Mitral stenosis is almost always rheumatic in origin, although in the elderly it can be caused by heavy calcification of the mitral valve apparatus. There is also a rare form of congenital mitral stenosis.
In rheumatic mitral stenosis, the mitral valve orifice is slowly diminished by progressive fibrosis, calcification of the valve leaflets, and fusion of the cusps and subvalvular apparatus.
The flow of blood from left atrium to left ventricle is restricted
and left atrial pressure rises,
pulmonary venous congestion
Poor lung compliance
There is dilatation and hypertrophy of the left atrium,
left ventricular filling becomes more dependent on left atrial contraction.
Requires increased cardiac output
Increase in heart rate
Diastole shortens when mitral valve is open
Further rise in left atrial pressure
The mitral valve orifice is normally about 5 cm2 in diastole and may be reduced to 1 cm2 or less in severe mitral stenosis.
Patients usually remain asymptomatic until the stenosis is approximately 2 cm2 or less.
At first, symptoms occur only on exercise
In severe stenosis, left atrial pressure is permanently elevated and symptoms may occur at rest.
Reduced lung compliance, due to chronic pulmonary venous congestion, contributes to breathlessness and a low cardiac output may cause fatigue.
Atrial fibrillation due to progressive dilatation of the left atrium is very common. The onset of atrial fibrillation often precipitates pulmonary oedema because the accompanying tachycardia and loss of atrial contraction frequently lead to marked haemodynamic deterioration with a rapid rise in left atrial pressure.
Progressive dilation of left atrium
Tachycardia and loss of atrial contraction
Marked haemodynamic deterioration
Rapid rise in