Aortic Stenosis (cont.)
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:
In 4% 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 three 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 six to 24
months.
Next: What might the doctor find in patients with aortic stenosis? »
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