Clinical applications of cardiac assist systems continue to have a severe problem, that of thromboembolic complications. The problem originates mainly at the valves, which are usually made of a antithrombogenic material, such as bovine pericardium. However, the valve housing is made of a less suitable material, and wherever the blood flow is stagnant, 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 sinuses. Consequently, thrombi often are generated in the sinuses. The novel valve design presented in this article avoids the formation of the 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 of the res purges the sinuses. The purge flow effect is investigated with an experimental method in which the sinus is filled with dye, and washout during the valve action is observed and recorded on videotape, which is compared with washout in a valve without a purge flow. In addition, the purge flow effect is investigated by computational fluid dynamics. Both methods show that the purge flow effectively increases fluid exchange in the sinuses.
Copyright © 1998 by the American Society for Artificial Internal Organs