Thrombogenetic studies of bioprosthetic heart valve surfaces. I. In vitro platelet adhesion in a static system

Contact angle measurements, histological examinations and platelet adhesion tests on native and glutaraldehyde-treated porcine aortic valve leaflets, are reported. Contact angles measured with water or saline on native and treated leaflets do not differ appreciably. Values of less than 10 degrees for both the dry and wet leaflets were observed. Histological examination of the native and fixed tissue surfaces was carried out with both optical and scanning electron microscopy. Native leaflet surfaces appeared to be smoother with longer and straighter fibres beneath the surface than treated leaflets. Platelet adhesion tests were performed with fresh, non-anticoagulated human whole blood as well as with platelet suspension. Static platelet adhesion tests were carried out by depositing droplets of blood on the test surface. The blood droplets were washed off after a contact time of 2 minutes for whole blood and up to 32 minutes for platelet suspension. The adhering platelets were microscopically observed and counted. The platelet density on the native leaflets was found to be significantly higher than on the treated tissues. However, the platelet density did not vary with glutaraldehyde concentration in the range from 0.2 to 1.0% (v/v).