Anatomy of the Mitral Valve

Mitral Valve OutlineAnatomy of the Mitral ValveStandard Views of the Mitral Valve - Part 1Standard Views of the Mitral Valve - Part 2Standard Views of the Mitral Valve - Part 3Standard Views of the Mitral Valve - Part 43D Views of the Mitral ValveEtiology of Mitral Stenosis2D Echocardiography of Mitral StenosisDoppler Assessment of Mitral Stenosis - Part 1Doppler Assessment of Mitral Stenosis - Part 2Etiology and Classification of Mitral Regurgitation2D Echocardiography of Mitral Regurgitation - Part 12D Echocardiography of Mitral Regurgitation - Part 22D Echocardiography of Mitral Regurgitation - Part 32D Echocardiography of Mitral Regurgitation - Part 43D Evaluation of Mitral RegurgitationDoppler Evaluation of Mitral RegurgitationColor Flow Doppler of Mitral Regurgitation - Part 1Color Flow Doppler of Mitral Regurgitation - Part 2Color Flow Doppler of Mitral Regurgitation - Part 3Color Flow Doppler of Mitral Regurgitation - Part 4Color Flow Doppler of Mitral Regurgitation - Part 5Color Flow Doppler of Mitral Regurgitation - Part 6Color Flow Doppler of Mitral Regurgitation - Part 7SummaryCME and Self Assessment Exams
Introduction

The mitral valve complex consists of six components:

  • Left Atrial Wall
  • Mitral Valve Annulus
  • Mitral Valve Leaflets
  • Chordae Tendinae
  • Papillary Muscles
  • Left Ventricular Myocardium

Derangement of one or multiple components of the mitral valve complex can cause mitral valve dysfunction.  The annulus of the mitral valve serves as an attachment site or fulcrum for the valve leaflets and exhibits a reduction in annular dimensions from diastole to systole.  The mitral valve leaflets differ in shape as well as attachment to the mitral valve annulus: the anterior mitral valve leaflet is semi-circular in shape and attaches to approximately one-third of the annulus while the posterior mitral leaflet is somewhat rectangular in shape and attaches to the remaining two-thirds of the mitral annulus. 

script
Mitral Valve Complex Components
 
script
   
MItral Valve (ME 4CV) Video Mitral Valve Leaflets, Chordae and Papillary Muscles
Mitral Valve Leaflets/Scallops
 

The base to free-edge length of the anterior leaflet is approximately two-times that of the posterior mitral valve leaflet.  The anterior leaflet is in continuity with the cardiac fibrous skeleton while the posterior mitral leaflet is primarily a continuation of the mural endocardium of the atrium.  Therefore, the posterior annulus is much thinner and lacks the surrounding support structures of the anterior leaflet.  The overall surface area of the leaflets is nearly equivalent.  Both of the leaflets are covered by endocardium which is reflected from the walls of the left atrium and left ventricle.  The leaflets are limited in mobility by their basal attachments to the annulus as well as by the chordal tendon attachments to the free edge of the leaflets. 

Each leaflet can be divided into scallops.  Scallops are anatomically identifiable sections of the leaflet.  Each scallop will receive chordae tendinae from one or both of the papillary muscles.  The scallops appear as small outpouchings of each leaflet and are numbered or named by the leaflet from which they originate. The scallops are sometimes referred to as segments or cusps of the mitral valve also.

Mitral Valve Leaflets
Courtesy of the Cleveland Clinic
Standard Nomenclature of the Mitral Valve
 
Carpentier/ASE Nomenclature

Carpentier's original description of the mitral valve leaflets has been adopted by the American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists (SCA) when referring to the mitral valve. The standardized nomenclature identifies three scallops of the posterior mitral valve leaflet labeled as: P1, the lateral scallop; P2, the middle scallop; and P3, the medial scallop. Indentations or clefts along the free margin of the posterior mitral valve leaflet allow identification of these scallops. The P1 scallop is adjacent to the anterolateral commissures and P3 is adjacent to the posteromedial commisures. The anterior mitral valve leaflet is divided for description into 3 segments: A1, A2 and A3, located opposite the corresponding segments of the posterior mitral valve leaflet.
Surgeon's View TEE View TTE View
Mitral Valve Cusps Courtesy of the Cleveland Clinic
Duran Nomenclature
 
Duran's nomenclature for the mitral valve follows a classical description of the anatomical arrangement of the mitral valve.  Duran's nomenclature identifies three cusps of the anterior and posterior mitral valve leaflets.  The anterior leaflet contains a central anterior cusp which is split into segments, A1 (lateral) and A2 (medial),  and surrounded by two segmental cusps, C1 (lateral) and C2 (medial).  The posterior leaflet also identifies three cusps.  The posterior central cusp is split into two segments, PM 1 (lateral) and PM2 (medial), and surrounded by two segmental cusps, P1 (lateral) and P2 (medial).  When discussing mitral valvular anatomy with other medical consultants, it is imperative that the communication occurs using the same nomenclature.
Surgeon's View TEE View TTE View
Durran Nomenclature Courtesy of the Cleveland Clinic
Papillary Muscles and Chordae Tendinae
 
The chordal tendons arise and subdivide from both papillary muscles and connect to both of the mitral valve leaflets. The anterolateral papillary muscle attaches to the A1/P1 and A2/P2 scallops of the mitral valve.  The posteromedial papillary muscle attaches to the A2/P2 and A3/P3 scallops of the mitral valve.  Subdivisions of chordal tendons can be classified as primary, secondary and tertiary chordae.  The primary chordae attaches to the leaflet edges, secondary chordae attaches to the body of each leaflet, and tertiary chordae attach to the base of the mitral valve leaflets.  Approximately 120 third-order(tertiary) chordal tendons attach to the ventricular undersurface of the mitral valve leaflets.  The primary and secondary chordae tendinae originate from the papillary muscles.  Tertiary chordae tendinae originate from the myocardial wall.  Chordal tendons consist of fibrous tissue with an endothelial lining and do not stretch more than 10% under physiologic conditions due to their collagenous make up. 
 
Papillary Muscle and Cusp Attachment Chordae Tendinae Attachments
 
Typically the anterolateral papillary muscle is a single muscle and larger than posteromedial papillary muscle.   The posteromedial papillary muscle may have several heads.  Proper motion of the mitral valve is dependent on each of the components of the mitral valve complex including coordinated participation of the papillary muscles and surrounding ventricular myocardium.  The anterolateral papillary muscle has a dual blood supply - the left anterior descending artery and the circumflex artery.  The posteromedial papillary muscle has a single blood supply - right coronary artery. Therefore, the posteromedial papillary muscle is more prone to ischemia.
Labels     1X 2X 3X 4X
No Labels 1X 2X 3X 4X
Papillary Muscle Image