Aortic Stenosis (AS)
Aortic stenosis may be congenital (birth defect) or acquired. Aortic stenosis accounts for 3-7% of all congenital heart defects. There is a strong male sex predilection: the male-female ratio is 4:1. An estimated 10-15% of patients with AS present with the condition when they are younger than one year.
What is AS?
Aortic stenosis refers to a condition that causes obstruction (stenosis) to blood flow between the left ventricle (main heart pump) and the aorta (major artery). In most patients the obstruction is at the level of the aortic valve but the obstruction could be below the valve (subvalvular AS) or there might be narrowing of the aorta immediately above the valve (supravalvular AS).
The normal aortic valve consists of three thin and pliable valve leaflets (cusps). When the left ventricle ejects blood into the aorta, normal aortic valve leaflets spread wide apart very easily and cause no obstruction to outflow of the blood from the heart.
The most common valve abnormality occurs when the aortic valve has only two, rather than three, leaflets: a bicuspid aortic valve. Many times these leaflets become thickened and less pliable and, in addition, the lines of separation between them (the commissures) may fuse together to a variable degree. When the valve does not open freely, the left ventricle must work harder to pump the blood into the aorta. In mild AS, the heart does not work as hard so the patient remains asymptomatic. In more severe cases the heart needs to compensate for the additional workload. The muscle of the left ventricle gradually thickens (LVH) to provide additional strength for pumping. These patients may experience symptoms and may end up requiring balloon valvuloplasty (using a balloon catheter) or heart surgery. In very severe cases the left ventricle may fail to pump blood effectively and the patient develops heart failure. This occurs almost always in a newborn infant with very severe AS; heart failure rarely occurs later on.
What causes AS?
The etiology of AS is multi-factorial which means that many factors could be involved such as embryologic mal-development, familial cases (genetic), syndromes, environmental factors such as high cholesterol, systemic diseases and others. In most cases the exact cause of AS is unknown. The recurrent risks in offspring of an affected mother is about 15% and of an affected father is about 3%. Most patients with AS have a bicuspid (two-leaflet) aortic valve. Familial screening is recommended as similar or other types of congenital heart defects may be found in family members (20-25% incidence).
What are the symptoms of AS?
Patients with AS are usually asymptomatic and in normal health. Patients with more severe obstruction may complain of shortness of breath (especially during exercise), dizziness, fainting, fatigue and chest pain. A newborn with critical AS develops heart failure in the first days of life. In an older child severe AS rarely causes heart failure. Severe AS is a rare cause of sudden death during strenuous sports activities in athletes.
Patients with AS may develop progressive leakage of the valve (aortic insufficiency) itself. If the leakage is severe enough it may worsen any AS symptoms.
What tests are used to check for AS?
The diagnosis of AS is usually suspected because a doctor detects a heart murmur. There is often an associated clicking sound.
In patients with significant AS, the electrocardiogram can show enlargement or thickening of the left ventricle and in more severe cases a left ventricular strain pattern. An echocardiogram is the most important non-invasive test to detect and evaluate AS. The echocardiogram documents that the obstruction is present and if it is below, above or at the valve level itself. Doppler echo studies are used to estimate the degree of valve obstruction. An echocardiogram also helps in excluding other problems that may be associated with AS such as valve leakage, heart failure and other associated congenital heart defects that may be present.
Your physician may also obtain an x-ray and in some cases an exercise stress test may be indicated. During exercise testing patients with significant AS may show an abnormal blood pressure response or changes in the electrocardiogram. The patient may become symptomatic during the stress testing. These findings will help your cardiologist decide if surgery (or valvuloplasty of the valve itself) is indicated.
From time to time it may be necessary to perform a cardiac catheterization to supplement information obtained with non-invasive data. Cardiac catheterization is also often combined with balloon valvuloplasty (valve dilation) procedure.
What treatments are used in patients with AS?
Patients with mild obstruction rarely require treatment. You should keep in mind that AS may be progressive and that patients with mild obstruction may eventually require treatment later in life. In addition, they may develop aortic valve leakage. This may also need treatment.
It is important to realize that any treatment for AS is just to relieve the obstruction. Surgery does not return the valve to a normal condition. The type of treatment required depends on the type of valve abnormality. Most commonly, the obstructed valve is of normal size and may respond very nicely to trans-catheter balloon valvuloplasty (dilation of the valve). This procedure is performed at the time of cardiac catheterization.
Aortic valvotomy is performed during heart surgery when the cardiovascular surgeon opens the valve. Heart surgery may be required for a more complex valve where balloon valvuloplasty may not help.
Some patients may require aortic valve replacement or a different type of surgery (Ross procedure).
Pay careful attention to optimal dental hygiene by brushing two or three times a day and flossing. Patients with AS no longer require antibiotic prophylaxis for dental procedures but many families may choose to continue with SBE prophylaxis. You should discuss this with Dr Villafañe. Patients who develop progressive leakage may benefit from medicines but may end up requiring surgery, which may involve replacement of the valve itself.
Long-term follow-up with regular appointments with a qualified cardiologist is essential to provide the highest quality outcome for patients with aortic stenosis. Patients with AS may require one or more interventional procedures during their lifetime. This is a life-long process and involves the patient’s family and physician.
Limitations depend on the degree of obstruction and/or leakage. A patient with mild obstruction usually does not have any limitations. Patients with more severe obstruction and/or leakage may be restricted from heavy weight lifting, competitive sports, etc. Specific recommendations regarding sports participations are published by the American Heart Association. You may also like to discuss your questions with Dr. Villafañe.