Aortic Stenosis for Dummies

Aortic Stenosis at a Glance

1. Aortic stenosis is narrowing of the aortic valve, impeding delivery of blood from the heart to the body.
   
2. Aortic stenosis can be caused by congenital bicuspid aortic valve, scarred aortic valve of rheumatic fever, and wearing of aortic valve in the elderly.
   Aortic stenosis can cause chest pain, fainting, and heart failure leading to shortness of breath.
   
3. Echocardiogram and cardiac catheterization are important tests in diagnosing and evaluating severity of aortic stenosis.
   
4. Patients with aortic stenosis are usually given antibiotics prior to any procedures which might introduce bacteria into the bloodstream, such as dental procedures and surgeries.
   Patients with aortic stenosis who have symptoms may require surgical heart valve replacement.
   

• What causes aortic stenosis?
  In adults, three conditions are known to cause aortic stenosis.
  Progressive wear and tear of a bicuspid valve present since birth (congenital).
  Wear and tear of the aortic valve in the elderly.
  Scarring of the aortic valve due to rheumatic fever as a child or young adult.
  

Bicuspid aortic valve is the most common cause of aortic stenosis in patients under age 65. Normal aortic valves have three thin leaflets called cusps. About 2% of people are born with aortic valves that have only two cusps (bicuspid valves). Although bicuspid valves usually do not impede blood flow when the patients are young, they do not open as widely as normal valves with three cusps. Therefore, blood flow across the bicuspid valves is more turbulent, causing increased wear and tear on the valve leaflets. Over time, excessive wear and tear leads to calcification, scarring, and reduced mobility of the valve leaflets. About 10% of bicuspid valves become significantly narrowed, resulting in the symptoms and heart problems of aortic stenosis.
The narrowing from rheumatic fever occurs from the fusion (melting together) of the edges (commissures) of the valve leaflets.

Patients with mild aortic valve narrowing may experience no symptoms. When the narrowing becomes significant (usually greater that 50% reduction in valve area), the pressure in the left ventricle increases and a pressure difference can be measured between the left ventricle and the aorta. To compensate for the increasing resistance at the aortic valve, the muscles of the left ventricle thicken to maintain pump function and cardiac output. This muscle thickening causes a stiffer heart muscle which requires higher pressures in the left atrium and the blood vessels of the lungs to fill the left ventricle. Even though these patients may be able to maintain adequate and normal cardiac output at rest, the ability of the heart to increase output with exercise is limited by these high pressures. As the disease progresses the increasing pressure eventually causes the left ventricle to dilate, leading to a decrease in cardiac output and heart failure.

• The major symptoms of aortic stenosis are:
  chest pain (angina),
  fainting (syncope), and
  shortness of breath (due to heart failure).
  In 4% of the patients with aortic stenosis, the first symptom is sudden death, usually during strenuous exertion.
  
• Fainting (syncope) related to aortic stenosis is usually associated with exertion or excitement. These conditions cause relaxation of the body's blood vessels (vasodilation), lowering blood pressure. In aortic stenosis, the heart is unable to increase output to compensate for the drop in blood pressure. Therefore, blood flow to the brain is decreased, causing fainting.