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Human or animal blood is normally used as a test fluid for the in vitro evaluation of hemolysis by artificial organs. However, blood has some disadvantages (large biological variability and problems with cleaning the devices). For that reason, we searched for a reproducible technical fluid with blood-like flow characteristics that exhibits similar shear depending destruction. In this study, a direct comparison between erythrocyte damage of bovine blood and shear-induced degradation of polyacrylamide solution is given. A uniform shear field was applied to the fluids using a shear device with a plate-plate geometry.It was shown that similarities exist between erythrocytes disaggregation and breakdown of super molecular structures in polymer solutions, caused by mechanical stress. In both cases steady low shear viscositity was diminished and the elastic component of complex viscosity of blood and polymer solutions has been reduced. There is a correlation between shear-induced hemolysis of bovine blood and mechanical polymer-degradation, which depends on the applied shear stresses. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Biological valves exhibit characteristic curves (CC) regarding transvalvular gradient, resistance, and effective orifice area when correlated with a physiological cardiac output range (CO). The slope of the curve of transvalvular resistance over a typical CO range characterizes the clinical performance of the valve. These information may support an individualized decision towards the most adequate valve type. Methods: In an extracorporeal mock circuit two types of stented biological aortic valves (constructed pericardial valves, Edwards Perimount: EP; porcine cusp valves, Medtronic Mosaic: MM) of 21, 23, and 25mm were investigated. Mean transvalvular gradient was measured over a range of 1.9 to 7.2l/min CO at a simulated heart rate of 70beats/min. Transvalvular resistance was calculated and presented as characteristic curves in a log–log-plot against cardiac output. Results: EP valves of all sizes demonstrated low slopes (resistance range; slope: 21mm: 53–79dynesscm−5; 0.29; 23mm: 44–56dynesscm−5; 0.12; 25mm: 38–45dynesscm−5; 0.12) while MM valves exhibited steep slopes (resistance range; slope: 21mm: 46–169dynesscm−5; 0.97; 23mm: 36– −146dynesscm−5; 0.95; 25mm: 27–64dynesscm−5; 0.68) Conclusions: While constructed pericardial valves demonstrate sufficient hemodynamic performance especially in the higher CO range porcine cusp valves exhibited minor resistance in the lower CO range. Patients who exercise regularly may therefore profit from a pericardial valve while patients with a small body surface area and little exercise who therefore remain in the lower CO range may be adequately treated with a porcine cusp valve. [Copyright &y& Elsevier]