Smithsonian museums continue to be closed to support the effort to contain the spread of COVID-19. Read a message from our director, and check our website and social media for updates.

Mending Broken Hearts: Innovation Inside the Body

This website is based on an exhibition that was on view at the National Museum of American History from September 23, 2016 to March 26, 2017.


Approximately 100,000 artificial valves are implanted each year in the United States. But when an artificial heart valve was implanted on September 11, 1952, it was the first successful mechanical replacement of an internal human body part. Developing a successful and reliable mechanical valve entailed years of experimentation with materials and design by doctors, scientists, and engineers.

What are heart valves?

The human heart is a four-chambered muscular organ that pumps blood through the body. It has four heart valves: aortic, pulmonary, tricuspid, and mitral. These valves allow blood to flow in one direction between chambers. The valve’s tissue leaflets or cusps open to let blood flow through and close to prevent blood from regurgitating, or regurgitating flowing back.

Model of a diseased valve
Around 1983

This model of a diseased aortic valve was used by an NIH surgeon to explain valve disease to his patients. 

Loan from Dewitt Stetten, Jr., Museum of Medical Research, National Institutes of Health 

Why replace a heart valve?

When the valve’s leaflets stiffen, the valve cannot open and close properly. Congenital anomalies or diseases such as rheumatic fever or high blood pressure can cause this valve malfunction. Damaged valves restrict blood flow to the body, causing the heart to work harder to circulate blood. If the valves do not function properly they may need to be repaired or replaced.

A diseased aortic valve.

Photo courtesy of CDC/ Dr. Edwin P. Ewing, Jr.