Barbara Walters and Aortic Stenosis

Celebrities deserve the same rights to privacy, with respect to their medical conditions, as everyone else. However, when they chose to go public with details about their health, it can raise the public awareness of medical conditions and aid in education. Such was the case this week with Barbara Walters revelation that she has aortic stenosis and was scheduled to undergo valve replacement surgery.
Aortic stenosis affects approximately 6% of the US population or about 3.5 million people. The incidence increases with age. About 2% of 60 year olds, 3% of 70's and 4% of 80 year olds are affected.
The aortic valve is between the left ventricle (main pumping chamber of the heart) and the aorta (the main artery leaving the heart to the rest of the body). Normally it is comprised of 3 very thin leaflets. When the ventricle squeezes, the force of the blood ejecting opens the valve completely allowing the blood to pass into the aorta. The valve then closes so the blood does not leak back into the heart but continues its forward movement. The gradient, or pressure difference across the valve is normally essentially zero.
Aortic stenosis is a condition in which the leaflets of the valve thicken and stiffen. This then reduces their mobility and the heart is now pumping against a partially closed door. As this process continues the stiffness of the valve progresses and the opening shrinks leading to a significant gradient across the valve. About 15% of the population is born with an aortic valve that has 2 leaflets instead of 3. These valves are more prone to developing aortic stenosis, though usually not until later in life. Some however are tight from birth and require surgery in childhood.
A mean gradient of 40 mm of mercury is generally considered significant. With a gradient of 40 across the valve if the blood pressure measured in your arm is 120/ the pressure within the ventricle would then be 160/. If the gradient was 80 a BP of 120/ would mean the intra-cardiac pressure is 200, and so on. This is not a good situation for the heart.
Another measurement of the valve involves estimating the cross sectional area of the opening. Echocardiography is a good way to view this and an area of less than one centimeter is considered severe aortic stenosis.
As you would expect, the heart has to pump harder to push the blood thru this smaller opening. It causes the muscle to strain and thicken. The jet going thru the narrow opening is like putting your finger over the end of an open water hose. The resulting increased blood velocity can cause the aorta to enlarge. Also the straining of the heart to pump against this resistance can lead to chest pain, rhythm problems, fainting spells and heart failure. When fainting spells or heart failure develop from aortic stenosis there is a 50% risk of dying within 3 years.
For patients with symptomatic or severe aortic stenosis surgery to replace the valve is recommended. This is a mechanical problem and there are no medications to reverse it. There is also no good evidence that diet is implicated in its development or treatment.
Surgery to replace the aortic valve is typically performed thru a sternotomy (splitting the breastbone), however in many cases minimally invasive options are available (see previous post). A procedure to implant aortic valves via a needle stick in the groin is currently under investigation in the US.
There are a number of choices of valve type for replacing the aortic valve. Bioprosthetic or tissue valves are the most common choice in the US. These valves are either the aortic valves from pig hearts or are constructed from the pericardium (sac the heart lives in) of cows or horses. These are mounted on a covered stent and are available in a range of sizes. The advantage of tissue valves is that no medication is required following their implantation. The disadvantage is that they wear out. Current generations of valves have improved durability and their longevity is said to be over 90% at 12 years following implant.
The second most common type of valve is a mechanical valve. These are manufactured from pyrolytic carbon and have a bi-leaflet design. They look like a disc split in half that pivots open and closed with the blood flow. The advantage of this type of valve is that it can last virtually indefinitely. The disadvantage is that a blood thinner (warfarin or Coumadin) is required indefinitely.
These two valve types account for the vast majority of valve replacements.
Other options include homograft (cadaver human) valves and autografts. Autografts involve a procedure known as the Ross procedure in which a patients own pulmonary valve is removed and placed in the aortic position, then a homograft in used to replace the pulmonary valve.
How is a decision made as to which type of valve to implant? In the absence of any mitigating factors, age is a reasonable guideline for deciding. It is generally recommended that individuals less than 65 receive mechanical valves and over 65 lean toward tissue valves. This is NOT a hard and fast rule but a guide, and either valve type can be reasonably placed in either population. Obviously if a patient is unwilling or unable to take a blood thinner and have his blood routinely checked, then a mechanical valve is not for him.
Bottom line is that there are many good options. A thorough discussion of options, pros and cons with your surgeon is imperative prior to proceeding with your surgery