NOVEL CARDIAC ASSIST VALVE WITH A PURGE FLOW IN THE VALVE SINUS

Clinical applications of cardiac assist systems continue to have a sev ere problem, that of thromboembolic complications. The problem origina tes mainly at the valves, which are usually made of a antithrombogenic material, such as bovine pericardium. However, the valve housing is m ade of a less suitable material, and wherever the blood flow is stagna nt, a thrombus is likely to form. Such stagnant blood flow is found in the space between the housing of the valve and the leaflets, in the s inuses. Consequently, thrombi often are generated in the sinuses. The novel valve design presented in this article avoids the formation of t he stagnation zone in the sinuses by a purge flow. This flow is taken from the main flow through the valve and is directed into each sinus o f the res purges the sinuses. The purge flow effect is investigated wi th an experimental method in which the sinus is filled with dye, and w ashout during the valve action is observed and recorded on videotape, which is compared with washout in a valve without a purge flow. In add ition, the purge flow effect is investigated by computational fluid dy namics. Both methods show that the purge flow effectively increases fl uid exchange in the sinuses.