Aortic Stenosis (cont.)
How is aortic stenosis treated?
Patients without symptoms can be observed
until symptoms develop. Patients with mild aortic stenosis do
not require treatment or restriction of activity. Patients with
moderate aortic stenosis (valve area 1.5 to 1.0 square centimeters)
are advised to avoid strenuous activities such as weight lifting
or sprinting. Aortic stenosis can progress over a few years.
Therefore, patients are usually examined annually and evaluated by
echocardiography periodically to monitor disease progression. Since valve infection
(endocarditis) is a serious complication of aortic stenosis, these
patients are usually given antibiotics prior to any procedure
in which bacteria may be introduced into the bloodstream. This includes
routine dental work, minor surgery, and procedures that may traumatize
body tissues such as colonoscopy and gynecologic or urologic
examinations. Examples of antibiotics used include oral amoxicillin
(Amoxil) and erythromycin (E-Mycin, Eryc, PCE), as well as
intramuscular or intravenous ampicillin
(Unasyn), gentamicin
(Garamycin),
and vancomycin (Lyphocin,
Vancocin).
When symptoms of chest pain, syncope, or shortness of breath appear,
the prognosis for patients with aortic stenosis without valve
replacement surgery is poor. Medical therapy, such as the use
of diuretics to reduce high lung pressures and remove lung fluid
can provide only temporary relief of symptoms. Patients with symptoms
usually undergo cardiac catheterization. If severe aortic stenosis
is confirmed, aortic valve replacement is usually recommended.
The overall mortality risk for aortic valve replacement surgery
is about 5%. Advanced age should not be a reason for not recommending
aortic valve replacement for aortic stenosis. Otherwise healthy
patients in their 80s with strong heart muscles often benefit
dramatically from aortic valve replacement for critical aortic
stenosis.
Replacement aortic valves processed from pigs (porcine) or cows
(bovine) are called bioprostheses. Bioprostheses are less durable
than mechanical prostheses (discussed below) but have the advantage
of not needing life-long blood thinning (anticoagulation) medication
to prevent blood clots from forming on the valve surfaces. The
average life expectancy of an aortic valve bioprostheses is 10
to 15 years. Bioprostheses rapidly calcify, degenerate and narrow
in young patients. Therefore, bioprostheses are primarily used
in patients over 75 years old or in patients who cannot take blood
thinners. Recently, aortic valves from human cadavers have been
used in younger patients to avoid the need for anticoagulation
medication. However, the availability of human aortic grafts is limited; though probably better than the other bioprostheses, its long term durability is unknown. The new "Ross
Procedure" consists of moving the pulmonic valve to the aortic position and
replacing the pulmonic valve with a valve from a human donor.
This procedure has not been performed long enough to evaluate
the long-term performance of the pulmonic valve when moved to
the aortic position.
Mechanical prostheses have proven to be extremely durable and
can be expected to last from 20 to 40 years. However, mechanical
prosthetic valves all require life-long anticoagulation with blood
thinners such as warfarin (Coumadin) to prevent
clot formation on the valve surfaces. Otherwise, blood clots dislodged from these
valves can travel to the brain and cause embolic stroke
or embolic problems in other parts of the body. The original caged-ball Starr-Edwards prosthesis of the 1960s was replaced by the tilting disc Bjork-Shiley
of the 1970s and early 1980s. Although the Bjork-Shiley valve
provided a larger opening for blood flow, a second generation
model of the valve posed the risk of potential breakage resulting
in death, and is no longer available in the United States. The
tilting pivoting disc Hall-Medtronic valve and the two leaflet
(bileaflet) carbon St. Jude valve are commonly used mechanical
prostheses today. These valves provide excellent flow
characteristics but require life-long anticoagulation with blood thinners such
as warfarin (Coumadin), to prevent embolic complications.
The aortic valve area can be opened or enlarged with a balloon
catheter (balloon valvuloplasty) which is introduced in much the
same way as in cardiac catheterization. With balloon valvuloplasty,
the aortic valve area typically increases slightly. Patients with critical aortic stenosis can therefore
experience temporary improvement with this procedure. Unfortunately,
most of these valves narrow over a six to 18 month period.
Therefore, balloon valvuloplasty is useful as a short-term measure to temporarily
relieve symptoms in patients who are not candidates for aortic
valve replacement. Patients who require urgent noncardiac surgery,
such as a hip replacement, may benefit from aortic valvuloplasty
prior to surgery. Valvuloplasty improves heart function and the
chances of surviving non-cardiac surgery. Aortic valvuloplasty can also
be useful as a bridge to aortic valve replacement in the elderly
patient with poorly functioning ventricular muscle. Balloon
valvuloplasty may temporarily improve ventricular muscle function, and thus
improve surgical survival. Those who respond to valvuloplasty
with improvement in ventricular function can be expected to benefit
even more from aortic valve replacement. Aortic valvuloplasty
in these high risk elderly patients has a similar mortality (5%)
and serious complication rate (5%) as aortic valve replacement
in surgical candidates.
- Aortic stenosis is narrowing of the aortic valve,
impeding delivery of blood from the heart to the body.
- 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.
- Echocardiogram and cardiac catheterization are
important tests in diagnosing and evaluating severity of aortic
stenosis.
- 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.
Last Editorial Review: 7/20/2007
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