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Should Your Replacement Valve Be Made of Tissue or Metal?

Here's what you need to know about both options.

Just as stenting or coronary artery bypass grafting may be needed to improve blood flow through a blocked artery, some heart valves must be replaced for the heart to function properly. Improvements in valve replacement have lessened the risks of this procedure, so the primary issue is choosing which replacement valve will be best for an individual.

"We focus on the longevity of the valve. Mechanical valves last forever. Tissue valves don't," says Cleveland Clinic cardiovascular surgeon Edward Soltesz, MD, MPH.

About Valve Stenosis

Heart valves guide the direction of blood flow through the heart. When the heart contracts, valve leaflets open to allow blood to move into the next chamber. When the heart relaxes, the leaflets close to prevent blood from flowing backwards.

The most common form of valve disease is stenosis. When calcium deposits cause valve leaflets to become stiff, they are unable to open and close properly. This narrows the valve and limits blood flow through the opening. Stenosis tends to affect the aortic and mitral valves, but is particularly urgent when the aortic valve is involved.

"We have learned that irreversible changes to the heart muscle occur in many patients with aortic stenosis even before symptoms appear," says Dr. Soltesz. "We need to act quickly, because the heart can never recover from these changes, and the patient is at an increased risk of death."

Your Replacement Options

There are two types of replacement valves.

* Mechanical valves are made of artificial materials, such as silicone and titanium. They can last a lifetime.

* Bioprosthetic valves are made of cow (bovine) or pig (porcine) tissue. They can last 15 to 20 years. "We favor bovine valves for aortic valve replacement, because they tend to fail slowly, and this is easy to monitor," says Dr. Soltesz.

"Porcine valves typically fail suddenly and unpredictably by tearing. If this were to happen in the aortic position, the patient would require emergency surgery. That's why we use porcine valves in the mitral position. If a mitral valve fails, we can lower the patients blood pressure or use a balloon pump to hold the patient until the valve can be replaced," he explains.

Valves taken from human cadavers are rarely used. That's because they last only 20 years and replacing them requires a far more extensive operation.

Choosing the Right Valve

The choice between a mechanical or tissue valve is based primarily on the patients age.

A mechanical valve is a reasonable option in younger patients, since these valves are unlikely to need replacing during the patient's lifetime.

Durability also makes mechanical valves a good option for patients who are anxious about undergoing surgery, as they are unlikely to need a second replacement.

"Mechanical valves require patients to take anticoagulants for life. However, the risks associated with lifelong anticoagulant use equals the risks of valve replacement surgery, so it's a trade-off," says Dr. Soltesz.

Tissue valves tend to be the first choice for older patients, since they are unlikely to live long enough to need another valve replacement. They do not require anticoagulation. This also makes them a good choice for younger patients who want to be active and don't want to worry about the risks of unwanted bleeding with warfarin.

"The decision on valve replacement is complex. That's why we recommend it be made by a surgeon together with a cardiologist, who can discuss and agree on the best approach for an individual," says Dr. Soltesz.

About the Surgery Itself

Aortic valve replacement can be done in a surgical procedure (surgical aortic valve replacement, or SAVR) or a catheter-based procedure (transcatheter aortic valve replacement, orTAVR). Placing a mechanical valve requires SAVR, since rigid valves cannot be folded and inserted in a catheter.TAVR is a better approach for higher-risk patients, but because it is newer, there is less data on long-term outcomes. "We have been doing surgical valve replacement for years, so we know how long these valves will last. We don't know as much about the durability of TAVR valves," says Dr. Soltesz.

Replacement Valves

Mechanical Valve: The On-X Prosthetic Heart Valve is coated with carbon to deter blood clot formation.

Bioprosthetic valve: The Inspiris Resilia aortic valve is made of bovine tissue specially treated to last longer.

Caption: Image courtesy of CryoLife, Inc.

Caption: Image courtesy of Edwards Lifesciences
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Title Annotation:VALVE SURGERY
Publication:Heart Advisor
Date:Aug 1, 2018
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