Aortic Stenosis
By DrRich
What is aortic stenosis?
The aortic valve guards the opening of the left ventricle.
(Click here for a quick and easy review of the heart's chambers and valves.) The aortic valve opens as the left ventricle begins to pump, thus
allowing the blood to flow out of the heart.
When the ventricle has finished beating, the aortic valve closes to keep
the blood from washing backwards (regurgitating) into the left ventricle.
In a person with aortic stenosis, the aortic valve no longer opens completely
- that is, the valve becomes partially obstructed. This means the heart must
work much much harder than normal to eject blood.
Over time, the heart begins to fail.
What causes aortic stenosis?
Degeneration and calcification.
The
most common cause of aortic stenosis is, essentially, “wear and tear.”
In some individuals, with the passage of time the aortic valve begins to
degenerate, and when this happens calcium accumulates on the valve, creating
irregular, rock-like deposits. These
calcium deposits infringe on the valvular opening, causing a narrowing of that
opening, or aortic stenosis.
Bicuspid aortic valve. About 1% of all males are born with a bicuspid aortic valve. (That is, their aortic valves, which are supposed to have three cusps, have only two.) Bicuspid valves are especially prone to developing degeneration and calcification, and thus aortic stenosis. Men with aortic stenosis due to bicuspid valves develop symptoms in their 40s and 50s. In contyrast, patients whose degenerative aortic stenosis develops on normal, tricuspid valves begin to have symptoms two or three decades later.
Rheumatic heart disease.
Fifty years ago, rheumatic heart disease
was the leading cause of aortic stenosis in the developed world. With the advent of antibiotics, rheumatic fever has become
relatively uncommon, and so has rheumatic aortic stenosis.
Congenital aortic stenosis. While aortic stenosis associated with bicuspid aortic valves is, strictly speaking, a form of congenital aortic stenosis, it is generally classified with the degenerative aortic stenoses. Included in the congenital category are various malformations of the aortic valve itself, as well as obstructive membranes or muscular growths that form above or below the actual aortic valve. These congenital lesions appear in much younger people than the non-congenital aortic stenoses (usually in children, or occasionally in young adults), and these young patients are more prone to sudden death than older patients with aortic stenosis.
How is aortic stenosis diagnosed?
Doctors become suspicious of aortic stenosis when patients complain of symptoms (shortness of breath, reduced exercise tolerance, chest pain, lightheadedness, or blackout spells), and by examining the heart (and noting the presence of a heart murmur – caused by the blood being forced through the narrow opening of the aortic valve - or an extra heart sound, called the “S4 gallop”).
Once the doctor becomes suspicious of aortic stenosis, the diagnosis can be easily confirmed or ruled out by an echocardiogram.
It is important for doctors to remember that "classic" symptoms of aortic stenosis may not appear in elderly patients, so it is not uncommon for aortic stenosis to be missed in these patients until it becomes very risky to perform corrective surgery. It must especially be remembered that old age does not cause shortness of breath, chest pain, or blackout spells. These symptoms always need a thorough medical evaluation.
How is aortic stenosis treated?
Medical therapy. There is no medical therapy for aortic stenosis. When a patient’s heart problem is caused by a physical obstruction to blood flowing out of the heart, the only effective treatment is to relieve the physical obstruction. This means surgery. While various drugs used for heart failure (digitalis and diuretics for instance) can ameliorate symptoms for a short time, these drugs do not halt the progression of the disease, nor do they significantly delay the patient’s demise.
So with aortic stenosis, the question is not whether to do surgery, but when.
Surgical therapy.The treatment of aortic stenosis consists of replacing the native valve. Operative mortality for aortic valve replacement is approximately 3 – 5%. The risk, obviously, is higher in elderly patients or those with additional medical problems. Approximately 85% of patients having aortic valve replacement will live for at least 5 years after surgery.
The timing of valve replacement surgery
As a general rule, because valve replacement surgery is such a large procedure, valve replacement surgery should be withheld until the heart’s compensatory mechanisms begin to fail.
As long as the ventricle can compensate for the obstruction to blood flow, the patient’s native valve should be left in place. But as soon as the patient’s ventricle begins to fail, and certainly at the first sign of symptoms, valve replacement should be planned.
For this reason, patients with known aortic stenosis should be followed by a cardiologist, with periodic echocardiograms to evaluate the status of the valve opening and the function of the left ventricle.
The good news about surgery for aortic stenosis is that, because severe obstruction to the outflow of blood from the heart is being suddenly relieved, in most cases the function of the heart improves dramatically and immediately. Once the patient recovers from the operative procedure, they almost always feel much, much better than they did prior to surgery.
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