Platelet survival in patients with substitute heart valves

Abstract

The hemodynamic benefits of replacing defective heart valves with prosthetic valves are compromised by thromboembolic complications. After replacement of artificial heart valves, platelets are destroyed by prosthetic heart valves, and consumed by interaction with prosthetic valves.It has been shown that patients with substitute heart valves have short platelet survival time, which can be lengthened after treatment with platelet inhibitor drugs as Dipyridamole. For this purpose we have given 450mg daily dosage of Dipyridamole in all patients with prosthetic valves.To determine the relation thromboembolism to the presence of substitute heart valves, kinetic studies of platelet were performed in 14 patients. Six patients had received mitral valve prostheses, 4 had aortic valve prostheses, and 4 had double artificial valves. In accordance with platelet survival half time, platelet survival was determined that it was normal or not. The normal platelet survival half time was 4.0±0.5 days (S. E. M.). Average platelet survival time in 4 patients with aortic artificial valves was 3.85±0.75 days (survival half-time±S. E. M.), in 6 patients with mitral artificial valves, 3.73±0.67 days, and in 4 patients with double prostheses, 3.71±0.74 days. In these patients average platelet survival was almost normal, because they were given Dipyridamole. Thromboembolism occurred in 3 of the 14 patients (21 percent). In this group, platelet survival was shortened in 2 of 3 patients and was normal in one. In these patients, kind of prostheses was Kay-Shiley valve. In spite of treatment with Dipyridamole, it was seen that platelet survival was shortened in 6 patients. In the case of non-thromboembolism episode, it was thought that platelet was destroyed by prothetic heart valves, or was reduced by platelet aggregation and adhesiveness. Therefore there was confirmed that platelet behavior changing factor needed furthermore. In the case of thromboembolism episode, it was thought that platelet was reduced by formation of clot at artificial heart valve and its surrounding. Therefore anticoagulant and fibrinolysin therapy, or artificial valve re-replacement needed in this case.