Aortic stenosis is a narrowing of the aorta, the artery connected to the left ventricle of the heart, through which oxygenated blood flows to return to the body. The most common cause of aortic stenosis is congenital, present at birth. However, rheumatic fever can also cause aortic stenosis, and aging has been linked to calcification of the aortic valve, causing narrowing.
In many cases of aortic stenosis, the valve of the aorta is improperly formed. In the normal heart, the aortic valve has three leaflets, which open when the left ventricle pumps blood into the aorta. Malformations of this valve can fuse the leaflets together, or can result in only two leaves or cusps, called bicuspid aortic valve. Any malformation of the cusps is called valvar aortic stenosis.
A more serious form of valvar aortic stenosis involves both fused leaflets and an underdevelopment of the tissue below the valve, further impeding blood flow to the lungs. Subvalvar aortic stenosis almost always requires immediate surgical intervention. Narrowing can also exist above the valve, called supravalvar aortic stenosis. Trivial and mild aortic stenosis may be left untreated, but necessitate visits to a pediatric cardiologist to make sure the valve is growing properly, and to assess whether the stenosis is worsening. Severe or critical aortic stenosis usually requires surgical intervention.
With a narrowing aorta, the left ventricle must pump much harder to get blood to the body. While the left ventricle is a strong muscle, if it works too hard, the muscle will become hardened and began to enlarge, a condition called hypertrophy. Hypertrophy can ultimately damage the ventricle and cause reduced function. The valve of the aorta may also be leaky, causing some of the blood to flow back into the heart with each pump. This regurgitation can cause hypertrophy and fluid retention.
Less blood going to the body means the tissues are not getting enough oxygen. Over time, untreated aortic stenosis can damage growth, causing clubbing of the extremities, and affect brain development. It can also cause exhaustion, blackouts, and dizziness.
There are essentially three ways to treat aortic stenosis. Balloon valvuloplasty may be used to address mild aortic stenosis. A catheter with a balloon attached is threaded through the heart. In the aorta, the balloon is inflated to attempt to open the valve. This treatment may temporarily cause a wider opening of the aorta, and in mild cases, may cure the condition. Its advantages are that it is a minimally invasive, outpatient procedure.
Often, balloon valvuloplasty fails to provide the desired results, or gradually the aorta becomes stenotic again. In these cases, surgeons recommend replacement of the valve. There are two replacement techniques.
In the first, the surgeon excises the aortic valve and replaces it with a mechanical or pig valve. Mechanical valves work very well, but they have the disadvantage of holding a much higher risk for blood clotting. Most people with a mechanical valve must take warfarin, a blood thinner.
In children, warfarin can be particularly problematic because children are prone to accidents. Warfarin levels are measured so as not to cause excessive bleeding. This can mean several months of weekly blood tests, as well as dietary modifications. Even with monitoring, risk is increased for excessive bruising and bleeding. Even a simple bump on the head may cause concussion.
The Ross procedure is often preferred over mechanical valve replacement. This surgery removes the pulmonary valve and aortic valve, and uses the pulmonary valve to replace the aorta. The pulmonary valve must be replaced by either a pig valve or donor valve. The advantage to this procedure, aside from avoiding the mechanical valve, is that the new aortic valve has a chance to grow and develop normally. Even though the new pulmonary valve will probably need replacement at some point, this is considered a far easier surgery than replacement of the aorta.
All levels of severity of aortic stenosis require lifelong observation by a cardiologist. Even in the least severe cases of aortic stenosis, patients must take antibiotics prior to dental exams and procedures to reduce the risk of bacterial endocarditis. Mild and moderate aortic stenosis can limit activity, especially in competitive sports, though occasional participation in recreational sports is acceptable. A patient's cardiologist will have specific recommendations about what activities can be enjoyed. With surgery, a patient with aortic stenosis has an excellent chance of living a normal and purposeful life.