Chairman, Robert and Suzanne Tomsich Department of Cardiovascular Medicine
Specialties: Coronary artery disease, arterial bypass grafting, valvular heart diseases, reoperations, diseases of the thoracic aorta, idiopathic hypertrophic subaortic stenosis, and laser transmyocardial revascularization surgery.
Hello, I'm Dr. Bruce Lytle and during the 28 years that I've been a cardiac surgeon at the Cleveland Clinic, one of the most common issues that we've talked with patients about is what kind of operation to have when the aortic valve needs to be repaired or replaced. There are a lot of good operations for aortic valve replacement, but there is no operation that is perfect for every patient. There are a lot of choices and those choices can be confusing.
Basically, aortic valve operations fall into two main groups. One group is the replacement of the aortic valve with mechanical aortic valve prosthesis. The second group represents a series of operations usually involving tissue valves that are used to treat the aortic valve. The purpose of those operations is to avoid taking Coumadin.
Today, mechanical aortic valve prostheses function extremely well and are very long lived. The chief advantage of having a mechanical aortic valve replacement is that the intrinsic failure of that valve is at least over 25 to 30 years, which is the length of time we followed patients with these types of prostheses in place. Intrinsic valve failure is extremely uncommon. The disadvantage of having a mechanical aortic valve is that it is necessary to take [Coumadin]Warfarin, an anti -coagulant. An anti-coagulant is a drug that makes the blood take longer to clot. If someone does not take anticoagulants, there's a risk of blood clots forming on the heart valve. There are a number of disadvantages of taking Warfarin or Coumadin.
One of the disadvantages would include if someone has a medical condition like bleeding ulcers, frequent nose bleeds, or severe hypertension, which would pose a risk if they're taking anti-coagulants. A second problem is that it is necessary to take a drug every day and requires attention to the details of doing that. The third disadvantage revolves around life style changes. Warfarin makes the blood take longer to clot, so if someone taking the medication gets involved in major trauma, that can conceivably be a major problem.
If someone's lifestyle includes activities such as downhill skiing, dirt-bike racing, and playing amateur football, those activities carry with it a trauma risk to someone that is taking Warfarin. Another disadvantage of mechanical valves is that although the likelihood of needing another operation is low, it is not zero. By the time someone has a mechanical aortic valve in place for 20 years the likelihood that they would have had another operation is somewhere around 20%.
A series of other operations have developed that are designed to avoid the need to take Warfarin. Most of those operations involve replacement of the aortic valve with some type of tissue. These procedures include a heterograph, which is a cow valve or a pig valve; an aortic valve homograft, which is a human valve transplant; or an operation called the Ross operation or pulmonary auto-transplantation, where the pulmonic valve is used to replace the aortic valve and then the pulmonic valve is replaced with a homograft. All of these operations have advantages and disadvantages.
The most common tissue valve-type operation is replacement of the aortic valve with either a pig valve or a cow valve. The advantage of that strategy is that it is a very standard operation that is carried out at extremely low risk, and it is not necessary to take Warfarin. The disadvantage of this and all other operations involving tissue valves is that they can eventually wear out. The likelihood of a heterograph wearing out is age related. The older someone is, the more slowly these valves wear out. So for someone over 65 years of age, the likelihood that they would need another operation 15 years after their first operation is about 15%.
An aortic valve homograft is a human valve transplant. It had been our hope since the late 1980's and early 1990's that aortic valve homografts would last longer than heterografts. Unfortunately, that has not turned out to be the case. They appear to wear out at about the same rate. The disadvantages of homografts are that the operation to put one in is a primary operation and is bigger than the operation to put in a heterograft. The re-operation for a homograft is also considerably more difficult than a re-operation for a heterograft. Now, fortunately, in experienced hands, we've found that the risk of doing those homograft re-operations has been relatively low, but they are bigger operations than the re-operation of a heterograft. Therefore we do not choose to use homografts, except in a couple of very specific circumstances. One is in the treatment of valve infections, where homografts represent a very good option and have a very low rate of re-infection. The second is to treat situations where the original valve that was put in appears to be a bit too small for the patient, since homografts are a very efficient valve and relieve the obstruction across small valves extremely effectively.
Another strategy that was developed actually quite a long time ago for replacing the aortic valve is called the Ross operation. This involves taking the pulmonic valve and transplanting it to the aortic valve and then replacing the pulmonic valve with a homograft. The reason that that was originally thought to have been a good idea, and why a lot of these operations have been preformed, was the hope to have [a] permanent aortic valve prosthesis, and then to do a bunch of re-operations for the pulmonic valve over time. Unfortunately, it has turned out that the total re-operation rate for the Ross operation has been somewhere in the neighborhood of 20-25% ten years after the operation, which is higher than the rate for heterografts. The situation where the Ross operation clearly has a real advantage is in children or young adults where the Ross replacement can grow with time. So, if it is important that the aortic valve prosthesis get bigger as the patient gets bigger, that is possible with the Ross operation. The use of the Ross operation is most effective for someone who is in their teens and even younger.
What this all adds up to is that there is no perfect operation. In general as patients get older we tend to use many more biologic prosthesis-usually heterografts. As we get older the risks of taking Coumadin become greater and the likelihood of valve failure become less. With someone who is younger, we tend to have the option of having a mechanical valve just because it can give us better longevity. However, the patient’s preference is extremely important in this area and we use a lot of biologic valves for patients in their 30's and 40's who wish to remain active and not to change their lifestyle.
Fortunately, the risk of a re-operation for a heterograft, particularly a first re-operation, has been extremely low in experienced hands so we're not reluctant to do that. It is very important to remember that the patient’s preference plays a tremendous role in the choice of operation, because there is no operation that has distinguished itself as superior for everybody. When contemplating having an aortic valve replacement, it is important to have a detailed talk with your surgeon about the choices involved and depict the situation that is most likely to be the best for you. Thank you very much.
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