Artificial heart valve facts for kids

Kids Encyclopedia Facts

Quick facts for kids Artificial heart valve
Different types of artificial heart valves
Specialty	cardiology

An artificial heart valve is a special device placed inside a person's heart. It replaces a natural heart valve that isn't working correctly. These artificial valves help blood flow smoothly through the heart.

Your heart has four important valves: the tricuspid valve, pulmonary valve, mitral valve, and aortic valve. They act like one-way doors, making sure blood always moves in the right direction. Sometimes, a heart valve can become stiff, making it hard for blood to pass through. Other times, a valve might leak, letting blood flow backward. Both of these problems can make your heart work harder. When this happens, doctors might need to replace the faulty valve with an artificial one.

Understanding Artificial Heart Valves

How Your Heart Valves Work

Your heart has four valves that open and close with each heartbeat. They guide blood through your heart and out to your body.

Blood first enters the right side of your heart.
It goes through the tricuspid valve to the right ventricle.
Then, it's pumped through the pulmonary valve to your lungs to pick up oxygen.
Oxygen-rich blood returns to the left side of your heart.
It passes through the mitral valve to the left ventricle.
Finally, the left ventricle pumps this blood through the aortic valve to your whole body.

A 3D view of an artificial heart valve inside the heart.

Why Valves Might Need Replacing

Heart valves can get damaged for different reasons. Sometimes, people are born with valves that don't work perfectly. Valves can also wear out as people get older. Illnesses like rheumatic fever or infections can also harm them. High blood pressure or past heart problems might also cause damage. When a valve is too damaged, an artificial one can help.

Types of Artificial Heart Valves

There are three main kinds of artificial heart valves:

Mechanical heart valves are made from strong, man-made materials.
Bioprosthetic tissue valves use animal or human tissue.
Tissue-engineered valves are still being developed in labs.

Mechanical valves are often used in some parts of the world. Bioprosthetic valves are more common in other regions.

Mechanical Valves: Strong and Durable

Mechanical valves are built to last a very long time. They are made from materials like metal and a special type of carbon. There are different designs, but the most common one today uses two small flaps. These flaps open and close to control blood flow.

A Look Back: Early Artificial Valves

The idea of replacing a faulty heart valve is not new. In 1952, a doctor named Charles A. Hufnagel tried using a simple plastic tube with a ball inside. This early design helped some patients, but it wasn't perfect.

A big step forward happened in 1960. A brilliant engineer named Miles "Lowell" Edwards worked with a surgeon, Albert Starr. Together, they created the Starr-Edwards valve. This valve had a small silicone ball inside a metal cage. It was the first truly successful artificial heart valve. It helped many patients for decades. Some of these valves worked for over 40 years! However, patients with these valves needed to take special medicine to prevent blood clots. The Starr-Edwards valve was eventually replaced by newer designs in 2007.

The Starr-Edwards caged ball valve.

Tilting-Disc Valves

In 1969, a new type of mechanical valve appeared: the tilting-disc valve. This design uses a single disc that tilts open and closed. It's held in place by a metal ring. The disc is made from a very hard carbon material. This helps the valve last for many years without wearing out.

A tilting-disc valve.

Bileaflet Valves

The bileaflet valve was introduced in 1979. This design has two small, half-moon shaped flaps. These flaps open and close to let blood through. Bileaflet valves have a wider opening than older designs. This means they have a lower chance of causing blood clots. However, sometimes a small amount of blood can flow backward through them.

A bileaflet valve.

Good Things About Mechanical Valves

The best part about mechanical valves is how long they last. Because they are made of strong materials like metal and carbon, they can work well for 20 to 30 years.

Challenges with Mechanical Valves

One main challenge with mechanical valves is the risk of blood clots. These clots can form when blood cells are damaged as they pass through the valve. If a clot travels to the brain, it can cause a stroke. To prevent this, people with mechanical valves must take special medicine called blood thinners every day for the rest of their lives.

Sometimes, mechanical valves can also cause red blood cells to get damaged. This is a condition called mechanical hemolytic anemia. Also, very tiny bubbles can sometimes form near the valve. This can affect how well the valve works over time. In rare cases, the body might not fully accept the artificial valve.

Bioprosthetic Tissue Valves

Bioprosthetic Tissue Valves: Natural Materials

Bioprosthetic valves are made from natural tissues. Most often, these come from animals, like cows or pigs. The animal tissue is carefully prepared so the body won't reject it. It's also treated to stop it from hardening over time.

Sometimes, human tissue is used instead. A homograft is a valve taken from a human donor. This might be from someone who has passed away. Another option is the Ross procedure. In this surgery, a patient's own pulmonary valve is moved to replace their aortic valve. Then, a donor pulmonary valve replaces the one that was moved. This procedure is often good for children because their own valve can grow with them.

Good Things About Tissue Valves

Tissue valves are less likely to cause blood clots than mechanical valves. This is a big advantage. It means people with tissue valves usually don't need to take blood thinners for the rest of their lives. This also lowers their risk of bleeding problems.

Challenges with Tissue Valves

Tissue valves don't last as long as mechanical valves. They usually need to be replaced after 10 to 20 years. This means a person might need more than one surgery during their lifetime. They also tend to wear out faster in younger people.

Over time, tissue valves can also harden, a process called calcification. When this happens, the valve can become stiff and might not close properly. Another challenge is that tissue valves cannot grow or change with a person. So, a child with a tissue valve would need new valves as they grow.

Tissue-Engineered Valves

Growing New Valves in the Lab

For more than 30 years, scientists have been trying to grow heart valves in a lab. These are called tissue-engineered valves. They involve placing human cells onto a special support structure. This structure helps guide the cells to grow into the correct shape of a heart valve.

Scientists can use 3D printing to make these support structures very precisely. The goal is for these new valves to act just like natural ones. They should not cause blood clots, be strong, and resist hardening. Ideally, they would also grow with the patient. Some of these valves have been tested, but they are not yet available for everyone.

Choosing the Right Artificial Valve

Differences Between Mechanical and Tissue Valves

Mechanical and tissue valves are made from different materials. Mechanical valves are usually made of strong metals and carbon. Tissue valves are made from human or animal tissue.

When Mechanical Valves Might Be Better

Mechanical valves can be a good choice for younger people. This is because they last a very long time. They are also good for people who already take blood thinners for other reasons.

When Tissue Valves Might Be Better

Tissue valves are often better for older people. They might not need another valve replacement surgery in their lifetime. They are also a good option for people who cannot take blood thinners. This includes people who plan to become pregnant, as blood thinners can be risky during pregnancy.

How Artificial Heart Valves Should Work

An ideal artificial heart valve should work just like a natural one. Here are some key things it should do:

Minimal Leaking: It should let very little blood leak backward when it closes. A small amount is normal, but too much can be a problem.
Easy Blood Flow: It should not block blood flow too much. Natural valves let blood pass easily, creating very little pressure difference.
No Blood Clots: It should not cause blood clots. Clots can be dangerous if they block blood vessels, leading to a heart attack or stroke.
Self-Repairing: Natural valves can repair themselves a little bit. Currently, artificial valves cannot do this. However, scientists hope tissue-engineered valves might one day have this ability.

Scientists can test how well an artificial valve works in a lab before it's used in a patient.

Repairing Artificial Heart Valves

Artificial heart valves are expected to last between 10 and 30 years.

Over time, artificial valves can start to wear out or develop problems. Sometimes, they might leak or become stiff. Fixing these problems often requires open-heart surgery. Doctors usually try to repair the valve or replace only the damaged part if possible.

Researchers are also looking into new ways to repair artificial valves. They are exploring methods that use small tubes, called catheters. These methods would allow repairs without needing large incisions.