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