Mitral stenosis - valve disease

Mitral stenosis

Definition

An abnormal narrowing of the mitral valve.

Incidence

Declining in the Western world due to the decline of rheumatic fever.

Sex

2F : 1M

Aetiology

Almost all mitral stenosis is secondary to rheumatic heart disease; it is also the most common valve to be affected by rheumatic fever. All other causes are rare, but include rheumatoid arthritis, systemic lupus erythematosus and congenital valve narrowing.

Pathophysiology

The pathological process of rheumatic fever results in fibrous scarring and fusion of the valve cusps with calcium deposition. The valve becomes stiff, failing to open fully. When the normal opening of 5 cm2 is reduced to 1 cm2 the mitral stenosis is severe. The pressure within the left atrium rises and left atrial hypertrophy occurs. As a consequence of this the pressure in the pulmonary circulation rises and eventually right atrial pressure will rise leading to right-sided heart failure. The cardiac output falls with little increase possible on exertion.

Clinical features

The condition is asymptomatic until the valve is narrowed by around 50%. The initial symptoms are due to pulmonary venous hypertension and the resultant oedema, with dyspnoea, orthopnoea and paroxysmal nocturnal dyspnoea. Atrial arrhythmias are common and may cause palpatations. A cough productive of frothy, blood-tinged sputum may occur (frank haemoptysis is rare). Progression leads to symptoms of right-sided heart failure (weakness, fatigue and peripheral oedema). On examination the patient may have mitral facies (bi-lateral, dusky cyanotic discoloration of the face). In severe mitral stenosis atrial fibrillation is very common. The apex beat is tapping in nature due to a palpable first heart sound.

On auscultation there is a loud S1 as the mitral valve only closes when the ventricle contracts. There is an opening snap after S2 caused by the stiff mitral valve, followed by a mid to late diastolic rumbling murmur due to turbulent flow through the stenosed valve. If the patient is in sinus rhythm there is a pre-systolic increase in the volume of the murmur due to increased flow during atrial contraction. Pulmonary hypertension may result in pulmonary regurgitation with an early-diastolic murmur (Graham–Steell murmur).

Complications

Complications are frequent:

·        Atrial fibrillation (AF) due to atrial dilation and hypertrophy.

·        Risk of stroke or systemic embolisation with mitral stenosis and AF is high.

·        Pulmonary hypertension and right-sided heart failure.

·        If the stiff valve also fails to close properly, mixed mitral stenosis and regurgitation.

Investigations

Chest X-ray shows selective enlargement of the left atrium (bulge on the left heart border). Calcification within the mitral valve may be visible and there may be signs of pulmonary hypertension and oedema.

In sinus rhythm, the ECG may show a bifid P wave due to delayed left atrial activation; however, atrial fibrillation is common. Signs of right ventricular hyper-trophy such as right axis deviation, right ventricular hypertrophy or right bundle branch block may also be seen.

Echocardiography is diagnostic showing the narrowing and immobility of the valve. Doppler studies can assess the degree of stenosis and any concomitant mi-tral regurgitation. If there is tricuspid regurgitation pulmonary pressures can also be calculated.

Cardiac catheterisation is used if Doppler is inconclusive and to assess for coronary artery disease if valve replacement is contemplated.

Management

The course of mitral stenosis is gradual with intervention based on symptomatology. Associated atrial fibrillation is treated with digoxin and anticoagulation. Cardiac failure may also require treatment. Prophylaxis against infective endocarditis is required. Patients with refractory pulmonary venous congestion or pulmonary hypertension are treated surgically by conservative surgery or valve replacement.