The On-X Aortic Valve is a newer generation heart valve made of a unique material and design characteristics compared with earlier generations of mechanical heart valves. It is the only mechanical valve with FDA and CE approval to be used safely with less blood thinner (warfarin). The On-X Aortic Valve, as a mechanical heart valve, has a much lower risk of reoperation than tissue (bioprosthetic) valves, with the additional benefit of less bleeding risk than other mechanical aortic valves because of the significantly lower amount of blood thinner required.