What is Aortic Valve Replacement?
Aortic valve replacement is an "open heart"
procedure performed by cardiothoracic surgeons for treatment of narrowing (stenosis)
or leakage (regurgitation) of the aortic valve.
What is the Aortic Valve?
The location of the aortic valve is shown in the
diagram to the left. The heart has two sets of pumping chambers: the
right-sided chambers pump blood to the lungs, and the left side pumps blood
to the rest of the body. The left side, therefore, has a harder job than the
right side, and the left side does most of the work. The main pumping
chambers of the heart are called the ventricles.
Because the ventricle is a pump, it must have
both an inflow valve and an outflow valve. The aortic valve is on the left
side of the heart and is the outflow valve. The aortic valve opens to allow
blood to leave the left ventricle (the main pumping chamber of the heart)
and closes to prevent blood from leaking backwards into the ventricle from
the rest of the body.
What causes the aortic valve to malfunction?
The aortic valve to malfunction for several
reasons. For example, the aortic valve may be abnormal from birth
(congenital aortic valve disease), or it could become diseased with age
(acquired aortic valve disease). The most common congenital abnormality is a
bicuspid aortic valve. As shown below, the aortic valve normally has three
leaflets, but a bicuspid aortic valve has only two. It may, therefore, not
open or close completely.
A bicuspid aortic valve is a common
abnormality and occurs in 1-2% of people. This is the second most common
cause of aortic valve disease requiring surgery. Such valves may function
normally for years before becoming stenotic, regurgitant or both. People
with a bicuspid aortic valve require antibiotic prophylaxis before dental
procedures but generally no other special precautions are required other
than regular follow up with a qualified cardiologist.

Tricuspid (left) and Bicuspid (right) Aortic
Valves
The most common cause of aortic valve disease
requiring surgery is called "senile aortic calcification," meaning that the
valve has worn out with age. When a valve becomes worn, the body deposits
calcium on it for reasons that are unknown. The calcium restricts or limits
the motion of the valve leaflets. This may prevent the valve from opening
(causing stenosis) or closing (causing leakage or regurgitation). Less
common causes of aortic valve disease include diseases of the aorta, the
main blood vessel coming out of the heart and carrying blood to the rest of
the body, including ascending aortic aneurysms, aortic dissection and
Marfan's syndrome.
Are there any warning signs for a failing
aortic valve?
A failing aortic valve may cause a variety of
symptoms including shortness of breath, chest pain (angina pectoris), and
dizziness or loss of consciousness (passing out).
A narrow valve makes the heart work harder
just to pump the blood through the valve to the body. A leaky valve lets
blood back into the heart after it has been pumped out. The heart must
therefore pump more blood forward to make up for the blood that is leaking
backwards. Either way the extra work may cause symptoms of heart failure,
such as shortness of breath. Early on the shortness of breath may be
noticeable only with exercise. Later, with the progression of valve disease,
a patient could experience shortness of breath with even light activity or
at rest. Some patients will be unable to sleep flat in bed or may awaken
from sleep short of breath. Another sign of heart failure that may
occasionally occur is swelling of your feet, particularly prominent later in
the afternoon or evening although other conditions, such as varicose veins,
can also cause this to occur.
The extra work the heart has to perform may
also cause chest pain or angina pectoris similar to the symptoms of a heart
attack. It may be difficult to tell the difference between heart valve
disease and narrowing of the blood vessels to the heart itself (coronary
arteries). Aortic valve disease may also cause dizziness, light headedness
or even fainting spells.
How does someone know if they should have
surgery to repair an aortic valve?
The decision to proceed with surgery should
be made with your medical care team which usually consists of a thoracic or
cardiothoracic surgeon and a cardiologist. Your medical team will likely
base their recommendations on your symptoms and on the results of several
tests including an echocardiogram and sometimes cardiac catheterization. An
echocardiogram may show enlargement of the heart, and can help to measure
the degree of stenosis or regurgitation. A cardiac catheterization provides
similar information, but can also identify any narrowing of the coronary
arteries.
What options exist for the replacement of
artificial valves:
Unlike the mitral valve which can often be
repaired, the aortic valve usually requires replacement. Once the decision
is made to proceed with surgery, choices regarding the type of artificial
valve (prosthesis) used should be considered. In broad terms there are two
types of artificial valves or prostheses: mechanical valves.
Are there differences between mechanical and
biological replacement valves?
A number of excellent mechanical replacement
valves or prostheses are available today. Most surgeons have a particular
preference for one valve over another related to technical factors (how they
are sewn into place), however from the patient's point of view there is
little if any difference between valves. The principle advantage of
mechanical valves is their excellent durability. From a practical
standpoint, they do not wear out. The principle disadvantage is that there
is a tendency for blood to clot on all mechanical valves. Therefore patients
with artificial valves must take anticoagulants or "blood thinners" for the
rest of their life. There is also a small but definite risk of blood clots
causing stroke.
There are a variety of natural or biological valves that can be used to
replace an abnormal valve. They all share a reduced risk of blood clots
forming but all are less durable than mechanical valves. Given enough time,
they will probably all wear out. The options in this category include "xenograft"
valves made from animal tissues (most often pig aortic valves), "humograft"
or "allograft" valves retrieved from human cadavers, and "pulmonary
autograft" valves moved from the patient's pulmonary artery on the right
side of the heart to the aortic position on the left.
The decision on the type of valve used should
be made in conjunction with your cardiothoracic surgeon and your
cardiologist. Ultimately the choice will depend on a patient's preferences,
lifestyle, and individual risks as determined by age and other medical
conditions.
Why is surgery necessary?
The aortic valve is the outflow valve of the
left side of the heart, meaning that it opens during systole (when the
ventricle contracts or squeezes blood out into the aorta and the rest of the
body). When the aortic valve is too narrow or stenotic, the ventricle has to
work harder to pump the blood out to the body. This extra work consumes
significant energy and ultimately requires extra blood flow to the heart
itself. If there is not enough blood flow, the heart becomes ischemic
causing anginal chest pain. Aortic stenosis is often progressive, growing
worse with time. As the valve gets tighter, the heart has to continue to
work harder and harder to keep pumping blood out of the heart. At some point
the heart can no longer compensate, resulting in episodes of low blood
pressure or hypotension or even synocope. As the heart fails to compensate,
fluid will build up in the lungs creating congestion.
When the aortic valve leaks, the heart has to
work harder and similar problem occur. The ventricle must pump more blood
with each contraction to produce the same forward output, creating a
condition called volume overload. The heart can compensate for this volume
overload for many months or years provided the leakage develops slowly.
Eventually, the heart begins to fail producing shortness of breath and
fatigue.
What are the risks of surgery?
Individual risks of surgery can be best
estimated by your cardiothoracic surgeon and cardiologist. Risks generally
depend on age, general health, specific medical conditions, and heart
function.
What will my condition be like after aortic
valve replacement?
After successful aortic valve replacement,
patients can expect to return to their preoperative condition or better.
Anticoagulation ("blood thinners") with a drug like Coumadin may be
prescribed for 6 weeks to 3 months after surgery for those with biological
valves, and for life for those with mechanical valves. Once the wounds have
healed, most patients should experience few if any restrictions to activity.
A patient will require preventative or prophylactic antibiotics whenever
having dental work, and should always tell a doctor about their valve
surgery before any surgical procedure.