Mitral valve stenosis

Mitral stenosis (MS) is a structural anomaly of the mitral valve resulting in a decreased cross-sectional area of the valve. The stenosis impairs blood flow from the left atrium to the left ventricle, progressively causing left atrial distension, pulmonary venous congestion, pulmonary hypertension, and congestive heart failure. MS is most commonly a complication of rheumatic fever and is slowly progressive. Patients typically remain asymptomatic for years until the mitral valve area becomes critically reduced. Patients with severe stenosis often present with atrial fibrillation and symptoms of heart failure (dyspnea, fatigue, orthopnea). Asymptomatic patients are initially managed conservatively and the mitral valve is regularly monitored with transthoracic echocardiography. Once symptoms develop or the valve area decreases to 1.5 cm², percutaneous valvuloplasty or surgical intervention may be considered. Occasionally, patients with MS have heart failure secondary to tachycardia or increased cardiac demand and require urgent medical management.

• Most commonly due to rheumatic fever
• Calcification of the mitral valve annulus
• Autoimmune diseases: systemic lupus erythematosus, rheumatoid arthritis
• Congenital
• Some conditions may mimic mitral stenosis: bacterial endocarditis of the mitral valve with large vegetation, left atrial myxoma
• Degenerative aortic stenosis

• Mitral valve stenosis → obstruction of blood flow into the left ventricle (LV) → limited diastolic filling of the LV (↓ end-diastolic LV volume) → decreased stroke volume → decreased cardiac output (forward heart failure)
• Mitral valve stenosis → increase in left atrial pressure → backup of blood into lungs → increased pulmonary capillary pressure → cardiogenic pulmonary edema → pulmonary hypertension → backward heart failure and right ventricular hypertrophy

Symptoms ^[2]

Patients with MS typically progress over many years from being asymptomatic to having symptoms of profound heart failure. Acute symptoms may occur in patients with tachyarrhythmias or an increased cardiac output secondary to pregnancy, sepsis, or exercise.

• Dyspnea
• Fatigue
• Hoarseness
• Dysphagia
• Palpitations
• Symptoms of embolic disease (e.g., stroke, mesenteric ischemia)
• Later stages
  • Symptoms of right heart failure
  • Paroxysmal nocturnal dyspnea
  • Orthopnea
  • Hemoptysis

Examination findings ^[2]

• Mitral facies
• Sequelae of embolic disease (e.g., focal neurologic deficits, cool and cyanotic extremity)
• Irregular heart rhythm secondary to atrial fibrillation
• Clinical features of right heart failure, e.g., lower limb pitting edema , bibasilar rales
• Auscultation (see “Auscultation in valvular defects”)
  • Diastolic murmur heard best at the 5^th left intercostal space at the midclavicular line (the apex)
  • Loud first heart sound (S₁)
  • Opening snap
    • A high frequency, early to middiastolic sound, heard after S₂
    • Occurs when mitral leaflet motion suddenly stops during diastole because the stenosed valve has reached its maximum opening
  • A shorter interval between S₂ and opening snap indicates more severe disease; occurs because left atrial pressure is greater than left ventricular end-diastolic pressure (LVEDP).

Approach ^[1]

• All patients with suspected mitral stenosis should undergo transthoracic echocardiography (TTE).
  • TTE is the best initial test to evaluate the mitral valve and quantify the anatomical extent of the stenosis.
  • Discordance between the patient's symptoms and the echocardiographic classification of the disease should prompt further testing.
• Chest x-ray and ECG may show characteristic changes depending on the stage and extent of disease.
• Laboratory studies are typically nonspecific, although they may support a diagnosis of associated heart failure.

Initial evaluation

Transthoracic echocardiography (TTE) ^[3][4]

• TTE is the most important test for diagnosing and guiding the treatment of mitral stenosis.
• Characteristic findings include:
  • Reduced mitral valve area (MVA): ≤ 1.5 cm² is considered to be severe MS
  • Thickened, calcified leaflets with commissural fusion
  • Increased mean diastolic pressure gradient across the mitral valve
  • Secondary cardiac changes, including:
    • RV dilation
    • LA enlargement
    • Evidence of pulmonary hypertension
• MVA, valve pressure gradient, and presence or absence of symptoms and pulmonary artery hypertension are used to grade the severity of disease.

ECG ^[5]

• Often normal
• Characteristic findings include:
  • Left atrial enlargement/P mitrale
  • Atrial fibrillation
  • Right ventricular hypertrophy (e.g., right axis deviation, dominant R wave in lead V1)

Chest x-ray (PA and lateral views) ^[6]

• Left atrial enlargement
  • The main bronchi appear elevated and have > 90% angulation (splayed).
  • Straightening or convexity of the left cardiac border
  • Double density sign
• X-ray features of pulmonary congestion
• X-ray features of right ventricular enlargement ^[7]

Laboratory tests

• BNP or NT-proBNP: Levels increase in proportion to disease severity. ^[8]
• CBC: Leukocytosis may indicate an underlying infectious (e.g., infective endocarditis) or inflammatory process.
• BMP: may demonstrate evidence of renal impairment ^[9]
• Liver chemistries: may show elevations secondary to congestive hepatopathy
• CRP: suggests ongoing inflammation in rheumatic heart disease ^[10]

Additional evaluation ^[1]

Further studies are indicated in select patients when TTE findings are unclear or do not correlate with symptoms, or when an intervention is planned.

Transesophageal echocardiography (TEE)

• Indicated to confirm the diagnosis if TTE examination is technically suboptimal
• Used prior to intervention to identify:
  • Intracardiac thrombus
  • Significant mitral regurgitation

Stress testing ^[11]

• Useful when symptoms do not correlate with echocardiographic findings, e.g.:
  • TTE shows severe MS but the patient reports no symptoms
  • Patient is symptomatic but TTE shows mild or moderate disease
• Exercise stress testing is preferred over pharmacological stress testing.

Cardiac catheterization

• Indicated if other conditions (e.g., diastolic dysfunction, pulmonary disease) make staging unclear
• Can additionally:
  • Quantify pulmonary hypertension, an important component of the treatment algorithm
  • Identify coronary artery disease prior to planned surgical intervention

Approach ^[1]

The following recommendations are for rheumatic MS. For all other causes of MS, early consultation with cardiology is recommended as treatment can vary significantly.

• Initial management
  • General cardiac care and serial TTEs until signs or symptoms of disease progression occur ^[12]
  • In case of acute heart failure: immediate medical stabilizations and treatment of the precipitating cause
• Indications for interventional management include:
  • Symptomatic MS
  • MVA decreasing to < 1.5 cm²
  • New-onset pulmonary hypertension

Acute stabilization

• Abrupt onset of acute heart failure symptoms in patients with MS is usually secondary to tachycardia or increased cardiac output.
  • Urgent cardiology consultation is recommended.
  • Identify and treat the underlying cause, e.g., sepsis or atrial fibrillation.
• Heart failure symptoms are managed using standard therapy, e.g., diuretics.
• Nitrates may reduce pulmonary congestion but should be used with caution (see “Management of acute heart failure” for further information and dosages). ^[13]

Patients with mitral stenosis often develop acute heart failure following the onset of atrial fibrillation. Rapid and progressive treatment of atrial fibrillation is necessary in patients with severe mitral stenosis.

Conservative management

Many patients with mild to moderate disease can be managed conservatively for years. Patients should remain under the care of cardiology with regular monitoring of valve function.

Serial TTE examinations ^[1]

• Serial TTEs are performed to monitor the progression of MS and guide the timing of interventions.
  • Patients typically do not develop symptoms until they have severe disease.
  • Early detection prevents irreversible cardiac changes.
• Asymptomatic patients
  • Every 3–5 years if MVA is > 1.5 cm²
  • Every 1–2 years if MVA is 1–1.5 cm²
  • Annually if MVA is < 1 cm²
• TTE should be repeated earlier if symptoms develop or change.

Optimizing medical therapy ^[1]

• Patients should receive guideline-directed medical therapy (GDMT) for any concurrent heart failure.
• Screen for and treat all cardiac risk factors, e.g., diabetes, hyperlipidemia, and hypertension.
• Consider heart rate control (e.g., beta blockers) in younger patients in sinus rhythm with high resting or exercise-induced heart rates.
  • Decreasing the heart rate in patients with symptoms of mild to moderate CHF may improve cardiac symptoms.
  • Consider one of the following agents: ^[14]
    • Beta blockers, e.g., metoprolol
    • Ivabradine
• Treat atrial fibrillation with rate control.

Decreased heart rate may also limit cardiac output and cause hypotension; monitor patients carefully.

Anticoagulation

• Anticoagulation with a vitamin K antagonist (VKA) to a target INR of 2.5 is indicated if any of the following are present: ^[1]
  • Atrial fibrillation
  • History of embolic disease
  • Intracardiac thrombus
  • Mechanical prosthetic mitral valve
  • First 3–6 months after bioprosthetic mitral valve implantation
• It is controversial whether anticoagulation is indicated for patients with MS who do not have one of the above features.
• For dosages, see “Anticoagulation in atrial fibrillation”.

Additional measures

• Infectious endocarditis (IE) prophylaxis ^[1]
  • MS alone is not an indication for IE prophylaxis.
  • IE prophylaxis is indicated for dental procedures in high-risk patients (e.g., previous IE) with MS.
  • See “Endocarditis prophylaxis” for antibiotic selection and dosing.
• Management of rheumatic heart disease
  • Patients with acute or recurrent rheumatic fever with cardiac involvement need long-term, daily, antistreptococcal prophylaxis.
  • See “Prevention” in “Rheumatic fever” for further information and dosages.

Interventional management

Patients with severe or symptomatic MS should be considered for intervention.

Indications

• Asymptomatic patients with MVA ≤ 1.5 cm² and either of the following:
  • Pulmonary artery systolic pressure > 50 mm Hg
  • New-onset atrial fibrillation
• Symptomatic patients with:
  • MVA ≤ 1.5 cm²
  • MVA > 1.5 cm² and hemodynamically significant MS on stress test

Procedures

• Percutaneous mitral valve balloon commissurotomy (PMBC) ^[15]
  • PMBC is the preferred intervention in most patients with severe MS.
  • A balloon catheter is advanced percutaneously through the mitral valve and inflated to break open commissural stenosis and increase the mitral valve area. ^[15][16]
  • The Wilkins score is used to determine eligibility.
• Surgery
  • Surgical interventions include open commissurotomy and mitral valve (mechanical or bioprosthetic) replacement.
  • Indications
    • Unfavorable anatomy for PMBC
    • Presence of thrombus in the left atrium
    • Mixed valvular disease (e.g., severe MR, tricuspid disease)
  • Contraindicated if there is a prohibitively high surgical risk

• Atrial fibrillation → thromboembolic events
• Progressive congestion of the lungs, pulmonary edema, pulmonary hypertension
• Congestive heart failure
• Enlarged left atrium (rare) → esophageal compression, recurrent laryngeal nerve palsy

We list the most important complications. The selection is not exhaustive.