Monday, March 26, 2012

Mitral Regurgitation (MR)

Mitral Regurgitation

Etiology
  • Rheumatic heart disease (most common cause).
  • Mitral valve prolapse.
  • Chronic left ventricular failure with dilatation of the mitral valve ring may cause functional mitral regurgitation.
  • Connective tissue disorders e.g. SLE, rheumatoid arthritis.
  • Hypertrophic cardiomyopathy.
  • Collagen abnormalities such as Marfan’s syndrome, Ehlers-Danlos syndrome.
  • Acute MR may occur due to rupture of chordae tendineae a complication of infective endocarditis or rupture of papillary muscles due to myocardial infarction.

Pathology
  • Regurgitation of blood from left ventricle to the atrium occurs throughout systole. During diastole, regurgitant blood flows back across the mitral valve. Left ventricular volume is greatly increased, being the sum of cardiac output plus the regurgitant flow; the left ventricle is thus dilated and hypertrophied.
  • The left atrium, which accepts both the pulmonary venous return and regurgitent flow is also dilated in chronic cases. Left arterial pressure and pulmonary venous pressure are increased. In chronic ases, there is pulmonary fibrosis, pulmonary arterial hypertension and right ventricular hypertrophy followed by failure. Acute mitral valve regurgitation produces pulmonary edema and acute left heart failure.

Clinical Features
  • Features of left heart failure such as exertional dyspnea.
  • Palpitation due to atrial fibrillation.
  • On auscultation there is soft first heart sound, a loud third heart sound and pansystolic murmur at apex.

Investigation

X-ray Chest: This shows cardiomegaly due to left atrial and left ventricular enlargement. Pulmonary hypertension may be evident, pulmonary edema and pleural effusion in case of heart failure.

ECG
  • Bifid P wave due to left atrial hypertrophy
  • Left ventricular hypertrophy occurring in about 50% of cases and manifests as:
  • Right ventricular enlargement in some patients.

Echocardiography
This shows dilated left atrium and left ventricle. It confirms the diagnosis of mitral regurgitation. Severity of Mitral Regurgitation can also be assessed.

Management
Medial treatment in mild to moderate cases. Mitral valve repair or replacement in severe cases.

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