Changes in blood filtrability and platelet aggregability in patients with aortic valve replacements

Platelet aggregation and blood filtrability were studied in patients with aortic Starr Edwards valves and xenograft valves and in age and sex matched patients with unoperated aortic valve disease and in controls. Blood filtrability was found to be significantly impaired in both patients with aortic valve disease and with Starr Edwards valve replacements. Platelet aggregation in stirred whole blood was found to be significantly greater only in patients with Starr Edwards valves. Red cell release of adenosine diphosphate under shear stress is thus unlikely to mediate the reduced platelet survival in vivo or the increased platelet aggregability in vitro seen in patients with aortic Starr Edwards valves, and it is suggested that the platelets themselves are affected by contact with such prosthetic valves. The relevance of these findings to the risk of thromboembolism is discussed.