Mitral valve anatomy

Text Genevieve Carbonatto

The mitral valve apparatus consists of the

  •  left atrial wall
  • annulus
  • 2 leaflets
  • chordae tendinae
  • papaillarymuscles
  • left ventricular wall

The MV has 2 leaflets, the anterior and posterior leaflets

The anterior leaflet is

  • Larger and thicker than the posterior leaflet
  • Attached to the anterior mitral annulus which is in continuity with the non coronary and left coronary cusps of the aortic valve

The posterior leaflet is

  • Crescent shaped
  • Small than the anterior leaflet but has a greater circumferential attachment length to the posterior annulus
  • The atrial myocardium is in continuity with the atrial surface of the posterior leaflet

The annulus

  • is a pliable  fibrous ring changing shape during the cardiac cycle
  • it is a term to describe the  junctional zone which separates the  LA from the LV
  • it gives attachment to the mitral valve
  • it functions as a sphincter which contracts and reduces the surface area of the valve during systole
  • Contraction promotes valve competence
  • Dilatation (as in ischaemic or dilated cardiomyopathy) causes mitral regurgitation because of poor leaflet apposition

Chordae tendinae, papillary muscles and the left ventricle

There are 25 chordae which are attached the valves and the papillary muscles. They anchor the valves during systole to prevent prolapse of the valves.

Papillary and LV

  • The papillary muscles contract during systole
  • The anteromedial papillary muscle has a dual supply (supplied by the LAD and Lcx arteries)
  • The posteriomedial papillary muscle has a single blood supply (RCA)
  • Infarction can lead to valve incompetence or rupture of the PM papillary muscle

Summary

The mitral valve is a complex apparatus. Left atrial dilatation, annulus dysfunction, leaflet pathology, chordae or papillary muscle dysfunction and ventricular wall geometry and function will have an effect on mitral valve function

 

 

 

 

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