Innovative developments of the heart valves designed for use in ventricular assist devices

Prosthetic heart valves are routinely used for replacing diseased natural heart valves. Even today, after five decades of prosthetic heart valve development, in the authors opinion the main problem associated with these valves is the risk of thromboembolic complications caused by unnatural hemodynamics. Further growing application of prosthetic heart valves is their use in the pulsatile ventricular assist devices (VADs). VADs may provide life-saving solutions to patients with severe cardiovascular diseases and are superior to drug therapy for patients with severe heart failure. However, the clinical applications of VADs still suffer from thromboembolic complications due to thrombus formations in the vicinity of the valves. Wherever the flow is stagnant or flow separation occurs, a thrombus is likely to form. The design of the heart valves with flow avoiding the formation of stagnant zones is one of the main goals in the development of new valves. This article reviews some innovative design approaches of the valves specially designed for use in VADs. Three design concepts are presented; one is based on the tilting disk valve, the second on the natural valve geometry and the third on the ball valve principle. However, these three different concepts have one common basic idea; the use of the freedom of the valve-housing design. This additional design freedom, which is available in VADs, is a key factor in the development of new valves with optimal hemodynamic performance.