Nonthrombogenic Surfaces: Critical Review

Abstract

plasma coagulation and of platelet aggregation, the physical chemistry of the activation of clotting and the adhesion of platelets to a surface is not well understood. The selection of materials for construction of artificial devices in contact with the blood has therefore been frankly empirical or, when related to theory, has been based on unproved hypotheses. The degree of blood compatibility that present-day artificial surfaces enjoy is due largely to advances in areas other than surface chemistry, such as fluid mechanics,0 and to the use of anticoagulants. For example, implantation of artificial heart valves is a practical clinical procedure, even though the materials these valves are made of are not passive when tested by specific tests for activation of coagulation and platelet alteration in vitro. Them success resuits in large part from skillful engineering and design, which ensure washing of surfaces by flowing blood and avoid areas of disturbed flow such as stagnation points or recirculating eddies that otherwise might allow buildup of thrombus. Activated clotting factors and altered platelets are swept downstream to be dealt with by natural defenses, and since the surface area of the valve is small, hemostatic elements are not depleted and the economy of the