Mitral Valve Disease: Mitral Stenosis

Topics: Heart, Cardiology, Mitral stenosis Pages: 7 (1175 words) Published: January 5, 2014
MITRAL VALVE DISEASE

MITRAL STENOSIS

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

and breathlessness.

There is dilatation and hypertrophy of the left atrium,

left ventricular filling becomes more dependent on left atrial contraction.

Exercise, pregnancy

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.

Clinical features

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

Atrial fibrillation

Tachycardia and loss of atrial contraction

Marked haemodynamic deterioration

Rapid rise in left atrial pressure

Pulmonary venous congestion

Pulmonary edema

In contrast, a more gradual rise in left atrial pressure tends to cause an increase in pulmonary vascular resistance, which leads to pulmonary artery hypertension that may protect the patient from pulmonary oedema. Pulmonary hypertension may lead to right ventricular hypertrophy and dilatation, tricuspid regurgitation and right heart failure.

Less than 20% of patients remain in sinus rhythm; many of these have a small fibrotic left atrium and severe pulmonary hypertension.

All patients with mitral stenosis, and particularly those with atrial fibrillation, are at risk from left atrial thrombosis and systemic thromboembolism. Prior to the advent of anticoagulant therapy, emboli caused one-quarter of all deaths in this condition.

CLINICAL FEATURES OF MITRAL STENOSIS

Breathlessness (pulmonary congestion)
Fatigue (low cardiac output)
Oedema, ascites (right heart failure)
Palpitation (atrial fibrillation)
Haemoptysis (pulmonary congestion, pulmonary embolism)
Cough (pulmonary congestion)
Chest pain (pulmonary hypertension)
Symptoms of thromboembolic complications (e.g. stroke, ischaemic limb)

Signs

Loud first heart sound, opening snap
Atrial fibrillation
Mitral facies
Mid-diastolic murmur
Auscultation
RV heave, loud P2
Crepitations, pulmonary oedema, effusions
Signs of raised pulmonary capillary pressure
Signs of pulmonary hypertension

Effort-related dyspnoea is usually the dominant symptom.
Exercise tolerance typically diminishes very slowly over many years and patients often do not appreciate the extent of their disability. Eventually symptoms occur at rest.
Acute pulmonary oedema or pulmonary hypertension can lead to haemoptysis. Systemic embolism may be a presenting feature.

Signs

The forces that open and close the mitral valve increase as left atrial pressure rises. The first heart sound (S1) is...
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