Mitral Regurgitation

Background and Epidemiology

  • Abnormal reversal of blood flow from the left ventricle to the left atrium
  • Second most common valve disease requiring surgery (after aortic valve)
  • More common in females, low BMI, age

Aetiology/Risk factors

  • Risk factors include
    • previous MI/CAD or infective endocarditis; prior mitral stenosis
    • Following mitral valve surgery
    • Myxomatous degeneration e.g. Mitral valve prolaps(most common and occurs in congenital abnormalities and with age); Ehlers-Danlos syndrome; Marfan’s syndrome
    • Connective tissue diseases e.g. SLE, systemic sclerosis
    • Acute rheumatic fever
    • Cardiomyopathy, congenital heart disease, left ventricular failure (heart failure)

Pathophysiology

  • Chronic mitral regurgitation causes gradual dilatation of the left atrium with little increase in pressure and few symptoms until the atrium can no longer compensate
  • In acute mitral regurgitation and decompensated chronic MR, back pressure builds up in the Left atrium and is transmitted back via the pulmonary vein and can result in pulmonary oedema
  • Chronic decompensated MR eventually proceeds down a similar route as mitral stenosis– as the heart tries to increase stroke volume (as a proportion of stroke volume continues to be regurgitated)

Presentation

  • Many patients are asymptomatic for years
  • Symptoms include
    • Dyspnoea and orthopnoea (pulmonary venous congestion)
    • Fatigue (low cardiac output)
    • Palpitations (atrial fibrillation, increased SV)
    • Oedema
  • Signs
    • Mitral regurgitation murmur: pansystolic (usually high pitched, blowing) murmur best heard at the apex
      • May radiate to the axilla
    • Other heart sound changes include diminished S1, wide splitting of S2 (early closure of aortic valve- low SV); possible prominence of pulmonary component if pulmonary hypertension is present
    • Other signs include displaced heart apex; signs of venous congestion e.g. crepitations

Investigations

  • CXR – heart enlargement
  • ECG- broad P waves and left atrial enlargement (see mitral stenosis)
  • Echocardiography- dilated LA/LV; dynamic LV; structural abnormalities of the mitral valve e.g. prolapse

Management

  • Mild-moderate MR can be treated by managing hypertension and atrial fibrillation if present
  • The mainstay of treatment (particularly in mitral prolapse; symptomatic MR and acute MR) is surgical valve replacement
  • This can be done percutaneously
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