Dipl.-Ing. Torsten Linde
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According to literature thrombo-embolic complications are mainly related to unphysiologic flow patterns and the respectively high (or low) shear load of the blood cells. The exact correlation and the limits of acceptable shear stresses are not fully clear yet. Some newer results regarding the critical amount of shear stresses and the exposure time to theses shear stresses, after which damage of the red blood cells appears, could be investigated at the Helmholtz-Institute /3/. Klaus extended these studies on platelet damage and compared porcine with human blood /4/. Until today the thromogenic potential of mechanical heart valve prostheses is exclusively tested in animal studies, whereas the selection of the appropriate animal model is still controversial.
According to today's knowledge the amount of shear stresses and the exposure time of blood cells to these shear stresses are crucial for blood damage. High shear stresses activate platelets and damage red blood cells (RBCs). Shear stresses may be used as a link between computable flow patterns and the physiologic process of thrombus formation. Thrombi are preferentially formed in areas of low shear from platelets that were before exposed to overcritical shear for an overcritical period of time.
The project ThomboSIM is subdivided in two parts. On one hand, the thrombogenicity of mechanical heart valve prostheses is tested in vitro in a self developed "thrombosis tester for heart valves". On the other hand, the flow patterns in these prostheses are analysed via transient flow field simulation.
The primary goal of the project is to clarify the relationship between geometry, flow patterns and risk of local thrombus formation in mechanical heart valve prostheses by correlation of experimental and numerical data. Furthermore, an efficient tool shall be developed for design optimization of mechanical heart valve prostheses, which helps to reduced the number of animal trials.