Mitral Stenosis

Mitral stenosis is when there is obstruction to flow through the mitral valve separating the left atrium and left ventricle of the heart. The obstruction occurs due to a structural abnormality of the valve.¹

Mitral stenosis increases left atrial and pulmonary arterial pressure (especially in tachycardia). Pulmonary hypertension can lead to right ventricular dilation and tricuspid regurgitation. Right ventricular failure results in raised jugular venous pressure, liver congestion, ascites and peripheral oedema.¹ Left ventricular function and cardiac output can be normal in isolated mitral stenosis. Static blood flow in the left atrium (worsened in atrial fibrillation) can cause thromboemboli.²

There is also a separate article entitled Mitral Valve Disease.

Causes of mitral stenosis include:

• Rheumatic fever - commonest cause
• Degenerative calcification - can occur in the elderly
• Congenital mitral stenosis - secondary to parachute mitral valve or Lutembacher syndrome
• Inborn errors of metabolism - eg Hurler-Scheie syndrome, Fabry disease
• Systemic lupus erythematosus
• Rheumatoid arthritis
• Carcinoid syndrome
• Infective endocarditis with large vegetations
• Amyloid deposition in the mitral valve

Rheumatic fever is triggered by a throat infection with Group A β-haemolytic streptococci. This causes immune damage to the valve 20-40 years later, usually after multiple attacks of acute rheumatic fever. It remains common in Africa, Asia and the Middle East. Acute rheumatic fever is difficult to diagnose and diagnosis of previous infection may have been missed.

This is commonly in the 30s and 40s and may be asymptomatic in the early stages.

• Breathlessness: progressive breathlessness is the main symptom. This can include shortness of breath on exertion, orthopnoea and paroxysmal nocturnal dyspnoea. Pulmonary oedema can be triggered by the onset of atrial fibrillation.
• Atrial fibrillation: palpitations due to atrial fibrillation may be the presenting feature.
• Systemic emboli: is a more rare presentation. Stroke, renal failure and myocardial infarction can occur.
• Haemoptysis: this may occur secondary to rupture of the bronchial veins due to raised left atrial pressure.
• During pregnancy: the increase in blood volume may make a previously asymptomatic woman develop symptoms.

Look for:

• Malar flush on cheeks
• Raised jugular venous pressure
• Laterally displaced apex beat
• Right ventricular heave
• Loud first heart sound with an opening snap in early diastole
• A mid-late diastolic murmur, best heard with patient in the left lateral position with the bell of the stethoscope (there is a separate article entitled Heart Auscultation)
• Atrial fibrillation
• Signs of right ventricular failure including hepatomegaly, ascites and peripheral oedema

• Chest Xray: may show left atrial enlargement and interstitial oedema (Kerly A and B lines) if severe. Mitral valve calcification may be seen. There may be prominent pulmonary vessels with re-distribution of pulmonary vasculature to the upper lobes.¹
• ECG: may reveal atrial fibrillation, left atrial enlargement and right ventricular hypertrophy. (There is a separate article entitled ECG A Methodical Approach.)
• Echocardiography: this is essential to confirm diagnosis (leaflet thickening and restricted movement) and to assess severity.³ It can also look for left atrial thrombus and measure ventricle and atrial sizes. The gradient across the valve and pulmonary artery pressure can be assessed. Transoesophageal echocardiography and exercise echocardiography may also be used.³
• Cardiac catheterisation: this is used less as techniques for echocardiography have improved.

• Pulmonary hypertension
• Dilated left atrium
• Atrial fibrillation
• Thromboembolic events
• Right heart failure
• Infective endocarditis

Treatment aims are to:¹

• Reduce the symptoms of breathlessness and pulmonary congestion
• Control the ventricular rate if atrial fibrillation is present
• Prevent thromboembolic complications
• Ensure adequate prophylaxis against infective endocarditis
• Reduce the recurrence of rheumatic fever

Medical management

• Most asymptomatic patients with mild or moderate mitral stenosis are monitored with annual echocardiograms and clinical examination. They are advised to report symptoms and require infective endocarditis prophylaxis.
• Diuretics ± nitrates can help symptoms of breathlessness.³
• Cardioversion (electrical or pharmacological) can be carried out for recent onset atrial fibrillation. Otherwise, long-term rate control for atrial fibrillation can be achieved with β-blockers, calcium channel blockers or digoxin. There is a separate article entitled Atrial Fibrillation which discusses this.
• Anticoagulation (target INR is 2-3) is recommended if there is:³
  • Atrial fibrillation (permanent or paroxysmal)
  • Left atrial enlargement
  • Thrombus present in the left atrium or a dense spontaneous echo contrast is seen on transoesophageal echo
  • A history of embolism
• β-blockers to reduce heart rate (and trans-mitral gradient) are especially useful during pregnancy, even in sinus rhythm, when clinical tolerance of mitral stenosis is poor.³ They may also be helpful in the non-pregnant state. Heart-rate regulating calcium channel blockers may also be used to slow heart rate and increase exercise tolerance.
• Reducing the recurrence of rheumatic fever: the World Health Organisation recommends that a long-term programme of regular antibiotics to prevent further group A streptococcal infection should be continued lifelong for severe valvular disease and after valve surgery.^4,5
  Intramuscular penicillin is normally used.

Surgical management

Surgical options include:

• Percutaneous balloon valvotomy
• Open mitral valvotomy
• Mitral valve replacement

There is a separate article that discusses surgical treatment for mitral stenosis, the indications for surgery and the surgical results. This is entitled Mitral Valve Operations.

• The 10 year survival rate for asymptomatic people is around 80%.
• The 10 year survival rate for those with mild symptoms is around 60%.
• The 10 year survival rate for those who develop congestive cardiac failure is around 15%.

Recent NICE guidance has brought about a big change in antibiotic prophylaxis for infective endocarditis. NICE advises against routine antibiotic prophylaxis, but recognises patients with valvular heart disease are at increased risk of endocarditis. Such patients should be encouraged to maintain good oral health, should be informed about symptoms that may indicate infective endocarditis (including when to seek expert advice), and the risks of undergoing invasive procedures, particularly non-medical procedures such as body piercing or tattooing.⁶