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Mitral Regurgitation

Mitral Regurgitation is a topic covered in the Washington Manual of Medical Therapeutics.

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General Principles

  • Prevention of MR is dependent on the integrated and proper function of the MV (annulus and leaflets), subvalvular apparatus (chordae tendineae and papillary muscles), and LA and LV; abnormal function or size of any one of these components can lead to MR.
  • Primary MR, or organic MR, refers to MR caused primarily by lesions to the valve leaflets and/or chordae tendineae (i.e., myxomatous degeneration, endocarditis, rheumatic).
  • Secondary MR, or functional MR, refers to MR caused primarily by ventricular dysfunction usually with accompanying annular dilatation (i.e., dilated cardiomyopathy and ischemic MR).
  • It is critical to define the mechanism of MR and the time course (acute vs. chronic) because these significantly impact clinical management.

Etiology

  • Primary MR
    • Degenerative (overlap with MV prolapse syndrome)
      • Usually occurs as a primary condition (Barlow disease or fibroelastic deficiency) but has also been associated with heritable diseases affecting the connective tissue including Marfan syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, etc.
      • May be familial or nonfamilial. Occurs in 1.0–2.5% of the population (based on stricter echocardiography criteria) in a female-to-male ratio of 2:1.
      • Most common reason for MV surgery.
      • Myxomatous proliferation and cartilage formation can occur in the leaflets, chordae tendineae, and/or annulus.
    • Rheumatic
      • May be pure MR or combined MR/MS.
      • Caused by thickening and/or calcification of the leaflets and chords.
    • Infective endocarditis: Usually caused by destruction of the leaflet tissue (i.e., perforation).
  • Secondary MR
    • Dilated cardiomyopathy
      • Mechanism of MR is due to both of the following:
      • Annular dilatation from ventricular enlargement.
      • Papillary muscle displacement due to ventricular enlargement and remodeling prevents adequate leaflet coaptation.
    • Ischemic
      • Ischemic MR is mostly a misnomer, because this is primarily postinfarction MR, not MR caused by active ischemia.
      • Mechanism of MR usually involves one or both of the following:
        • Annular dilatation from ventricular enlargement.
        • Local LV remodeling with papillary muscle displacement (both the dilatation of the ventricle and the akinesis/dyskinesis of the wall to which the papillary muscle is attached can prevent adequate leaflet coaptation).
      • Rarely, MR may develop acutely from papillary muscle rupture (more commonly of the posteromedial papillary muscle).
  • Other causes

    Congenital, infiltrative diseases (i.e., amyloid), SLE (Libman-Sacks lesion), hypertrophic cardiomyopathy with obstruction, mitral annular calcification, paravalvular prosthetic leak, drug toxicity (e.g., Fen-phen)

  • Acute causes
    • Ruptured papillary muscle, ruptured chordae tendineae, infective endocarditis

Pathophysiology

Figure 6-2. Acute mitral regurgitation.

CO, cardiac output; EF, ejection fraction; HR, heart rate; LA, left atrium; LAP, left atrial pressure; LV, left ventricle; LVEDP, left ventricular end-diastolic pressure; SV, stroke volume.

Figure 6-3. Chronic mitral regurgitation.

CO, cardiac output; EF, ejection fraction; LA, left atrium; LAP, left atrial pressure; LV, left ventricle; LVEDP, left ventricular end-diastolic pressure; MR, mitral regurgitation; PH, pulmonary hypertension; SV, stroke volume.

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Citation

Williams, Dominique, et al., editors. "Mitral Regurgitation." Washington Manual of Medical Therapeutics, 35th ed., Wolters Kluwer Health, 2016. Washington Manual, www.unboundmedicine.com/washingtonmanual/view/Washington-Manual-of-Medical-Therapeutics/602124/all/Mitral_Regurgitation.
Mitral Regurgitation. In: Williams D, Ramgopal R, Gdowski M, et al, eds. Washington Manual of Medical Therapeutics. 35th ed. Wolters Kluwer Health; 2016. https://www.unboundmedicine.com/washingtonmanual/view/Washington-Manual-of-Medical-Therapeutics/602124/all/Mitral_Regurgitation. Accessed May 21, 2019.
Mitral Regurgitation. (2016). In Williams, D., Ramgopal, R., Gdowski, M., Dretler, A., & Bhat, P. (Eds.), Washington Manual of Medical Therapeutics. Available from https://www.unboundmedicine.com/washingtonmanual/view/Washington-Manual-of-Medical-Therapeutics/602124/all/Mitral_Regurgitation
Mitral Regurgitation [Internet]. In: Williams D, Ramgopal R, Gdowski M, Dretler A, Bhat P, editors. Washington Manual of Medical Therapeutics. Wolters Kluwer Health; 2016. [cited 2019 May 21]. Available from: https://www.unboundmedicine.com/washingtonmanual/view/Washington-Manual-of-Medical-Therapeutics/602124/all/Mitral_Regurgitation.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Mitral Regurgitation ID - 602124 ED - Williams,Dominique, ED - Ramgopal,Rajeev, ED - Gdowski,Mark, ED - Dretler,Alexandra, ED - Bhat,Pavat, BT - Washington Manual of Medical Therapeutics UR - https://www.unboundmedicine.com/washingtonmanual/view/Washington-Manual-of-Medical-Therapeutics/602124/all/Mitral_Regurgitation PB - Wolters Kluwer Health ET - 35 DB - Washington Manual DP - Unbound Medicine ER -