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 prolapse (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)
  • Eventually leads to heart failure

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