The first mechanical prosthetic heart valve was implanted in 1952. These valves have progressed from simple caged ball valves, to modern bileaflet valves. Heart valves are designed to fit the peculiar requirements of blood flow through the specific chambers of the heart, with emphasis on producing more central flow and reducing blood clots. The caged ball design is one of the early mechanical heart valves, that uses a small ball that is held in place by a welded metal cage. The ball in cage design was modeled after ball valves used in industry to limit the flow of fluids to a single direction.
Natural heart valves allow blood to flow straight through the center of the valve.
This property is known as central flow, which keeps the amount of work done by the heart to a minimum. With non-central flow, the heart must work harder to compensate for the momentum lost to the change of direction of the fluid. Caged-ball valves completely block central flow, therefore the blood requires more energy to flow around the central ball. In addition, the ball is notorious for causing damage to blood cells due to collisions. Damaged blood cells release blood clotting ingredients, hence the patients are required to take lifelong prescriptions of anticoagulants.