* MITRAL STENOSIS
Normal mitral valve orifice in adult is 4-6 cm2.
Significant flow obstruction occurs when it is <2 cm2. When it
is reduced to 1 cm2, a left atrial pressure of about 25 mmHg is required
to maintain a normal CO. The elevated atrial pressure will raise pulm venous
& capillary pressures, reducing pulm compliance & causing exertional
Dyspnea, pulm edema, atrial arrhythmias, hemoptysis from rupture of
pulm-bronchial venous connections secondary to pulm venous hypertension.
Right vent.failure, fatigue, abd.discomfort of hepatic congestion.
Recurrent pulm. emboli or infarction. Pulm. infections, infective
a rumbling diastolic murmur at the apex, esp. with the patient lie on the
left side and by using provocative maneuvers such as exercise to increase
the heart rate.
ECG: may reveal left atrial enlargement.
Chest x-ray: Left atrial enlargement, mitral valve calcification, and signs
of pulmonary congestion .
Doppler echocardiography is the test of choice in confirming the
diagnosis, establishing the severity of stenosis, detecting complications,
and determining the most appropriate intervention (provided intervention
Echocardiography also allows accurate differentiation of mitral stenosis
from a left atrial myxoma. The severity of stenosis is determined by
measuring the pressure gradient across the valve with Doppler echocardiography
and by calculating the valvular area. Mitral stenosis should be suspected
if the mean gradient exceeds 5 mm Hg; the pressure can exceed 20 mm Hg in
Prophylaxis for infective endocarditis.
Dietary salt restriction, diuretics, control vent. rate (esp. with
atrial fibrillation/flutter) with B-blockers , Calcium blockers or digoxin.
Anticoagulation with warfarin is indicated to prevent thromboembolism
when (1) atrial fibrillation is present, (2) there is a history of embolism,
or (3) the left atrium is large (> 50 mm in diameter on echocardiography).
Mitral valvulotomy is indicated in symptomatic pt with
pure MS whose effective orifice is < 1.3 cm2 (or 0.8 cm2/m2 of body surface
Mitral valve replacement in those with critical MS of <1.0 cm2,
and in NYHA class III.
Bioprosthesis has less thromboembolic complications, does not need permanent
anticoagulation, but may need repeat replacement in 30% of pts in 10 yrs,
and in 50% of pts in 15 yrs; not suitable for young pts < 35 yo.
Mechanical prosthesis needs permanent anticoagulation to prevent
thromboembolism, but lasts longer.
Scientific American Medicine 1999
Caring for patients with prosthetic heart valves
J of Med Jan. 2002