Mitral Valve Surgery
The mitral valve
is a one-way valve that prevents backflow of blood from the left ventricle
(main pumping chamber of the heart) to the left atrium (collecting chamber
receiving blood from the lungs). The valve may malfunction in two possible
ways: it may become leaky (mitral insufficiency or regurgitation) or
it may become obstructed or blocked (mitral stenosis). Ineither case,
blood backs up into the blood vessels of the lungs causing severe shortness
of breath and heart failure. The causes range from rheumatic heart disease
to heart attack (damaging the structure or function of the mitral valve)
to infection. Also, any condition that causes the heart to dilate to
a large size can cause mitral insufficiency. If the mitral valve abnormality
becomes severe enough, symptoms will develop and become worse over time,
sometimes leading to irreversable damage to the heart and lungs. Mitral
valve diseases should be treated with medications in combination with
surgical replacement or repair in select circumstances. 
The
mitral valve can be replaced with two types of valves: mechanical or
tissue. The tissue valve seen at right can come from either a pig valve
or made from the pericardium (sac surrounding the heart) of cattle.
The advantage of the tissue valve is that long-term anticoagulation
(blood thinning) may not be necessary. Its major disadvantage is that
tissue valves tend to develop structural deterioration and malfunction
more quickly than mechanical valves. This may lead after a few years
to the need for repeat mitral valve replacement, a procedure that can
carry more risks than the initial valve surgery. 
A mechanical valve (seen at left) can be used to replace the malfunctioning
mitral valve. The advantage of this valve is that the long-term durability
of the valve is greater than the tissue valve. The likelihood of structural
deterioration is small. However, life-long anticoagulation is required
when this type of valve is used. This may lead to both minor and major
bleeding complications over time. Additionally, there is a risk of blood
clot formation on the valve should the blood not be thinned enough.
The surgeon and cardiologist should discuss with the patient the options
for valve replacement prior to surgery. 
In
most cases the abnormal mitral valve can be repaired rather than replaced.
At right one can see the finished result after one of the most common
types of mitral valve repair. In this case a portion of one of the valve
leaflets was abnormal and therefore cut away. The remainder of the valve
was reattached or reconstructed, and a supporting ring was sutured around
the mitral valve annulus or hinge-points of the valve leaflets. This
is known as a ring annuloplasty. To view an echocardiogram of the mitral
valve before and after this type of repair, click here.