Mitral Stenosis

Mitral stenosis is a valvular heart disease characterised by the narrowing of the mitral valve opening, typically caused by rheumatic heart disease.

The normal mitral valve area is about 4-6 cm², and any reduction below 2 cm² can lead to significant clinical effects. Early diagnosis is very important, especially in pregnancy, to manage the increased cardiac output demand.

Signs and Symptoms

Mitral stenosis typically presents with symptoms of heart failure, such as dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea (PND). Patients may also experience palpitations, chest pain, hemoptysis, and thromboembolism in later stages due to increased left atrial volume and the risk of atrial fibrillation. Signs of right-sided heart failure, including ascites, oedema, and hepatomegaly, may also be present.

Natural History

The progression of mitral stenosis secondary to rheumatic fever generally involves a long latent phase averaging 16.3 ± 5.2 years. Once symptoms begin, progression to severe disability occurs over the next 9.2 ± 4.3 years. If left untreated, survival rates at 5 and 10 years are 44 ± 6% and 32 ± 8% respectively.

Cause

Rheumatic heart disease, a sequela of rheumatic fever, is the primary cause of mitral stenosis. Other rare causes include mitral valve calcification, congenital heart disease, infective endocarditis, and various systemic illnesses like systemic lupus erythematosus and amyloidosis.

Pathophysiology

The normal mitral valve opens during left ventricular diastole to allow blood to flow from the left atrium to the left ventricle. Mitral stenosis causes a pressure gradient across the valve, leading to increased left atrial pressure and, subsequently, pulmonary congestion and pulmonary hypertension. Over time, the left atrium dilates, increasing the risk of atrial fibrillation and systemic embolisation.

Diagnosis

Physical Examination

Auscultation in mitral stenosis often reveals a loud first heart sound, an opening snap following the aortic component of the second heart sound (A2), and a mid-diastolic rumbling murmur best heard at the apex. Signs of right-sided heart failure may also be present.

Echocardiography

Echocardiography is the most definitive diagnostic tool, showing left atrial enlargement, thickened and calcified mitral valve, and signs of right ventricular failure. The trans-mitral gradient measured by Doppler echocardiography is the gold standard for assessing severity.

Other Techniques

Chest X-ray and electrocardiography can provide additional diagnostic information. Cardiac catheterisation can measure pressure gradients between the left atrium and ventricle, although it may overestimate severity.

Treatment

Treatment is unnecessary for asymptomatic patients. In symptomatic cases, options include mitral valve replacement and percutaneous mitral valvuloplasty. Balloon dilatation is another minimally invasive option, especially for those with a favourable score based on echocardiographic criteria.

Mitral Valvuloplasty

This procedure involves dilating the mitral valve using a balloon catheter. It is associated with good success rates and low complications if patients are carefully selected. However, long-term follow-up is necessary to detect restenosis.

In addition to these interventions, concomitant conditions like angina, hypertension, and heart failure should be treated according to standard protocols.

Mitral stenosis is a complex condition requiring careful diagnosis and management to prevent serious complications and improve patient outcomes.

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Self-assessment MCQs (single best answer)

What is the normal mitral valve area?

What is the primary cause of mitral stenosis?

Which symptom is NOT typically associated with mitral stenosis?

What is the gold standard for assessing the severity of mitral stenosis?

Which heart sound is often loud in mitral stenosis?

What is the treatment of choice for symptomatic mitral stenosis with favourable anatomy?

What does the opening snap following the aortic component of the second heart sound (A2) indicate?

Which of the following is a common late complication of mitral stenosis?

What is the typical progression time from symptom onset to severe disability in mitral stenosis?

Which is NOT a sign of right-sided heart failure associated with mitral stenosis?