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Stenosis of Mitral Valve (Mitral Stenosis)

Overview

Mitral stenosis (MS) is a narrowing of the mitral valve opening, the door‑like structure that regulates blood flow from the left atrium to the left ventricle. When the valve is too tight, blood backs up into the lungs, leading to shortness of breath, fatigue, and eventually heart failure if left untreated.

Who it affects

• Most common in adults ages 30‑60.
• Women are affected roughly twice as often as men.
• In developing countries, rheumatic fever remains the leading cause; in high‑income nations, congenital or degenerative causes predominate.

Prevalence

• Globally, rheumatic heart disease accounts for ~1–2% of all cardiac deaths; mitral stenosis represents about 10–15% of rheumatic valve lesions (WHO, 2022).
• In the United States, an estimated 0.1–0.2% of the adult population has moderate‑to‑severe mitral stenosis, most of whom are immigrants from regions where rheumatic fever is endemic (CDC, 2023).

Symptoms

Symptoms often develop gradually and may be mistaken for other respiratory or cardiac conditions. The classic triad includes dyspnea, fatigue, and atrial fibrillation, but many other manifestations can occur.

Cardinal Symptoms

• Shortness of breath (dyspnea) – initially on exertion, later at rest or when lying flat (orthopnea).
• Fatigue & reduced exercise tolerance – due to limited cardiac output.
• Palpitations – most often from atrial fibrillation caused by left‑atrial enlargement.

Additional Symptoms

• Chest discomfort or tightness – usually not classic angina; often a feeling of pressure.
• Cough – dry and worse at night; can be mistaken for asthma.
• Hemoptysis – coughing up small amounts of blood from ruptured pulmonary vessels; a red‑flag sign.
• Swelling of the ankles or feet (peripheral edema) – late sign of right‑sided heart failure.
• Rapid weight gain – from fluid accumulation.
• Decreased appetite & weight loss – secondary to chronic illness.

Causes and Risk Factors

Primary Causes

• Rheumatic fever – an immune reaction to group A streptococcal throat infection; scarring of the leaflets and commissures is the most common cause worldwide.
• Congenital malformations – a small mitral valve or a fused leaflet present at birth.
• Calcific degeneration – especially in older adults; calcium deposits restrict leaflet motion.

Secondary (Less Common) Causes

• Radiation therapy to the chest.
• Systemic lupus erythematosus or rheumatoid arthritis (rare inflammatory involvement).
• Endocarditis leading to leaflet thickening.

Risk Factors

• History of untreated or recurrent streptococcal throat infections.
• Living in or traveling to regions with high rheumatic fever rates (e.g., Sub‑Saharan Africa, South Asia, parts of Eastern Europe).
• Female gender – hormonal and anatomical differences may increase susceptibility.
• Older age – calcific degeneration accumulates over decades.
• Chronic kidney disease – accelerates vascular calcification.

Diagnosis

Accurate diagnosis relies on a combination of clinical assessment and imaging studies.

Physical Examination

• Diastolic rumbling murmur best heard at the apex with the patient in left lateral decubitus.
• Opening snap – a high‑pitched click occurring shortly after S2.
• Signs of atrial fibrillation (irregularly irregular pulse).
• Evidence of pulmonary congestion (crackles on lung auscultation).

Diagnostic Tests

1. Echocardiography (Transthoracic – TTE) – first‑line imaging. Key measurements:
   • Mean mitral valve gradient ≥ 5 mmHg (or >10 mmHg in severe disease).
   • Mitral valve area (MVA) ≤ 2 cm² (≤1.5 cm² = moderate, ≤1.0 cm² = severe).
   • Left‑atrial size, pulmonary artery pressure, and presence of thrombus.
2. Transesophageal echocardiography (TEE) – better visualization of the valve and detection of left‑atrial thrombus, especially before interventions.
3. Cardiac catheterization – rarely needed now, but can directly measure pressure gradients if non‑invasive data are equivocal.
4. Electrocardiogram (ECG) – looks for atrial fibrillation, left‑atrial enlargement, or right‑ventricular strain.
5. Chest X‑ray – may show enlarged left atrium, pulmonary venous congestion, or pleural effusion.
6. Blood tests – CBC (anemia worsens symptoms), renal function, and inflammatory markers if rheumatic activity is suspected.

Treatment Options

Therapy is tailored to disease severity, symptom burden, and patient comorbidities.

Medical Management

• Diuretics (e.g., furosemide) – reduce pulmonary congestion and relieve dyspnea.
• Beta‑blockers or non‑dihydropyridine calcium channel blockers – control heart rate in atrial fibrillation, allowing more filling time.
• Anticoagulation – indicated for atrial fibrillation, prior embolic events, or documented left‑atrial thrombus (warfarin target INR 2.0‑3.0 or DOACs per guidelines).
• Antibiotic prophylaxis – for dental or invasive procedures in patients with prior infective endocarditis or severe mitral stenosis (American Heart Association recommendation).
• Rheumatic fever prevention – long‑term penicillin in patients with a history of rheumatic fever.

Procedural Interventions

1. Percutaneous Balloon Mitral Valvotomy (PBMV)
   • First‑line for pliable, non‑calcified valves (Wilkins score ≤ 8).
   • Success rates 85‑90% for symptomatic relief; low mortality (<1%).
   • Potential complications: mitral regurgitation, atrial septal defect.
2. Surgical Mitral Valve Repair
   • Preferred when valve anatomy is unsuitable for PBMV (heavy calcification, subvalvular fibrosis).
   • Repair (commissurotomy, leaflet thinning) retains native valve and avoids prosthesis‑related issues.
3. Mechanical or Bioprosthetic Mitral Valve Replacement
   • Indicated when repair is impossible.
   • Mechanical valves require lifelong anticoagulation; bioprosthetic valves have limited durability (10‑15 years) but less anticoagulation burden.

Lifestyle & Supportive Measures

• Low‑salt diet (≤ 2 g sodium/day) to limit fluid retention.
• Regular, moderate‑intensity aerobic activity (e.g., brisk walking 30 min most days) as tolerated.
• Avoid heavy lifting or isometric exercises that dramatically increase intrathoracic pressure.
• Vaccinations – flu and pneumococcal vaccines to prevent respiratory infections that can exacerbate heart failure.

Living with Stenosis of Mitral Valve (Mitral Stenosis)

Daily Management Tips

• Weight monitoring – sudden weight gain (>2 kg in 3 days) may signal fluid buildup; report promptly.
• Symptom diary – track dyspnea, palpitations, and activity levels; helps clinicians adjust therapy.
• Medication adherence – set alarms or use pill organizers; missing anticoagulation can be life‑threatening.
• Hydration balance – drink enough fluids to stay hydrated but avoid excess; discuss fluid limits with your cardiologist.
• Dental care – maintain good oral hygiene and inform dentist of your valve disease; prophylactic antibiotics may be required.
• Travel considerations – plan for altitude changes; high altitude can worsen hypoxia and dyspnea.

Psychosocial Support

Living with a chronic heart valve condition can be stressful. Consider these resources:

• Support groups (local hospital or online platforms such as the American Heart Association community).
• Counselling or cognitive‑behavioral therapy for anxiety/depression.
• Cardiac rehabilitation programs that combine exercise with education.

Prevention

Because many cases stem from rheumatic fever, primary and secondary prevention are key.

Primary Prevention of Rheumatic Fever

• Prompt treatment of streptococcal throat infections with appropriate antibiotics (penicillin V or amoxicillin).
• Public health measures: improving living conditions, access to primary care, and school‑based sore‑throat screening in endemic regions.

Secondary Prevention (for patients with a prior rheumatic fever)

• Monthly benzathine penicillin G injections or daily oral prophylaxis for at least 10 years or until age 40 (whichever is longer), per WHO guidelines.

General Cardiovascular Health

• Control hypertension, diabetes, and hyperlipidemia.
• Quit smoking – tobacco accelerates calcific degeneration.
• Maintain a healthy BMI (< 25 kg/m²).

Complications

If mitral stenosis is left untreated, pressure backs up into the pulmonary circulation and the right heart.

• Pulmonary hypertension – elevated pressures can cause right‑ventricular failure.
• Atrial fibrillation – increases the risk of stroke; 30‑40% of MS patients develop AF.
• Thromboembolic events – left‑atrial thrombus can embolize to the brain (stroke), kidneys, or limbs.
• Heart failure – both left‑sided (due to reduced forward flow) and right‑sided (from pulmonary hypertension).
• Endocarditis – damaged valve tissue is a nidus for bacterial infection.
• Pregnancy‑related complications – increased blood volume can precipitate severe decompensation; maternal mortality rises to ~5% without proper management.

When to Seek Emergency Care

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Sources: Mayo Clinic, American Heart Association, CDC, World Health Organization, Cleveland Clinic, National Institutes of Health, European Society of Cardiology Guidelines (2023).

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