valve Area
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