Mitral stenosis: Causes, Symptoms, Diagnosis and Treatment

Mitral stenosis is  a valvular heart disease most commonly caused by Rheumatic fever. Pure Mitral stenosis occurs in 40% of all patients with rheumatic fever and the remaining 60% have MS accompanied by other valvular heart disorders like mitral regurgitation (MR) and aortic valve diseases. The incidence of Mitral Stenosis has declined in the last decade due to considerable reduction in acute rheumatic fever , especially in middle to high income countries. However, it is common in low-income countries, especially in sub-saharan Africa, India, Southeast asia and Oceania.

Mitral Stenosis causes

1. Rheumatic fever
2. Age related calcifications
3. Radiation induced
4. Congenital ( Parachute valve)
5. SLE, rheumatoid arthritis
6. Myxoma
7. Infectious Endocarditis with large vegetations
8. Severe mitral annular calcifications with leaflet involvement

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Rheumatic Mitral Stenosis

It causes diffuse thickening of the valve leaflets with the formation of fibrous tissue with calcific deposits which leads to fusion of mitral commissures and chordae tendinae. It further causes rigidity of the valvular cusps and eventual narrowing at the apex of the funnel shaped valve. This maybe exacerbated by inflammation, fibrosis and trauma to the valve due to altered flow patterns. Thrombosis and embolization may occur from the calcific valve. Calcification of the stenosed valves impair the mobility of the leaflets.

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Mitral stenosis symptoms

1. Dyspnea
2. Orthopnea
3. Paroxysmal Nocturnal dyspnea
4. Hemoptysis
5. Atrial Fibrillation
6. Systemic thromboembolism
7. Voice hoarseness from recurrent laryngeal nerve compression due to Left Atrial Enlargement ( Ortner syndrome)

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Physical examination findings

1. Mitral facies( Pinkish purple patch on the skin)
2. Loud S1, Loud P2 if pulmonary hypertension
3. Closely split S2 due to accentuation of P2
4. Opening snap
5. Mid diastolic rumble

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Mitral Stenosis pathophysiology

• Normal area of mitral valve orifice is 4-6 cm sq. And significant obstruction i.e orifice area <= 2 cm sq causes flow of blood from left atrium to the left ventricle only if there is abnormally elevated left atriovenrticular pressure gradient which occurs in MS>
• Severe obstruction requires high strial pressure of 25mm Hg to maintain normal cardiac output.
• Anything that increases blood flow to the mitral valve precipitates dyspnea.
• An increase in heart rate shortens diastole more than the systole and diminishes the time available for flow across the mitral valve. At any CO, tachycardia increases the transvalvular pressure gradient and further elevates the Left atrial pressure.
• LV diastolic pressure and EF are normal in MS.
• Pulmonary hypertension can occur due to
• Passive backward transmission of elevated LA pressure.
• Pulmonary arterial Hypertension
• Obliterative changes in pulmonary vascular bed.

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Mitral stenosis diagnosis

Chest Xray

• Pulmonary blood flow redistribution to upper lobes.
• Dilated pulmonary vessels
• Left atrial enlargement
• Flattened left heart border

ECG

• P mitrale ( Broad and notched P waves)
• Atrial tachyarrythmias
• Right ventricular hypertrophy ( tall R waves in V1 and V2)

Transthoracic Echocardiography

• Mitral Valve thickening/calcification
• Decreased mobility of mitral valve, Coexisiting MR

Cardiac Catheterization

• It can be useful when there is discrepancy between clinical and non invasive findings.
• It can help assess associated lesions such as AS, AR.
• It can be helpful in patients with worsening or recurring symptoms after mitral valve intervention.

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Mitral stenosis treatment

Mitral balloon commissurotomy

Done in symptomatic patients with isolated severe MS , whose effective orifice is < 1 cm sq. Per metre sq. Body surface area. It can be done percutaneously or surgically.

Percutaneous Balloon Commisurotomy

It is ideally done in patients with-

• Relatively pliable leaflets with little or no calcifications
• No LA thrombosis
• No significant scarring

Surgical Balloon Commissurotomy

Done in patients in whom PMBS is not possible or unsuccessful or in those with restenosis.

Mitral valve replacement

• It is necessary in patients with MS and significant associated MR
• Anticoagulants like Vitamin K antagonist- warfarin are administered in MS to patients who have AF, a history of thromboembolism.

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