MORPHOLOGY OF THE MITRAL VALVE

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MORPHOLOGY OF THE MITRAL VALVE

• M. Kuduvalli

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ELEMENTS OF MITRAL VALVE APPARATUS

• Annulus
• Leaflets
• Subvalvar apparatus
• - Chordae tendinae
• - Papillary muscles

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MITRAL ANNULUS

• Zone of junction which serves as attachment to
  the muscular fibres of the atrium, ventricle, and
  attachment of the mitral valve
• Attached to two fibrous trigones
• -The right fibrous trigone which forms a
  dense junction between the mitral,
  tricuspid and aortic (non-coronary
  cusp) annuli, and the membranous septum
• -The left fibrous trigone which lies
  between the aortic (left cusp) and the
  mitral annuli
• Between the two trigones, the mitral valve is in
  continuity with the aortic wall and there is no
  fibrous mitral annulus in this region

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FIBROUS SKELETON OF THE HEART
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SPATIAL RELATIONSHIP BETWEEN MITRAL, AORTIC AND
TRICUSPID VALVES
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MITRAL ANNULUS

• Mitral annulus is a dynamic structure
• Has a sphincter like function, effectively
  decreasing the valve area by about a quarter
  during systole
• This is secondary to contraction and relaxation
  of the basoconstrictor muscles (bulbospiral and
  sinospiral)
• Dilatation of the annulus occurs posteriorly

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IMPORTANT STRUCTURES SURROUNDING THE MITRAL
ANNULUS
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MITRAL LEAFLETS

• Form a continuous veil attached to the
  circumference of the mitral annulus
• Free edge hangs into the LV, and is split by
  indentations
• Two well defined and constant indentations
• - Anterolateral commissure
• - Posteromedial commissure

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MITAL LEAFLETS

• Commissural areas (identified by presence of
  commissural chordae) divide the continuous mitral
  veil into two leaflets
• - Anterior (aortic) leaflet
• - Posterior (mural) leaflet

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MITRAL LEAFLETS

• Covered with endocardium
• Distinct ridge on atrial side which
• - defines line of leaflet closure
• - separates leaflets into two zones
• - rough zone distal to the ridge
• (represents surface of coaptation)
• - clear zone proximal to the ridge

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ANTERIOR MITRAL LEAFLET

• Semicircular or triangular
• Attached to around 3/8th of circumference of the
  mitral annulus
• Has common attachment to the cardiac skeleton
  with
• - left coronary cusp
• of aortic valve
• - half of non-coronary cusp

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ANTERIOR MITRAL LEAFLET

• Rough zone receives the chordae tendinae
• Forms boundary dividing the outflow and inflow
  tracts of the left ventricle.

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ANTERIOR MITRAL LEAFLET

• Direct continuity between AML and the aortic wall
• Gap between aortic and mitral valves is filled
  with an inter-valvular septum. Fibrous mitral
  annulus is absent here

1.Intervalvular septum 2. AML 3. PML
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POSTERIOR MITRAL LEAFLET

• Quadrangular in shape
• Attached to around 5/8th of the circumference of
  the mitral annulus
• Margin has two indentations, forming three
  scallops
• - Anterolateral
• - Middle
• - Posteromedial
• Cleft chordae insert into these indentations

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MITRAL LEAFLETS
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POSTERIOR MITRAL LEAFLET

• Additional third zone, k/a basal zone, which is
  between the clear zone and the annulus. It
  receives insertion of the basal chordae
• Basal zone is most obvious in the middle scallop
  since the majority of basal chordae insert here

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SUBVALVAR APPARATUSPAPILLARY MUSCLES

• Two groups of LV papillary muscles
• - Anterolateral
• - Posteromedial
• Each group supplies chordae to their respective
  halves of both leaflets
• Arise from the anterior and posterior walls of
  the left ventricle respectively

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SUBVALVAR APPARATUSPAPILLARY MUSCLES

• May have one or more bellies each. Anterolateral
  usually has one
• Tip points towards the respective commissure

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SUBVALVAR APPARATUSPAPILLARY MUSCLES
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SUBVALVAR APPARATUSCHORDAE TENDINAE

• Fibrous strings that originate from tiny nipples
  on the apical portion of the two papillary
  muscles
• Majority have branching pattern, either soon
  after their origin from the papillary muscles, or
  just before their insertion into the leaflets

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SUBVALVAR APPARATUSCHORDAE TENDINAE
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COMMISSURAL CHORDAE

• Two in number, one for each commissure, with
  similar names
• Arise as a main stem which branches radially to
  insert into the free margins of the commissural
  regions
• Their attachment defines the extent of the
  commissural areas

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CHORDAE OF THE A.M.L

• Typically splits into 3 cords soon after its
  origin from the papillary muscles

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MAIN CHORDAE OF THE A.M.L.

• Two in number, one from each papillary muscle
• Inserted at 4-5 Oclock posteromedially and 7-8
  Oclock anterolaterally

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OTHER CHORDAE OF THE A.M.L.

• Paramedial chordae
• - Insert near the middle of the free edge
• Paracommissural chordae
• - Insert between the main chordae and the
  commissural chordae

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CHORDAE OF THE A.M.L.
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CHORDAE OF THE P.M.L.

• Basal chordae
• - Unique to the PML
• - Arise directly as single strands from the
  left ventricular free wall or from the small
  trabeculum carnae
• Rough zone chordae tendinae
• - Similar to AML chordae, but shorter and
  thinner
• Cleft chordae
• - Insert into indentations on the PML

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CHORDAE OF THE P.M.L.
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BLOOD SUPPLY OF THE MITRAL VALVE

• Mitral leaflets and chordae are avascular
• Papillary muscle supply
• - Anterolateral supplied by LAD and in
  addition, by the Diagonal or an OM from the
  Circumflex
• - Posterolateral variably supplied by
  branches of either the Lt. Circumflex or the
  RCA

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TYPES OF MITRAL VALVE PATHOLOGY

• Type I Normal leaflet motion
• - Annular dilatation
• - Leaflet perforation
• Type II Leaflet prolapse
• - Chordal rupture
• - Chordal elongation
• - Papillary muscle rupture
• - Papillary muscle elongation
• Type III Restricted leaflet motion
• - Restricted opening Commissural fusion,
  leaflet and chordal thickening
• - Restricted closure Excess tension on chordae
  during systole

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TYPES OF MITRAL VALVE PATHOLOGY
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REFERENCE POINT
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RHEUMATIC MITRALVALVE MORPHOLOGY

• Can manifest as
• - Stenosis
• - Regurgitation
• - Mixed
• Three primary pathological processes
• - Leaflet thickening
• - Chordal thickening, shortening and
  fusion
• - Coaptation of the edges of the leaflets,
  especially near the commissures

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RHEUMATIC MITRALVALVE MORPHOLOGY

• Leaflet thickening can progress to
• - Calcification, first of leaflet, and then
  peri-annular
• - Retraction, leading to combined stenosis
  and regurgitation
• Subvalvar apparatus involvment may lead to
  different degrees of subvalvar fusion

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ISCHEMIC MITRAL VALVE DISEASE

• Due to a combination of left ventricular wall
  akinesia or dyskinesia and ischemia of the
  papillary muscle itself, affecting the integrity
  of the subvalvar apparatus
• Papillary muscle necrosis can lead to rupture
  either at its attachment at the base to the LV
  wall or at its tip near the chordal attachments
• Leaflets and chordae are avascular structures,
  and are not directly involved in ischemic MR

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MYXOMATOUS DEGENERATION MORPHOLOGY

• Chordal elongation and rupture
• Thickening of mitral leaflets
• Redundancy of mitral leaflets, billowing into the
  left atrium in systole
• Degeneration and abnormal collagen synthesis in
  the region close to the chordal attachments

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INFECTIVE ENDOCARDITIS OF MITRAL VALVE

• Leaflet involvement, with vegetation formation
  and subsequent destruction of the leaflet
• Thickening and healing around chronic leaflet
  perforations
• Annular and periannular abscesses, subsequently
  involving the aortic valve
• Chordal detachment due to destruction of leaflet
  edges
• Rupture of chordae and papillary muscles due to
  their primary involvement

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OTHER DISEASES INVOLVING MITRAL VALVE

• Marfans and Ehler-Danlos syndromes
• - Annular dilatation
• - Chordal elongation
• Idiopathic calcification of the mitral annulus
• - particularly in the posterior area, with
  calcification extending into the LA
• - seen more frequently in elderly women

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OTHER DISEASES INVOLVING MITRAL VALVE

• HOCM associated with MR
• - Distortion of the AML from contact with
  the hypertrophic IVS during systolic
  anterior motion of the AML
• - Dilatation of the LV and the annulus in
  long standing HOCM

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