Makindo Medical Notes

Related Subjects: | Mitral Regurgitation (Incompetence) | Mitral Stenosis | Mitral Stenosis vs Regurgitation | Mitral Valve Prolapse | Atrial Fibrillation (AF) | Cardiac Valve Replacement | Prosthetic Valves

About Mitral Valve Disease

• Mitral valve disease is most commonly secondary to rheumatic fever and is treatable with surgery, particularly if the mitral valve is severely damaged.

Aetiology (Causes)

• 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 the classic "fish-mouth" appearance of the valve.
• Anticoagulation is recommended for patients with atrial fibrillation (AF), paroxysmal AF (PAF), or a previous cardiac embolus.
• Progressive scarring and narrowing of the mitral valve often occur due to prior episodes of rheumatic fever, contributing to the development of mitral stenosis over time.

Common Causes of Mitral Stenosis

• Rheumatic Heart Disease (RHD): The most common cause of mitral stenosis. It results from 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 congenital defects that lead to a narrowed mitral valve, which is often associated with other heart abnormalities.
• Mitral Annular Calcification: Calcium deposits in the mitral valve annulus, especially in elderly patients or those with chronic kidney disease, can contribute to narrowing of the valve.

Rare Causes

• Radiation-Induced Mitral Stenosis: Previous radiation therapy to the chest can lead to fibrosis and stenosis of the mitral valve many years later.
• Infective Endocarditis: Infections of the heart valves may lead to scarring and thickening of the valve, contributing to mitral stenosis.
• Lupus and Autoimmune Diseases: Chronic inflammation caused by conditions such as systemic lupus erythematosus (SLE) can cause fibrosis of the mitral valve.
• Carcinoid Syndrome: This syndrome, associated with carcinoid tumors, can lead to fibrotic changes in the heart valves, including the mitral valve.

Clinical Features

• Pulse: Atrial fibrillation with a low-volume pulse and potential systemic emboli.
• Pulmonary Edema: This is unrelated to left ventricular failure but due to increased pressure in the left atrium.
• Mid-Diastolic Murmur: A characteristic murmur with presystolic accentuation, particularly when in sinus rhythm.
• Loud S1 Sound: Due to the wide opening of the valve during systole, which leads to a "tapping" apex beat.
• Right Ventricular Lift and Loud P2: Indicating pulmonary hypertension.
• Ortner’s Syndrome: Hoarseness caused by pressure on the left recurrent laryngeal nerve from an enlarged left atrium.
• Dysphagia: Difficulty swallowing, often caused by an enlarged left atrium pressing on the esophagus.
• Bronchiectasis: Caused by compression of the left bronchus due to left atrial enlargement.

A shortened interval between S2 and the opening snap indicates increased left atrial pressure, which is strongly associated with severe mitral stenosis.

Decompensation

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

Differential Diagnosis

• A left atrial myxoma can mimic mitral stenosis. Myxomas may obstruct the mitral valve during diastole, causing symptoms similar to those of mitral stenosis, including a characteristic "tumor plop."

Investigations

• Blood Tests: Full blood count (FBC), Urea & Electrolytes (U&E), Liver Function Tests (LFTs), and C-reactive protein (CRP) to rule out infectious causes.
• ECG: May show atrial fibrillation, P mitrale (bifid P waves), right bundle branch block (RBBB), and signs of right ventricular hypertrophy.
• CXR: Can show an enlarged left atrium, a straightened left heart border, pulmonary edema, and signs of pulmonary hypertension (enlarged pulmonary artery or right ventricle).
• Echocardiogram: Key diagnostic tool. It shows poor leaflet separation during diastole, calcification, and fusion of the valve leaflets. A transesophageal echocardiogram (TEE) is the most accurate for evaluating the mitral valve.
• Cardiac Catheterization: Measures pressure gradients between the left atrium 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

• Medical Management: Diuretics are used to manage pulmonary congestion and fluid overload. Beta-blockers, calcium channel blockers, or digoxin can be used to control heart rate, particularly in atrial fibrillation.
• Anticoagulation therapy is mandatory for patients with atrial fibrillation to prevent thromboembolism. Warfarin or heparin is commonly used, as DOACs are contraindicated in mitral stenosis with atrial fibrillation.
• Percutaneous Mitral Balloon Valvotomy (PMBV): This is the preferred treatment for symptomatic patients with favorable valve anatomy, especially those with minimal calcification or thickening of the valve.
• Surgical Management: In more severe cases, mitral valve repair or replacement is necessary. For less severe valve damage, repair is preferred, while for severe cases, replacement with a mechanical or bioprosthetic valve is performed.
• Management of Atrial Fibrillation: Rate control with beta-blockers or calcium channel blockers is essential. Antiarrhythmic drugs can be used for rhythm control, and anticoagulation is required to prevent thromboembolic events.
• Lifestyle Modifications: Salt restriction is advised to reduce fluid retention. Mild exercise can be encouraged, but strenuous activities should be avoided. Regular monitoring through echocardiograms is essential to assess disease progression and modify treatment accordingly.