Congenital Aortic Stenosis

Congenital aortic stenosis refers to an abnormally formed aortic valve which produces varying degrees of obstruction.Patients with mild aortic stenosis have no symptoms while those with moderate and severe aortic stenosis can experience shortness of breath, chest pain, dizziness, or fainting. Patients with symptoms from aortic stenosis as well as those with severe obstruction require treatment to relieve valve obstruction.

The most common form of aortic stenosis is obstruction at the valve itself, referred to as aortic valvar stenosis, which is the subject of this section.

The normal aortic valve consists of three thin and pliable valve leaflets. When the left ventricle ejects blood into the aorta, normal aortic valve leaflets spread apart easily and cause no obstruction to outflow of the blood from the heart.

Aortic stenosis occurs when abnormalities of the aortic valve lead to narrowing and obstruction between the left ventricle and the aorta.

The most common abnormality 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 thickened and less pliable than normal, and the lines of separation between them (or “commissures”) are fused together to a variable degree. When the aortic valve does not open freely, the left ventricle must work harder to eject blood into the aorta.

To compensate for this additional workload, the muscle of the left ventricle (the myocardium) gradually thickens to provide additional strength to left ventricular ejection. The increased left ventricular muscle, also known as hypertrophy, is rarely a problem itself. Instead, hypertrophy is an indication of significant valve obstruction.

When the aortic valve is severely obstructed, the left ventricular muscle may not be able to compensate satisfactorily. In these very severe, but fortunately rare, instances the left ventricle may fail to pump blood effectively and the patient may develop cardiac failure. If this occurs it is almost always in a newborn infant with very severe valve obstruction. Heart failure rarely occurs later in childhood.

Types  of Aortic Stenosis

1.Valvular

2. Supravavular

Localized    :         Hour glass, diaphragm

Diffuse        :         Hypoplastic ascending aorta

3 .Subvalvular

a)     Discrete (Fibrous collar)

b)    Dynamic  (HOCM)

Signs and Symptoms of Aortic Stenosis

Children with aortic valvar stenosis commonly are healthy and have no symptoms. A heart murmur is the most common sign detected by a physician indicating that a valve problem may be present.
Children with mild-to-moderate degrees of aortic valve stenosis will have easily detectable heart murmurs, and typically have no symptoms at all.
Symptoms occur only with severe aortic stenosis. A newborn with critical aortic valve stenosis develops heart failure in the first days of life. This is an emergency situation that requires immediate treatment, either balloon dilation of the valve or surgery.
In an older child, severe aortic stenosis rarely causes heart failure. The child may experience chest pain, lightheadedness or fainting spells particularly associated with exercise. Severe aortic stenosis is a rare, but well-documented, cause of sudden death during strenuous sports activities.

Diagnosis of Aortic Stenosis

The diagnosis of aortic stenosis is usually first suspected because a physician detects a heart murmur or click. The heart murmur of aortic stenosis is a turbulent noise caused by ejection of blood through the obstructed valve. There is often an associated click sound when the thickened valve snaps to its open position. These sounds can be detected through careful examination of the heart by a physician well-trained in cardiac diagnosis.
Other testing may confirm the presence of aortic stenosis and help to document its severity. An electrocardiogram is often obtained. The electrocardiogram is typically normal in the presence of mild-to-moderate aortic stenosis. With severe aortic stenosis, the electrocardiogram can show enlargement of the left ventricle and may even show evidence of left ventricular strain.
The Echocardiogram (or “echo”) is the most important non-invasive test to detect and evaluate aortic valve stenosis. The echocardiogram accurately documents that the obstruction is present at the valve level. It can estimate the degree of valve obstruction.

The echocardiogram is also important in excluding other problems which may be associated with aortic stenosis, such as left ventricular failure, coarctation of the aorta, ventricular septal defect or mitral valve stenosis.
Your physician may also obtain an exercise stress test if your child has aortic stenosis. The Exercise stress test provides information regarding the impact of aortic stenosis on the function of the heart during real-world conditions for children (as opposed to merely studying it at rest).
During exercise patients with important degrees of aortic stenosis may show abnormal blood pressure responses or Electrocardiogram (ECG) changes. These findings may help your physician to determine that therapy is indicated; conversely, absence of such changes may help your physician be assured that treatment is not yet necessary.
Cardiac catheterization is an invasive technique that enables physicians to accurately quantify the degree of aortic stenosis that is present. During cardiac catheterization, pressure measurements are made above and below the valve to measure the amount of obstruction. Motion pictures are taken to visualize the degree of valve obstruction that may be present.

Diagnosis of Biscuspid Aortic Valve

Aortic ejection click

Feature of aortic stenosis and / or regurgitation

Ecentric valve closure in M. mode echo.

Demonstration of two cusps in echo or angiography

Differentiation of sub aortic stenosis from valvular aortic stenosis

Subvalvular obstruction has the following characteristics.

Ejection click is absent

Diastolic murmur or aortic regurgitation is prominent

Post stenotic aortic dilatation is absent

Aortic valve looks normal and has no classification as seen in M mode echo.

Differentiation of Supravavular Aortic Stenosis from Valvular Aortic Stenosis

Supravaluvar stenosis has the following characteristics.

A2 is accentuated unlike valvular AS where it is diminished to absent.

Ejection click is absent

Systolic thrill and murmur are more pronounced and transmitted to neck.

Systolic BP in the right arm is characteristically higher than in the left.

Post stenotic aortic dilatation is absent.

Coronary arterial circulation is abnormal.

Associated Defects of Aortic Stenosis

      Supervalvular Stenosis

Pulmonary artery branch stenosis

     Coarctation

Infantile hypercalcemia, elfin facies, mental retardation.

Treatment of Aortic Stenosis

Children with mild aortic stenosis rarely require treatment.
However, it is important to note that aortic stenosis may be progressive, and that children with mild disease may eventually require treatment later in life.
It is also important to understand that all treatment for aortic valve stenosis is palliative (that is, it does not return the valve to a normal condition). Therefore, before and after successful treatment it is important that all children with aortic stenosis be followed carefully by a qualified cardiologist.
The type of treatment required depends on the type of valve abnormality present. Most commonly, the stenotic aortic valve is of normal size, is bicuspid (that is, two leaflets instead of three), and has a variable degree of fusion along the commissures (or lines of leaflet opening). This “typical” form of aortic valvar stenosis responds very nicely to balloon dilation procedures.
Balloon dilation valvuloplasty is performed at the time of cardiac catheterization and does not require open-heart surgery.
In the newborn, it can be performed through the umbilical artery, thus sparing the use of a small infant’s femoral arteries.
More typically in older children the procedure is performed through a femoral artery. Patients are often observed in the hospital overnight, but balloon valvuloplasty can be done as an outpatient procedure in some children.
Surgical valvotomy is an open-heart procedure during which the surgeon opens the valve along the lines of commissural fusion. In many centers this open-heart procedure has been replaced by the less invasive balloon dilation valvuloplasty technique.
Open-heart surgical procedures are required for more complex valves, where simple balloon dilation does not suffice. These valves may be obstructed by severe calcium deposits in their leaflets, or because the valve ring itself is small and underdeveloped. For these conditions surgical aortic valve replacement will be necessary.
The Ross Procedure is an aortic valve replacement option which may be particularly advantageous for young children. In the Ross Procedure, the patient’s own pulmonary valve is transplanted to the aortic valve position and the pulmonary valve is replaced with a homograft (human donor valve) from the right ventricle to pulmonary artery.
The early to mid-term experience with the Ross Procedure in children has been outstanding. It is a particularly good option for young children because the replaced aortic valve can continue to grow with the child. It also does not require the use of Coumadin anticoagulation therapy (blood thinner).
A more traditional aortic valve replacement procedure involves the implantation of a mechanical prosthesis in the aortic valve position. Anticoagulation therapy is required with any mechanical valve substitute. When the aortic valve is undersized (also known as a hypoplastic valve annulus or ring), more radical surgical techniques (like the Konno procedure) are required. The Konno procedure is a technique which enlarges the aortic valve ring with an incision into the wall between the two ventricles. The enlarged valve annulus can then accept a more normal size prosthetic aortic valve or pulmonary valve autotransplant.
A child with valvar aortic stenosis and a hypoplastic valve ring might require a Ross-Konno procedure, which is a combination of both the Ross procedure plus a Konno procedure.
Results of Treatment
Results of balloon dilation valvuloplasty have been excellent. This technique was developed in the mid-1980s. 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 majority of patients.
Children who do not experience excellent relief of obstruction with a technically adequate balloon dilation procedure usually will have more complex disease, such as calcified valve leaflets or a small valve ring.
Balloon dilation valvuloplasty does cause valve insufficiency (or leakage), but this is mild in the majority of patients. In approximately 3 percent to 5 percent of the patients the balloon procedure will create severe aortic valve insufficiency. Severe aortic valve insufficiency may require surgical intervention (although rarely emergently).
Long-term follow-up studies of balloon dilation valvuloplasty show that excellent relief of obstruction persists for several years.
However, like surgical valvotomy in the past, recurrent valve obstruction does occur in many children during the next 5-10 years. Recurrent narrowing is perhaps related to patient growth and chronic valve changes. Many of these children will require 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 percent 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 and will require a repeat surgical valve replacement in later years.
When adult-sized artificial aortic valves are implanted in large children and adolescents, they are expected to last 20 years or more with excellent function.
The Ross Procedure raises several unique issues which require evaluation as children grow. The patient’s native pulmonary valve is implanted in the aortic valve position, and may dilate. This dilation may eventually lead to some degree of valve insufficiency over time.
In addition, a conduit is placed between the right ventricle and pulmonary artery (to replace the native pulmonary valve). If the Ross Procedure is performed in an infant or small child, this right-sided conduit will need to be replaced later in childhood as the child grows.
It is important to understand that all the treatments for aortic stenosis are palliative, not curative.
An outstanding balloon dilation procedure may leave the patient with only mild aortic stenosis, but not a normal valve.
An outstanding valve replacement operation will relieve essentially all outflow obstruction, but leaves the child with an artificial valve.
Long-term follow-up, with regular evaluations by a qualified cardiologist, is essential to helping provide the highest quality outcome for patients with aortic stenosis.

Complications of Aortic Stenosis

Congestive cardiac failure

Endocarditis

Dissecting aortic aneurysm

Sudden death