acute mitral regurgitation (MR)

Etiology

• papillary muscle dysfunction or rupture due to myocardial ischemia or myocardial infarction
  • inferior wall & inferior-posterior wall MI most common
• rupture of a chorda tendoneae (most common)
• infective endocarditis with flail or perforated leaflets
• severe myxomatous disease
• flail mitral leaflet
• trauma

Pathology

• compensatory increases in left ventricular & left atrial compliance are not present
• sudden increase in pulmonary venous pressure
• pulmonary edema
• frequently cardiogenic shock

Clinical manifestations

• abrupt onset of dyspnea, pulmonary edema, cardiogenic shock
• clinical diagnosis of acute mitral regurgitation in patients with acute heart failure can be difficult
• holosystolic murmur at the apex radiating to the axilla
  • if severe, may be short or absent
• P2 & soft S3, right heart failure

Diagnostic procedures

• electrocardiogram reflects underlying pathology, i.e. acute MI
• echocardiogram
  • flail mitral leaflet with attached papillary muscle head
  • transesophageal echocardiogram (TEE) if transthoracic echocardiogram (TTE) inadequate (may be initial procedure)
  • diagnosis of acute mitral regurgitation in patients with acute heart failure can be difficult
• pulmonary artery catheter
  • large v waves in pressure tracing

Differential diagnosis

• ruptured papillar muscle due to ischemia
• infections endocarditis
• rupture chordae tendineae due to myxomatous valve

Management

• Medical management:
  • nitrate (nitroprusside)
    • afterload reduction
    • reduce mean arterial pressure to 60 mm Hg
    • venodilating effect may eliminate need for furosemide
  • furosemide (loop diuretic) with or without nitrates
    • preload reduction
    • reduce pulmonary congestion
  • hydralazine if hemodynamically stable
  • add nitroglycerin if symptomatic after vasodilators & loop diuretic
  • dobutamine, amrionone or milrinone if hypotensive
  • intra-aortic balloon counterpulsation if hemodynamically unstable
• Surgery:
  • indicated urgently in acute mitral regurgitation with hemodynamic instability despite medical management
  • surgery should be postponed if possible for several days in patients with infective endocarditis while antibiotic therapy is initiated
  • mitral valve repair with preservation of the native valve has become the procedure of choice
    • benefits of repair versus replacement
      • better preservation of left ventricular systolic function
      • improved intermediate term survival
      • lower incidence of chronic atrial fibrillation
      • lack of need for long-term anticoagulation for patients in sinus rhythm

More general terms

• mitral regurgitation (MR)

Additional terms

• heart murmur
• mitral valve