|
Mitral Valve Surgery
Mitral valve repair is an open heart procedure performed by cardiothoracic
surgeons to treat stenosis (narrowing) or regurgitation (leakage) of
the mitral valve.  The mitral valve is the "inflow valve" for
the left side of the heart. Blood flows from the lungs, where it picks
up oxygen, and into the heart through the mitral valve. When it opens,
the mitral valve allows blood to flow into the heart's main pumping chamber
called the left ventricle. It then closes to keep blood from leaking
back into the lungs when the ventricle contracts (squeezes) to push blood
out to the body. It has two flaps, or leaflets.
The mitral valve is highlighted on this illustration of a heart. The
mitral valve is the "inflow valve" for the left side of the
heart. Blood flows from the lungs, where it picks up oxygen, and into
the heart through the mitral valve.
Occasionally, the mitral valve is abnormal from birth (congenital). More often
the mitral valve becomes abnormal with age (degenerative) or as a result of
rheumatic fever. In rare instances the mitral valve can be destroyed by infection
or a bacterial endocarditis. Mitral regurgitation may also occur as a result
of ischemic heart disease (coronary artery disease). 
When a normal vlave opens (left), the mitral valve allows blood to flow into
the heart's main pumping chamber called the left ventricle. It then closes
(right) to keep blood from leaking back into the lungs when the ventricle contracts
(squeezes) to push blood out to the body. It has two flaps, or leaflets.
Often the mitral valve is so damaged that it must be replaced (refer to Mitral
Valve Replacement). Occasionally, however, the valve can be repaired rather
than replaced. One type of repair is a procedure called mitral commisurotomy.
Mitral commisurotomy can be performed for some valves that are narrow or "stenotic" either
from birth or from damage by rheumatic fever. Most often today, rheumatic mitral
stenosis is treated by balloon valvuloplasty, a procedure performed in the
cardiac catheterization laboratory by interventional cardiologists. Using a
catheter with a balloon on the end, the balloon is expanded inside the valve "stretching" it
open.
More often mitral valve repair is performed to correct a leaking or regurgitant
valve. Congenital mitral regurgitation may be due to a cleft mitral valve (a
valve with a separation or cleft down the middle) associated with an atrial
septal defect, a type of hole in the heart between the low pressure chambers
or atria. Such valves can sometimes be repaired simply by closing the cleft
with sutures. Valves regurgitant due to bacterial endocarditis can occasionally
be repaired, however the majority of mitral valve repairs are performed for
degenerative disease.  Degenerative
mitral valve disease may be due to an elongation or rupture of the chordal
apparatus, the "heart-strings" that support
the valve normally, or due to a more generalized weakness of the valve itself
such as the "floppy valve" syndrome in which all of the components
of the valve are enlarged and elongated. (Degenerative mitral prolapse right
- note floppy and redundant middle posterior leaflet, one of the most common
mitral valve conditions).
Not all mitral valves can be repaired. A preoperative echocardiogram may help
your surgeon predict the likelihood of repair, but cannot guarantee it. Mitral
valves that are regurgitant due to rheumatic fever are often both stenotic
and regurgitant, and are often beyond repair.
WHY IS SURGERY NECESSARY?
The mitral valve is the inflow valve into the left side of the heart. It closes
during systole (when the ventricle contracts or squeezes blood out into the
aorta and the rest of the body). When the mitral valve leaks, blood flows backwards
into the lungs. The ventricle must therefore pump more blood with each contraction
to produce the same forward output of blood throughout the body. This resulting
condition is called a volume overload. The heart can compensate for this volume
overload for many months or years (provided the leakage came on slowly and
progressively), but it eventually begins to fail producing symptoms of shortness
of breath or fatigue.
WHEN IS SURGERY NECESSARY?
The indications for mitral valve repair are undergoing constant re-evaluation.
Recent evidence suggests that earlier surgical intervention, particularly if
repair is possible, may prevent irreversible damage to the heart. The decision
regarding when to proceed with surgery should be made with your doctor. This
decision will require judgment regarding the risk of surgery and the benefits
available from surgery. In some cases blood pressure medications, such as ACE-inhibitors
can significantly relieve symptoms.
Severe mitral regurgitation in the presence of symptoms of congestive heart
failure is usually an indication for surgery. Severe regurgitation diagnosed
by echocardiography, even without symptoms, may be sufficient to warrant repair.
Enlargement of the left atrium, particularly in the setting of the recent onset
of an irregular heartbeat (atrial fibrillation, premature atrial contractions,
paroxysmal atrial tachycardia, etc.) is considered by many doctors also to
be an indication for surgery.
WHAT ARE THE RESULTS OF MITRAL VALVE REPAIR
The first thing to remember is that a surgeon can predict the likelihood of
repair before surgery, but cannot guarantee it. If repair is possible, the
likelihood of long-term success is good, particularly for degenerative valve
disease.  Depending upon the underlying abnormality there may be an 85 to
95% chance of needing nothing further done to the valve over the next 10
years. If a more complex repair was required for degenerative disease, the
chances of long-term freedom from reintervention (further surgery) may be
less. If a valve was damaged by rheumatic fever, the disease may progress
even after the repair, making the chances of the repair holding up in the
long run less. Some surgeons are, therefore, reluctant to repair rheumatic
valves.  The results of repair of mitral regurgitation associated with coronary
artery disease are the most difficult of all to predict.
WHAT WILL MY CONDITION BE LIKE AFTER MITRAL VALVE REPLACEMENT?
After successful mitral valve replacement you can expect to return to your
preoperative condition or better. Anticoagulation (blood thinners) with Coumadin
is often prescribed for 6 weeks to 3 months postoperatively. Generally this
prescription is not required in the long term unless other indications for
anticoagulation such as atrial fibrillation are present. Once wounds have healed
there should be few if any restrictions on a patient's activity. (For more
information about your recovery, refer to What to Expect After Your Heart Surgery.)
You will require prophylactic antibiotics as a preventive measure against
infection whenever you have dental work done. Always tell your doctor or dentist
that you have had valve surgery before any surgical procedure.
Thoralf Sundt for Society of Thoracic Surgeons (2000)
|
