What is Aortic (Valve) Stenosis?
Aortic stenosis is a condition that causes blocking of blood flow between the left ventricle and the aorta. There are many causes. These causes include muscular obstruction below the aortic valve, a block at the valve itself, or aortic narrowing right above the valve.
The most common form of aortic stenosis is a block at the valve itself. This is called aortic valvar stenosis.
The normal aortic valve consists of three thin and flexible leaflets. When the left ventricle pushes blood into the aorta, normal aortic valves spread apart easily. There is no blockage of the blood going out of the heart.
Aortic stenosis occurs when defects of the aortic valve lead to narrowing and blocks between the left ventricle and the aorta.
The most common defect occurs when the aortic valve has only two (instead of three) leaflets. This is called a bicuspid aortic valve (or BAV). Often the valve leaflets are thicker and less flexible than normal. The lines of separation between them (called commissures) are stuck together. When the aortic valve does not open as easily, the left ventricle must work harder to push blood into the aorta.
To make up for this additional work, the muscle of the left ventricle (the myocardium) slowly gets thicker. That way it can give more strength to left ventricular ejection. The bigger left ventricular muscle (called hypertrophy) is not a problem on its own. Hypertrophy is a sign of valve blocking.
When the aortic valve is really blocked, the left ventricular muscle may not be able to do its job. In these very severe but rare times the left ventricle may not pump blood well. The patient may develop cardiac failure. This mostly occurs in infants with severe valve blockage. Heart failure rarely occurs later in childhood.
Signs and Symptoms of Aortic Stenosis
Children with aortic valvar stenosis are generally healthy. They don’t have symptoms. A heart murmur is the most common sign seen by a doctor that shows a valve problem may be present.
Children with mild-to-moderate degrees of aortic valve stenosis will have easily detectable heart murmurs. They won’t have any symptoms at all.
Symptoms occur with severe aortic stenosis. A newborn with critical aortic valve stenosis develops heart failure in the first days of life. This is an emergency that requires immediate treatment.
In an older child, severe aortic stenosis rarely causes heart failure. The child may have chest pain, lightheadedness or fainting spells with exercise. Severe aortic stenosis is a rare cause of sudden death during sports activities.
Diagnosis of Aortic Stenosis
The diagnosis of aortic stenosis is suspected because a doctor hears a heart murmur or click. There is often a clicking sound when the thickened valve snaps to its open position. These sounds can be found through careful examination of the heart by a doctor.
Other testing may show aortic stenosis. Tests may help document how severe it is. An electrocardiogram is often done. The electrocardiogram is normal with mild-to-moderate aortic stenosis. With severe aortic stenosis, the electrocardiogram can show enlargement of the left ventricle. It may show left ventricular strain
The echocardiogram (or "echo") is the most important test to find and evaluate aortic valve stenosis. The echocardiogram documents that the blockage is present at the valve level. It can estimate the degree of valve obstruction.
The echocardiogram is also important in looking for other problems that may be associated with aortic stenosis. This may include left ventricular failure, coarctation of the aorta, ventricular septal defect or mitral valve stenosis.
Your doctor may order an exercise stress test if your child has aortic stenosis. The exercise stress test gives information about the impact of aortic stenosis on the function of the heart.
During exercise patients with aortic stenosis may show abnormal blood pressure or electrocardiogram changes. These findings may help your doctor to determine that therapy is needed. The absence of such changes may help your doctor know that treatment is not yet needed.
Cardiac catheterization is an invasive technique that allows doctors to measure how much aortic stenosis is present. During cardiac catheterization, pressure measurements are made above and below the valve. This measures the amount of blockage. Pictures are taken to see the degree of valve obstruction.
Echocardiography has replaced cardiac catheterization in many cases to find and measure aortic stenosis.
From time to time, it may be necessary to do a cardiac catheterization to add to the information from the echo studies. Cardiac catheterization can be combined with a balloon dilation procedure.
Treatment for Aortic Stenosis
Children with mild aortic stenosis rarely need treatment.
Aortic stenosis may continue to progress. Children with mild disease may need treatment later in life if their aortic stenosis worsens.
All treatment for aortic valve stenosis is palliative (it does not return the valve to a normal condition). Before and after treatment, it is important that all children with aortic stenosis follow up with a cardiologist for the rest of their life.
The type of treatment needed depends on the type of valve defect. The most common defect is when the aortic valve is of normal size, is bicuspid (that is, two leaflets instead of three), and has a degree of fusion along the commissures (or lines of leaflet opening). This form of aortic valvar stenosis responds well to balloon dilation procedures.
Balloon dilation valvuloplasty is done at the time of cardiac catheterization. It does not require open-heart surgery.
In the newborn, it can be done through the umbilical artery.
In older children, the procedure is done through a femoral artery. Patients are usually kept in the hospital overnight. Balloon valvuloplasty can be done as an outpatient procedure in some children.
Surgical valvotomy is an open-heart procedure where the surgeon opens the valve. In many centers this open-heart procedure has been replaced by the less invasive balloon dilation valvuloplasty technique.
Open-heart surgical procedures are needed for more complex valves. These valves may be blocked by severe calcium deposits in their leaflets. The valve ring may be small and underdeveloped. For these conditions, surgical aortic valve replacement will be needed.
The Ross procedure is an aortic valve replacement option that may be best for young children. In the Ross procedure, the patient's own pulmonary valve is transplanted to the aortic valve position. The pulmonary valve is replaced with a homograft (human donor valve) from the right ventricle to pulmonary artery.
It is a good option for young children because the replaced aortic valve can grow with the child. It also does not need the use of a blood thinner.
A more traditional aortic valve replacement procedure involves the implantation of a mechanical prosthesis in the aortic valve position. Anticoagulation therapy (blood thinner) is needed with any mechanical valve substitute. When the aortic valve is small (also known as a hypoplastic valve annulus or ring), more involved surgical techniques (like the Konno procedure) are required. The Konno procedure makes the aortic valve ring larger with a cut into the wall between the two ventricles. The larger valve annulus can then accept a more normal size prosthetic aortic valve or pulmonary valve auto transplant.
A child with valvar aortic stenosis and a hypoplastic valve ring might require a Ross-Konno procedure. This is a combination of the Ross procedure plus a Konno procedure.
Results of Treatment
Results of balloon dilation valvuloplasty have been excellent. Most large centers have a moderate degree of experience with it. The technique decreases the degree of aortic valve obstruction from severe to mild in a large number of patients.
Children who do not have the blockage significantly improve with a balloon dilation procedure usually have more complex disease.
Balloon dilation valvuloplasty does cause valve insufficiency (or leakage). This is mild in most patients. In about 3% to 5% of the patients, the balloon procedure will create severe aortic valve insufficiency. Severe aortic valve insufficiency may need surgical intervention.
Long-term follow-up studies of balloon dilation valvuloplasty show that relief of blockage lasts for several years.
Like surgical valvotomy in the past, recurrent valve obstruction does occur in many children over the next five to 10 years. Recurrent narrowing is related to patient growth and chronic valve changes. Many of these children will need repeat balloon dilation or surgical valve replacement procedures.
The outcomes of open-heart surgical procedures for severe aortic valvar stenosis have been excellent. The mortality risk for surgical valve replacement, either prosthetic valve or the Ross procedure, is less than 3% in experienced centers. These procedures effectively relieve all aortic stenosis and insufficiency with low complication rates.
When valve replacements occur in young children, the long-term concern is that the child will outgrow the size of the artificial valve. They may need a repeat surgical valve replacement in later years.
When adult-sized artificial aortic valves are implanted in large children and teens, they are expected to last 20 years or more with excellent function.
The Ross procedure has several unique issues that need evaluation as children grow. The patient's native pulmonary valve is implanted in the aortic valve position. It may dilate. This dilation may lead to some degree of valve leakage over time.
A channel is put between the right ventricle and pulmonary artery (to replace the native pulmonary valve). If the Ross procedure is done in an infant or small child, this right-sided channel will need to be replaced as the child grows.
It is important to understand that all treatments for aortic stenosis are palliative, not curative.
A balloon dilation procedure may leave the patient with only mild aortic stenosis, but not a normal valve.
A valve replacement surgery will relieve all outflow blockage but leaves the child with an artificial valve.
Long-term follow-up, with regular evaluations by a cardiologist, is important to give the highest quality outcome for patients with aortic stenosis.
Adult and Adolescent Management
An adult with aortic valvar stenosis requires periodic follow-up. A stenotic or narrow valve tends to become narrower over time. Some patients may need to have an aortic valve replacement. Young adults may be treated with a balloon procedure to open the valve. Activities may be limited when stenosis is becoming severe. Symptoms tend to happen during strenuous exertion. Otherwise, patients with aortic stenosis may do normal activities. These patients are at risk for infective endocarditis (a heart infection). They should maintain excellent oral hygiene and regular dental care.
Many adult patients also have some leakage of the aortic valve, called aortic regurgitation (AR). They may have narrowing and leakage of their valve. There are guidelines that we follow to help us decide what the best strategy is for each patient.