Mitral Stenosis

Background and Epidemiology

  • Obstruction of the flow of blood into the left ventricle during diastole due to structural abnormality of the mitral valve
  • Rare in developed countries (<1 in 100,000) as the majority is secondary to rheumatic heart disease

Aetiology/Risk factors

  • Rheumatic fever (most common)
  • Degenerative calcification (occurs occasionally with age)
  • Connective tissue diseases e.g. rheumatoid arthritis, SLE
  • Infective endocarditis (severe disease)
  • Rare congenital causes e.g parachute mitral valve, lutembacher’s syndrome, Anderson-Fabry disease

Pathophysiology

  • Narrowing of the mitral opening results in back pressure on the left atrium (causing dilation and hypertrophy) and pulmonary veins.  Ventricular filling becomes dependent on atrial contraction (instead of a passive process).
    • subsequent pulmonary hypertension and right heart strain (right ventricular hypertrophy and possibly right heart failure)
      • Effects on the L atrium can lead to AF

Presentation

  • History/symptoms
    • Exertional dyspnoea usually develops slowly and shortness of breath can eventually occur at rest.
      • Patients may also have orthopnoea and/or paroxysmal nocturnal dyspnoea
    • Fatigue is common (due to decreased cardiac output)
    • Oedema
    • Cough, haemoptysis (can be due to pulmonary oedema or due to pulmonary embolus secondary to right heart dysfunction)
    • Chest pain
    • AF- palpitations; thromboembolic disease (rare to be presenting complaint but very possible e.g. stroke, ischaemic limb)
  • Examination/signs
    • Malar flush (mitral facies) on the cheeks- usually indicative of chronic/severe disease
    • Raised JVP (raised atrial pressure and potentially subsequent tricuspid regurgitation)
    • Laterally displaced apex beat (hypertrophy/dilatation); parasternal heave (right ventricular enlargement)
    • Loud 1st heart sound (snap) or diminished 1st heart sound (late disease); split second heart sound
    • Mid-late diastolic murmur (mitral stenosis)- low pitch, best heard with the bell in the mitral area/axillary line with the patient leaning on the left side.  Increases in intensity at late-diastole (with atrial contraction)
      • Other murmers e.g. pulmonary regurgitation (high pitched descrescendo murmur in the pulmonary area) may be heard (consequence of pulmonary hypertension); tricuspid regurgitation (pansystolic murmur secondary to R ventricular dilatation); as well as co-existant mitral regurgitation (pansystolic murmur radiates to the axilla)

Investigations

  • CXR – may show enlarged heart and pulmonary oedema (Kerley lines)
  • ECG
    • AF
    • Right ventricular enlargement
      • Right axis deviation of +110° or more.
      • Dominant R wave in V1 (> 7mm tall or R/S ratio > 1).
      • Dominant S wave in V5 or V6 (> 7mm deep or R/S ratio < 1).
      • QRS duration < 120ms (i.e. changes not due to RBBB).
    • Left atrial enlargement
      • In lead II
        • Bifid P wave with > 40 ms between the two peaks
        • Total P wave duration > 110 ms
      • In V1
        • Biphasic P wave with terminal negative portion > 40 ms duration
        • Biphasic P wave with terminal negative portion > 1mm deep
  • Echocardiography
    • Thickened, immobile cusps; reduced valve area
    • Enlarged L atrium
    • Reduced rate of L ventricular filling

Management

  • If the patient is in AF, manage this accordingly with anticoagulation
  • If the patient is asymptomatic, follow up echocardiography and supportive management is all that is required
  • Medical management for symptoms (breathlessness).  NB Depending on the severity, it may be more appropriate for valvulotomy first line
    • Diuretics or long-acting nitrates
    • Beta-blockers or rate-limiting calcium channel blockers can also improve exertional dyspnoea and may also reduce risk of AF
  • Surgery
    • Percutaneous mitral commissurotomy (valvulotomy)
      • NB contraindicated if the patient also has moderate-severe mitral regurgitation, or other valvular disease (aortic, tricuspid mainly); coronary heart disease; left atrial thrombus

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