Mitral Valve Disease
By Bruce T. Liang, M.D., F.A.C.C.
The valves of the heart work like flaps to keep blood flowing
in a one-way direction. The mitral valve connects the left
atrium to the left ventricle. Normally, it opens to let blood
flow from the left atrium to the left ventricle and then closes
when the left ventricle contracts, sending blood out of the left
ventricle through the aorta to the rest of the body.
When the mitral valve fails to close properly during the
contraction of the ventricle, a condition known as mitral
regurgitation occurs. In this condition, blood flows or leaks
back into the left atrium causing pressure in the lungs that can
result in congestion and the symptoms of shortness of breath and
easy fatigue.
Coronary artery disease can cause a form of mitral
regurgitation, known as ischemic mitral regurgitation. This
usually results from the stretching or displacement of the
papillary muscle that holds the valve to the ventricle.
Generally, coronary bypass surgery or angioplasty does not
correct ischemic mitral regurgitation. Valve repair or
replacement is needed. Surgeons and anesthesiologists caring for
patients with ischemic regurgitation in the operating room
should be aware that the severity of regurgitation may become
deceptively modest during administration of anesthesia.
Timing of Surgery
The following categories can help determine the optimal timing
of surgery for patients with mitral valve disease.
Category 1: Asymptomatic and normal left ventricular
function. Surgical repair of the mitral valve is recommended
in asymptomatic patients with normal left ventricular function
if the repair can be guaranteed or nearly guaranteed.
Category 2: Symptomatic but normal left ventricular
function. The presence of any symptoms in patients with
severe mitral regurgitation will be an indication for surgery.
The physician needs to be aware of patients who mask symptoms by
subconsciously or consciously curtailing the level of their
physical activity and altering their lifestyle.
Category 3: Asymptomatic but with abnormal left
ventricular function. Once again, the physician needs to be
aware of patients who alter their lifestyle to mask symptoms. An
exercise test or sequential exercise test in patients with
mitral regurgitation can be helpful detecting a change in
exercise capacity. Serial echocardiograms measuring the left
ventricular ejection fraction (that is, the amount of blood
pumped out of the ventricle with each beat) are very helpful.
For example, if the ejection fraction falls below 60% or left
ventricular end systolic dimension increases above 45 mm, then
it is time to consider surgery, before left ventricular function
deteriorates further
Category 4: Symptomatic and with advance left ventricular
dysfunction. Surgical repair for primary valvular disease
may still be beneficial even if the ejection fraction is in the
abnormal range. Otherwise medical therapy with diuretics,
anticoagulation, and control of atrial fibrillation, is
recommended. |
