Optimization and investigation of a novel cardiac assist valve with a purge flow.

Clinical applications of cardiac assist systems still suffer from thromboembolic complications due to thrombus formation behind the valve's leaflets. Wherever the flow is stagnant such as in the sinus, a thrombus is likely to form. The valve design in this study avoids stagnation zones behind the leaflets by a purge flow during systole. This purge flow is separated from the valve's main flow by a flow divider directing a part of the main flow into the sinus behind the leaflet. The optimization was performed on a monoleaflet valve because of its simple geometry. Relevant geometric parameters were systematically varied. Thirty-two models were designed and numerically investigated. The models with the best results were preselected and investigated in a computer-controlled valve tester. The washout of a dye filled in the sinus was digitally recorded and quantified. The results show that a sinus purge flow minimizes stagnation areas in the sinus and thus may avoid thrombus formation.