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The effects on the blood of prostheses implanted in the heart or blood vessels are discussed. Particular attention is paid to red cell damage. Intracardiac prosthetic devices may be associated with hemolytic anemia which is characterized by red cell fragmentation and intravascular hemolysis. Red cell destruction probably results from the mechanical effects of altered circulatory dynamics in which abnormal velocity and turbulence of flow are generated.
In vitro systems have provided some insight into the mechanisms of mechanical damage to red cells, but many basic questions are still unanswered. Prevention of the syndrome depends on durable prostheses and optimal surgical correction of the anatomical and physiological abnormalities. No direct chemical effects of prosthetic materials on the red cells have been identified. Whether prosthetic devices can result in alteration of the antigenic structure of red cells through mechanical or other trauma remains to be determined.
Thrombosis continues to be a frequent complication of the use of intravascular prostheses. Here, too, mechanical problems of blood flow are significant. Areas of low pressure and stagnation of flow predispose to thrombosis. Surface properties of implants are undoubtedly important, but present in vitro tests correlate rather poorly with in vivo results. Direct platelet damage due to prosthetic devices has not been demonstrated.
No clinical problems have arisen that suggest any direct effects of implants on white cells or plasma.
Sears, D. A.
Walter Reed Army Institute of Research, Washington, D.C.