Aortic stenosis is a term used to describe congenital heart defects that cause obstruction of blood flow from the heart to the body. Significant aortic stenosis is relatively uncommon affecting about 6 of every 1000 babies born and occurs more often in boys. It can occur alone, that is without other heart problems, or in association with bicuspid aortic valve, coarctation of the aorta, ventricular septal defect, mitral valve abnormality, and less commonly with atrial septal defect or complete atrioventricular septal defect.
In the normal heart, red blood returning from the lungs, flows from the heart's left upper chamber called the left atrium (1) through the mitral valve to the left ventricle (2) where it is pumped through the aortic valve and out to the body. When a child has aortic stenosis, the area where blood exits the heart's lower left chamber is too narrow. Usually, the aortic valve itself is affected and this is called valvar aortic stenosis. See(3) in the figure below. This problem can be caused by fusion of the valve leaflets; a condition called bicuspid aortic valve.
In more severe forms of valvar stenosis, the fibrous ring of tissue that supports the valve is also small and underdeveloped. Subvalvar aortic stenosis is the term used when the narrowed area is below the valve (1) in the figure below.
Supravalvar aortic stenosis is the term used when the narrowed area is above the valve (1) as shown in the figure below.
Like most heart defects, aortic stenosis does not have an adverse affect until after a baby is born. The health effects of aortic stenosis are related to the degree of the narrowing, valve leaks, and if there are other heart defects.
Whether the degree of narrowing is measured as the pressure difference across the area. The higher the number, the greater the problem, since the left heart has to work much harder to pump blood to the body. Trivial aortic stenosis is when the narrowing is less that 20 mmHg. Mild aortic stenosis is when the pressure difference is less than 30-40 mmHg, moderate aortic stenosis is when the pressure is 40 to 50-60 mmHg, and severe aortic stenosis is when the pressure is greater than 60-70 mmHg. Critical aortic stenosis is a term used in newborns with very severe narrowing (greater than 90 mmHg) and requires treatment soon after birth.
The more severe the problem, the harder the left ventricle (left-sided pumping chamber) has to work. Over time, if the problem is not treated, this overwork causes a thickening of the heart muscle called ventricular hypertrophy. Eventually, the muscle becomes damaged resulting in left-sided heart failure and abnormal heart rhythms.
When the aortic valve is affected, there may be leaking of the valve in addition to the narrowing. Terms used to describe the severity of valve leakage include trivial, mild, moderate, and severe. The more the valve leaks, the harder the heart, specifically; the left ventricle has to work to pump blood out to the body. The combination of significant leakage and narrowing can cause a great deal of stress on the heart.
The natural history of aortic stenosis is that it tends to progress, that is, become more severe over time. For this reason, periodic visits to a pediatric cardiologist are important. If the narrowing is trivial and caused by a bicuspid aortic valve, it may not progress.
Heart related symptoms are not expected in children with trivial or mild aortic stenosis. Moderate to severe aortic stenosis can cause symptoms that include chest pain during exercise, low stamina, palpitations (feeling skipped beats), shortness of breath during exercise, dizziness, and/or fainting. In a child with aortic stenosis, these symptoms should be reported to the child's doctor as they may indicate the need for treatment.
In a baby born with critical aortic stenosis, the opening is so small that the heart cannot pump enough blood to meet the baby's needs. Unless the problem is treated early, the baby will develop problems with shock and congestive heart failure. A medication called prostaglandin may be used to keep the ductus arteriosus patent or open. The ductus arteriosus is a small blood vessel that connects the pulmonary artery with the aorta and provides a way for blood to get out to the body. The blood that exits the heart by the ductus arteriosus bypasses the lungs so the baby may look a little blue.
Children with aortic stenosis are at increased risk for subacute bacterial endocarditis (SBE). This is an infection of the heart caused by bacteria in the blood stream. It can occur after a dental or other medical procedure and can largely be prevented by a dose of antibiotic prior to the procedure.
Participation in physical activities and sports: Exercise recommendations are best made by a patient's doctor so that all factors can be included in the decision. Children with aortic stenosis can participate in recreational physical activities but are usually restricted from competitive and vigorous athletic activities. If the aortic stenosis is trivial, they may be permitted to participate in competitive athletics but will need to see their cardiologist regularly to make sure that the narrowing has not progressed.
Prenatal diagnosis: The diagnosis of aortic stenosis is made by an echocardiogram of the baby's heart and can be made as early as 16 weeks into the pregnancy. An echocardiogram of the heart is done when a possible problem is identified during a routine prenatal ultrasound or because of a family history of congenital heart disease. Left sided heart problems tend to recur in families where one child is affected. Estimates of having another child affected range from 4.5 to 13% (Boughman et al. 1993, Brenner et al. 1989). If there is a family history or if concern is raised during a routine ultrasound, the family is referred to a pediatric cardiology center where a detailed ultrasound of the heart is performed.
Symptoms: Symptoms of aortic stenosis are related to the degree of narrowing, leakage, and the presence of other heart problems. Mild aortic stenosis usually does not cause heart-related symptoms. More severe aortic stenosis may cause chest pain that is related to exercise, decreased stamina, palpitations or "skipping beats", and/or fainting. Undetected aortic stenosis can cause sudden death during vigorous physical exertion. Critical aortic stenosis in an infant can cause congestive heart failure with symptoms of poor feeding, rapid breathing, clammy sweating, lethargy, and/or irritability.
Physical findings: Aortic stenosis is often diagnosed due to the presence of a heart murmur. Infants may have symptoms of congestive heart failure as described above as well as weak pulses.
Medical tests: The gold standard for diagnosis is an echocardiogram. Cardiac catheterization is done if there are any questions not clearly answered by the echocardiogram and may also be done for therapeutic purposes, that is, to perform a balloon dilatation or angioplasty.
Medical decision-making for patients with aortic stenosis includes many factors including the location of the narrowing, severity of narrowing, associated cardiac problems, symptoms, age, and size. Valvar aortic stenosis can be treated surgically or by balloon dilation, a procedure done in the cardiac catheterization lab. For the most part, other types of aortic stenosis are treated surgically. These procedures are done to open up the area of obstruction to decrease the amount of work the left ventricle has to do to get blood out to the body. This helps to protect the heart muscle from overwork and later development of heart failure and/or abnormal heart rhythms.
Balloon angioplasty for valvar aortic stenosis:
As described earlier, aortic stenosis often progresses over time. Balloon angioplasty may be the only intervention required but is often used as a temporary means to delay open-heart surgery. This procedure is done in the heart catheterization laboratory. During the procedure, catheters (thin plastic tubes) are placed into the large blood vessels in the legs and gently guided to the heart. The catheter tip is placed across the aortic valve and the balloon tip is inflated. The balloon gently dilates the narrowed area. The incidence of complications is low and includes damage to the femoral artery, bleeding, perforation, and aortic valve leakage.
Surgery for valvar aortic stenosis:
Surgical valvotomy: When the surgeon performs this operation an incision is made down the center of the breastbone. The heart is stopped for a brief period of time while the body is supported with a heart lung bypass machine. The defect is then fixed by making an incision into the ascending aorta where it exits the left ventricle. An instrument called a dilator is then placed through the aorta and through the opening of the aortic valve stretching it. Progressively larger dilators are used until the valve is opened as much as possible without overstretching the valve which would allow it to leak blood backwards into the ventricle.
Valve replacement surgery: Sometimes the aortic valve is too narrowed or too leaky to repair. When this happens the aortic valve will eventually need to be replaced. There are criteria that the cardiologist uses to decide when the operation should be done. The goal is to identify when the valve function is poor enough to cause overwork for the heart but before there is permanent damage. This is done through the history and physical examination as well as heart tests done during routine clinic visits.
There are several types of valve replacement operations and the choice of which operation is best for a child is decided through discussions with the parents, the pediatric cardiologist, and the pediatric cardiac surgeon.
Valve replacements alone are not always enough to relieve the narrowing out the ventricle. Sometimes the whole area leading out of the ventricle to the aorta is too small. The supporting structure of the valve, called the valve annulus, may be too narrow even if the leaflets are opened up as far as possible. In these cases the valve replacement is performed with a procedure called a Konno procedure. This involves enlarging the left ventricular outflow tract and the valve ring. It is done through an incision into the outflow tract of the right ventricle and the septum or wall between the right and left ventricles. A patch is placed in this area that enlarges it. The Konno procedure can be done with any type of aortic valve replacement.
Ross procedure: This is one type of valve replacement operation. The surgeon makes an incision down the center of the breastbone. The heart is stopped for a brief period of time while a heart lung bypass machine supports the body.
The coronary arteries are removed from the aortic valve and the diseased aortic valve is removed. The person's own pulmonary valve is then removed from its position in the right ventricular outflow tract and sewn into place as the new aortic valve. The coronary arteries are then reattached to the new valve. A tissue valve, called a homograft or an allograft, is then sewn in the place where the person's own pulmonary valve was removed. This valve is from a human donor and is not live tissue so it will not be rejected by the person's own immune system. It is expected that the tissue valves will need to be replaced in five to ten years but since this is a fairly new procedure the actual frequency of valve replacements is not yet known.
Mechanical valve replacement: When the surgeon performs this operation an incision is made down the center of the breastbone and the heart is stopped for a brief period of time while the body is supported by the heart-lung bypass machine. The coronary arteries are removed from the diseased aortic valve and the valve is removed. A prosthetic valve is then inserted into the aortic valve ring (annulus) and the coronary arteries are reimplanted. The mechanical valve works like a human valve, opening to let blood out of the heart and closing to keep blood from the body from getting back into the heart. It makes a clicking noise when closing that may be heard when the room is quiet or when listening near the chest.
In order to prevent clots from forming on the valve, people with mechanical valves must take a blood thinner called warfarin (Coumadin) for the rest of their lives. Blood tests are done, usually once a month; to make sure that the blood is thinned enough to prevent clots but not so much that the person is at risk for bleeding.
Mechanical valves usually last a long time, potentially for life, without needing to be replaced. A disadvantage is that the person must always take blood thinners. The use of Coumadin during pregnancy is associated with birth defects and early fetal demise, so this may not be the operation of choice for women of childbearing age.
Surgery for subvalvar aortic stenosis: Subvalvar stenosis can be caused by a discrete membrane or by thickened muscle.
Repair for discrete membranous stenosis is done to prevent damage to the aortic valve and to preserve left ventricular function. When the surgeon fixes this defect, an incision is made down the center of the breastbone and the heart is stopped for a brief period of time while a heart-lung bypass machine supports the body. An incision is made in the aorta and the surgeon looks through the valve to visualize the membrane. The membrane is cut away along with a tiny pie shaped wedge of muscle. This is called membrane resection with myectomy and decreases the chances that the membrane will grow back.
Muscular subaortic stenosis is a more diffuse narrowing that sometimes involves the mitral valve. The operation is performed in the same manner as discrete subaortic stenosis using the heart lung bypass machine. The surgeon incises the aorta and looks through the aortic valve to cut away the thickened muscle tissue. Care is taken to avoid the mitral valve structures. This type of narrowing is more difficult to treat and another operation to enlarge the entire left outflow tract may be required at a later time.
Surgery for supravalvar aortic stenosis: When the surgeon fixes this defect, an incision is made down the center of the breastbone and the heart is stopped for a brief period of time while a heart lung bypass machine supports the body. The surgeon makes an incision along the length of the narrowing in the aortic wall. A patch is then placed into the area where the incision was made to open the area and relieve the narrowing. The size and length of the patch is determined by the degree of narrowing of the aorta.
Care and services for patients with this problem are provided in the Congenital Heart, Interventional Cardiology and Cardiovascular Surgery clinics at the University of Michigan Medical Center in Ann Arbor.
What is the outlook for children with aortic stenosis?
Overall, the outlook for people with aortic stenosis is very good. Since it is a lifelong problem that tends to progress over time, people with aortic stenosis need to see a cardiologist on a regular basis.
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Written by: S. LeRoy RN, MSN, Louise Callow RN, MSN
Reviewed January, 2010