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Aortic valve replacement is a procedure whereby the failing aortic valve of a patient's heart is replaced with an artificial heart valve. The aortic valve may need to be replaced because:

The valve is leaky (aortic insufficiency, also known as aortic regurgitation)
The valve is narrowed and doesn't open fully (aortic stenosis)

Types of valves

There are two basic types of replacement heart valve: tissue (bioprosthetic) valves and mechanical valves.

Tissue valves
Tissue heart valves are usually made from animal tissue (heterografts) mounted on a metal or polymer support. Bovine (cow) tissue is most commonly used, but some are made from porcine (pig) tissue. The tissue is treated to prevent rejection and calcification (where calcium builds up on the replacement valve and stops it working properly).

Occasionally, alternatives to animal tissue valves are used: aortic homografts and pulmonary autografts. An aortic homograft is an aortic valve from a human donor, retrieved either after their death or from their heart if they are undergoing a heart transplant. A pulmonary autograft, also known as the Ross procedure is where the aortic valve is removed and replaced with the patient's own pulmonary valve (the valve between the right ventricle and the pulmonary artery). A pulmonary homograft (a pulmonary valve taken from a cadaver) is then used to replace the patient's own pulmonary valve. This procedure was first performed in 1967 and is used primarily in children, as it allows the patient's own pulmonary valve (now in the aortic position) to grow with the child.

Tissue valves can last 10–20 years. However, they tend to deteriorate more quickly in younger patients. New ways of preserving the tissue for longer are being investigated. One such preservation treatment is now being used in a commercially available tissue heart valve. In sheep and rabbit studies, the tissue (called RESILIA™ tissue) had less calcification than control tissue.[29] [30] However, long-term durability data in patients are not yet available.[31]

Tissue valves come as stented or stentless. Stented valves come in sizes from 19 mm to 29 mm. Stentless valves are directly sutured at the aortic root. The major advantage of stentless valves is that they limit patient–prosthesis mismatch (when the area of the prosthetic valve is too small in relation to the size of the patient, increasing the pressure inside the valve) and can be helpful when dealing with small aortic root. Their disadvantage is that it is more time-consuming to implant stentless valves than stented valves.

Mechanical valves
Mechanical valves are made from synthetic materials, such as titanium or pyrolytic carbon. They are more durable than tissue valves, typically lasting 20–30 years. However, the risk of blood clots forming is higher with mechanical valves than with tissue valves. As a result, people with mechanical heart valves must take anticoagulant (blood-thinning) drugs, such as warfarin, for the rest of their lives, making them more prone to bleeding. The sound of the valve can sometimes be heard (often as clicks) and can be disturbing.

Valve selection
Valve choice is a balance between the lower durability of tissue valves and the increased risk of blood clots and bleeding with mechanical valves. Guidelines suggest that patient age, lifestyle and medical history should all be considered when choosing a valve. Tissue valves deteriorate more rapidly in young patients and during pregnancy, but they are preferable for women who wish to have children because pregnancy increases the risk of blood clots. Typically, a mechanical valve is considered for patients under 60 years old, while a tissue valve is considered for patients over the age of 65 years.