July 23, 2016
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Aortic Stenosis (cont.)

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How does aortic stenosis affect the left ventricle pump?

Symptoms and heart problems in aortic stenosis are related to the degree of narrowing of the aortic valve area. 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. An easy way to conceptualize the size issues is to think of a normal aortic valve as being about a "half-dollar" size in diameter, and a significantly narrowed valve to be less than a "dime" in size. 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.

What are the symptoms of aortic stenosis?

The major symptoms of aortic stenosis are:

  • chest pain (angina),
  • fainting (syncope), and
  • shortness of breath (due to heart failure).

In a low percentage of the patients with aortic stenosis, the first symptom is sudden death, usually during strenuous exertion.

The exact reason for sudden death is unknown. It may be due to heart rhythm abnormalities secondary to inadequate blood flow through the narrowed aortic valve into the coronary arteries of the heart. Insufficient oxygen to the inner lining of the heart muscle occurs do to the lack of blood flow to the coronary arteries, particularly during strenuous exercise. Lack of oxygen in the heart muscles causes chest pain and possibly abnormal heart rhythms.

Chest pain is the first symptom in one-third of patients and eventually occurs in one-half of patients with aortic stenosis. Chest pain in patients with aortic stenosis is the same as chest pain (angina) experienced by patients with coronary artery disease. In both of these conditions, pain is described as pressure below the breast bone brought on by exertion and relieved by rest. In patients with coronary artery disease, chest pain is due to inadequate blood supply to the heart muscles because of narrowed coronary arteries. In patients with aortic stenosis, chest pain often occurs without any underlying narrowing of the coronary arteries. The thickened heart muscle must pump against high pressure to push blood through the narrowed aortic valve. This increases heart muscle oxygen demand in excess of the supply delivered in the blood, causing chest pain (angina).

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. Fainting can also occur when cardiac output is decreased by an irregular heart beat (arrhythmia). Without effective treatment, the average life expectancy is less than 3 years after the onset of chest pain or syncope symptoms.

Shortness of breath from heart failure is the most ominous sign. It reflects the heart muscle's failure to compensate for the extreme pressure load of aortic stenosis. Shortness of breath is caused by increased pressure in the blood vessels of the lung due to the increased pressure required to fill the left ventricle. Initially, shortness of breath occurs only during activity. As the disease progresses, shortness of breath occurs at rest. Patients can find it difficult to lie flat without becoming short of breath (orthopnea). Without treatment, the average life expectancy after the onset of heart failure due to aortic stenosis is between 6 to 24 months.

Medically Reviewed by a Doctor on 10/30/2015

Source: MedicineNet.com

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