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
- Mitral regurgitation murmur: pansystolic (usually high pitched, blowing) murmur best heard at the apex
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
