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