Anatomy of the Mitral Valve

  
 Objectives
 
  • Discuss the anatomy of the mitral valve complex
  • Discuss the deformation of the mitral valve annulus during the cardiac cycle
  • Discuss the orientation of the mitral valve leaflets to the aortic valve, coronary sinus and circumflex artery
  • Discuss the the standard nomenclature of the mitral valve
  • Discuss the different orientation of the mitral valve by TEE, TTE, and the Surgeon's View
  • Discuss the standard views of the mitral valve
  • Discuss the 2D, and Doppler signs of Mitral Stenosis
  • Discuss the severity of mitral stenosis and it's relationship to mitral valve area.
  • Discuss the mitral valve gradient and it's relationship to mitral valve area
  • Discuss the pressure half-time and it's relationship to mitral valve area
  • Discuss the 2D signs of mitral regurgitation
  • Discuss the classification of mitral regurgitation mechanism
  • Discuss pulmonary vein flow patterns and mitral regurgitation severity
  • Discuss CFD and mitral regurgitation severity
 
 
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. 

 




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