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Mitral Stenosis

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Mitral valve disease, often secondary to rheumatic fever, is treatable with surgery.

Aetiology

The normal cross-sectional area of the mitral valve is 5 cm², but symptoms usually begin when the valve area is reduced to 1-2 cm².
Rheumatic heart disease (RHD) causes scarring and contraction of the valve, leading to a classic "fish-mouth" appearance.
Anticoagulation is recommended if atrial fibrillation (AF), paroxysmal AF (PAF), or a previous cardiac embolus is present.
Progressive scarring and narrowing of the mitral valve can occur due to past episodes of rheumatic fever.

Causes

Common Causes	Details
Rheumatic Heart Disease	Rheumatic heart disease (RHD) is the most common cause of mitral stenosis. It is caused by an immune response to streptococcal infections, leading to long-term inflammation and scarring of the mitral valve.
Congenital Mitral Stenosis	Some individuals are born with a congenital defect that leads to a narrowed mitral valve, often associated with other heart abnormalities.
Mitral Annular Calcification	Calcium deposits in the mitral valve annulus, particularly in elderly patients or those with chronic kidney disease, can cause narrowing of the valve.
Rare Causes	Details
Radiation-Induced Mitral Stenosis	Radiation therapy to the chest can lead to fibrosis of the mitral valve, causing stenosis years after treatment.
Infective Endocarditis	Endocarditis may lead to large vegetations or scarring on the valve leaflets, contributing to mitral stenosis.
Lupus and Autoimmune Diseases	Autoimmune conditions, such as systemic lupus erythematosus (SLE), may cause chronic inflammation and fibrosis of the mitral valve.
Carcinoid Syndrome	Carcinoid tumours can release substances like serotonin, leading to fibrotic changes in heart valves, including the mitral valve.

Clinical Features

Pulse: Atrial fibrillation with low volume and systemic emboli.
Pulmonary edema (not related to left ventricular failure).
Mid-diastolic murmur with presystolic accentuation if in sinus rhythm.
Loud S1 sound with a tapping apex beat due to wide-open valve cusps during systole.
Right ventricular lift and loud P2 sound, indicating pulmonary hypertension.
Ortner’s syndrome: Hoarseness caused by pressure on the left recurrent laryngeal nerve from an enlarged left atrium.
Dysphagia due to an enlarged left atrium pressing on the esophagus.
Left atrial enlargement may compress the left bronchus, leading to bronchiectasis.

Decompensation

Can occur with exercise, emotional stress, or during the second trimester of pregnancy.
Infections or uncontrolled atrial fibrillation can worsen symptoms.

Differential Diagnosis

A left atrial myxoma can mimic mitral stenosis. Myxomas can obstruct the mitral valve during diastole and cause similar symptoms, including a characteristic "tumour plop."

Investigations

Blood Tests: Full blood count (FBC), Urea & Electrolytes (U&E), Liver Function Tests (LFTs), and C-reactive protein (CRP) to rule out infective causes.
ECG: Findings may include atrial fibrillation, P mitrale, right bundle branch block (RBBB), and right ventricular hypertrophy.
CXR: Enlarged left atrium, straight left heart border, pulmonary edema, and enlarged pulmonary artery or right ventricle.
Echocardiogram: Poor leaflet separation during diastole, with calcification and fusion of valve leaflets. Transesophageal echocardiogram (TEE) is the most accurate for evaluating the mitral valve.
Cardiac Catheterization: Used to measure pressure gradients between the left atrium (via PA wedge) and left ventricular end-diastolic pressure (LVEDP), which is usually >15 mmHg in severe cases.

Severity by Valve Area

Normal: 4-6 cm²
Mild: 1.5-2.5 cm²
Moderate: 1-1.5 cm²
Severe: < 1 cm²

Management

Management Strategy	Details
Medical Management	Diuretics: To manage pulmonary congestion and fluid overload. Beta-blockers/Calcium Channel Blockers/Digoxin: To control heart rate, especially in atrial fibrillation. Anticoagulation: Mandatory for patients with atrial fibrillation to prevent thromboembolism. Warfarin or heparin is used; DOACs are contraindicated.
Percutaneous Mitral Balloon Valvotomy (PMBV)	Preferred for symptomatic patients with favorable valve anatomy. A balloon catheter is used to dilate the stenotic mitral valve, restoring normal blood flow. Best suited for younger patients without significant calcification or thickening of the valve.
Surgical Management	Mitral Valve Repair: For less severe valve damage. Mitral Valve Replacement: For severe cases, using either a mechanical or bioprosthetic valve.
Management of Atrial Fibrillation	Rate control with beta-blockers, calcium channel blockers, or digoxin. Rhythm control with antiarrhythmic drugs. Anticoagulation to prevent thromboembolic events.
Lifestyle Modifications	Salt Restriction: To reduce fluid retention and the workload on the heart. Exercise: Mild exercise is encouraged, but strenuous activity should be avoided. Regular Monitoring: Echocardiograms to monitor disease progression and adjust treatment accordingly.

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