Aortic valve replacement options

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Aortic valve replacement options

After you and your doctor decide to replace your aortic valve, the next important decision you need to make is which type of replacement valve to use.

During valve replacement surgery, a cardiac surgeon will replace the diseased aortic valve with a new valve. View a slideshow on aortic valve replacement surgery . The two basic categories of replacement valves are:

• Mechanical valves, made of metal, carbon, and/or artificial materials.
• Tissue valves, made of tissue taken from the heart of a pig. The tissue valve category also includes preserved human valves taken from donors.

Tissue versus mechanical valves

The first step in selecting a replacement valve is to decide whether you would benefit more from a mechanical or a tissue valve. While there are a number of characteristics you need to consider in choosing the right valve, the main trade-off is durability versus risk of blood clots.

Durability of a replacement valve refers to how long the valve lasts and your chances of needing a second valve replacement in the future. In general, mechanical valves are much more durable than tissue valves.

• A mechanical valve lasts a long time, at least 20 to 30 years in most cases. The great durability of a mechanical valve makes it less likely that you will have to replace the valve again in your lifetime. While mechanical valves can break down, it is a very rare occurrence.
• A tissue valve, despite chemical treatments to improve durability, typically lasts 10 to 15 years. Tissue valves typically fail because of the same calcification process that is a major cause of aortic valve stenosis. Tissue valves may also tear or become infected. Although tissue valve failure usually happens slowly, it may require a second valve replacement. It is important to note that age is a significant factor that affects the durability of tissue valves.

What is the risk of blood clots?

Blood clotting is the complication most commonly associated with replacement valves. These clots are dangerous when they form in your circulatory system because they can travel into and block small blood vessels that supply blood to your brain or your heart. This can cause a stroke or heart attack (myocardial infarction). In general, mechanical valves have a much higher risk of blood clots than tissue valves.

Because the body recognizes a mechanical valve as artificial, blood has a tendency to clot on the surface of the valve. The valve components are also hard, unlike the soft tissue of a natural valve, and can actually tear the cells in your blood as they pass through the valve. To prevent blood clots, people who receive mechanical valves must take an anticoagulant medication, such as Coumadin, for as long as they have a mechanical valve. This medication, also known as an anticoagulant or a blood thinner, can increase your risk of severe bleeding from an injury and can cause a number of side effects.

Tissue valves have a much lower risk of blood clotting than mechanical valves. It is generally necessary to take blood-thinning medication (such as Coumadin) for several weeks following your valve replacement. After that period, it is recommended that you take aspirin to maintain a tissue valve. While there is a risk of complications associated with tissue valve failure or infection, these complications are relatively rare.

Are human replacement valves available?

While human valves have good all-around characteristics, these valves are limited in availability and can be very costly.

What is a homograft?

Porcine valves are called "heterografts," which means the grafting of a different type of tissue—from an animal. Human valves are called "homografts," which means the grafting of the same type of tissue—from another person.

Who should get a mechanical valve?

The basic reason to get a mechanical valve is that they last longer than tissue valves. The following table lists people who should strongly consider getting a mechanical valve and the reasons in favor of the choice.

Who should get a tissue valve?

As explained above, tissue valves tend to last longer in older people; even in the best cases, however, tissue valves will likely not last longer than 10 to 15 years (although some have lasted up to 20 years). For this reason, tissue valves are most appropriate for people who are less likely to outlive their valves, which includes people who:

• Are over 65.
• Are under 60 and have severe lung disease, severe heart failure, or severe coronary disease.
• Have a life expectancy of less than 10 years.

The main advantage of tissue valves is that recipients only have to take clot-preventing medication for a short period following surgery, after which they can stop taking the medication and just take aspirin. As a result, a tissue valve may also be the best choice when:

• The risks of clot-preventing medication are too great.
• The person does not want to limit activities because of clot-preventing medication.
• The person refuses to take such medication.

Credits

Last updated:	January 24, 2008
Author:	Robin Parks, MS
Reviewed By:	E. Gregory Thompson, MD - Internal Medicine, Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
Editors:	Kathleen M. Ariss, MS, Pat Truman, MATC