Artificial Heart Valves 1952 – From Early Attempts to Modern Technology

The human heart has four one-way valves that control the movement of blood through it. When functioning properly, all of the valves allow blood to flow in one direction and prevent backflow. The mitral and tricuspid valves open and close between the atria and ventricles, while the aortic and pulmonary valves are located in the arteries leaving the heart. The valve leaflets open and close in response to pressures on either side.

When valves do not function properly—for example, when the mitral valve thickens as a complication of rheumatic fever—they must be replaced with artificial ones.

• Stenosis refers to a narrowing of the valve opening that obstructs blood flow.
• Regurgitation refers to backward flow through the valve. 

Modern mechanical valves can remain functional for a patient's lifetime. However, anticoagulants (blood thinners) may be needed to reduce blood clotting caused by damage to red blood cells and platelets. Less durable tissue valves made from pig tissue or a cow's pericardial sac cause less damage. They also do not require anticoagulants, but may need to be replaced. 

When animal tissues are used to make biological valves, biological markers are removed to prevent tissue rejection.

The first artificial heart valve designs used a silicone ball inside a metal cage. As the ball moved back and forth in response to pressure changes, the metal cage acted as a one-way valve. In 1952, the American surgeon Charles Hufnagel implanted a caged-ball valve in a patient with a damaged aortic valve. 

Another American surgeon, Albert Starr, and the engineer Lowell Edwards invented a similar valve. The surgeon used it in a patient in 1960. Later, the moving ball was replaced with a tilting disc, and the use of pyrolytic carbon reduced the formation of blood clots. 

About the Article Image: A Starr-Edwards mitral valve with a moving metal ball.

Historical Figures Mentioned in the Article: Miles Lowell Edwards (1898 – 1982), Charles A. Hufnagel (1916 – 1989), Albert Starr (b. 1926)

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