Simplified Anatomy of Mitral Valve

1. Mitral Valve
Anatomy

2. Mitral Valve Function
• Regulates blood flow in 2 ways:
• Forward towards left ventricle (LV)
in diastole
• Prevents backflow towards left
atrium (LA) in systole
• Helps regulate size, geometry and
function of the LV

3. Mitral
Valve Components
1. Mitral Annulus
2. Mitral Leaflets
3. Commissures
4. Chordae Tendinae
5. Papillary Muscles

4. 1. Mitral Annulus
Anatomical
structure that
separates the LV
& LA

5. 2. Mitral Leaflets
• Mitral Leaflets & Scallops: Thin and pliable leaflets
that contain scallops which represent segmental
markers.
• Leaflets thin & pliable
• Scallops serve as segmental markers of leaflets
• 2 Leaflets with 3 Scallops
Anterior Leaflet (AML): larger & thicker
• Dome-shaped
• Scallops: A1 (lateral), A2 (central), A3 (medial)
Posterior Leaflet (PML): thinner & more flexible
• Crescent shaped
• Scallops: P1 (lateral), P2 (central), P3 (medial)

6. 2. Mitral Leaflets

7. 3. Commissures
Commissures: 2 specific sites where the leaflets insert
and join into mitral annulus
Anterolateral Commissure
Posteromedial Commissure

8. 4. Chordae Tendinae
Chordae Tendinae: Fibrous strings that attach specific
portions of mitral leaflets to papillary muscle tips
Normal average length is around 20mm
Normal average thickness is 1-2mm
Key items to look for: thickening, fusion, calcification,
elongation, rupture

9. 4. Chordae Tendinae
Three classified types of chordae tendinae
based on location of insertion:
Primary (marginal)- attaches at leaflet tips
(‘coaptation line’)
Function to maintain coaptation of
leaflets
Failure of primary leads to rupture or
elongated chordae
Cause development of prolapse or flail
leaflet
Secondary (basal)- attaches at mid-body of
leaflets
Provides support length to leaflets
Thicker & longer
Can rupture & not damage coaptation
or develop regurgitation
Tertiary– attaches at base of leaflets
Function as structural support

10. 5. Papillary Muscles
Papillary Muscles: Large
trabeculae muscles that
branch from 1/3rd of LV,
connecting chordae to mitral
leaflets
2 papillary muscles:
Anterolateral (APM):
Dual blood supply (LAD &
Cx)
Posteromedial (PPM):
Single blood supply (Either
RCA or LCX)
Prone to injury from MI
due to single blood supply

11. Mitral Valve Zones
If we zoom in on the mitral
leaflets from the atrial
surface, we can identify two
zones.
Body (‘Smooth’) Zone:
surface area on leaflet body
Coaptation (‘Rough’) Zone:
represents the coaptation
area of leaflets
Crucial area to observe in
assessment of mitral
valve function

12. Mitral valve apparatus components in normal and
diseased states

13. Mitral valve prolapse:
The schematic shows bileaflet
mitral valve prolapse, with
superior displacement of the
papillary muscle tip, “tugged” by
the leaflets, and excessive leaflet
and chordal tissue and mobility.
Leaflet coaptation is displaced into
the left atrium superior to the
annular plane (dashed line).

14. Functional/ischemic mitral
regurgitation:
The papillary muscle (medial in
inferior myocardial infarction) is
displaced posteriorly, laterally and, to
the extent allowed by the chords,
apically (arrow) due to left ventricular
local dilatation & remodeling (arrows)
caused by MI (shaded area). The LV
wall-PM displacement tethers the
mitral leaflets apically and limits
coaptation. There is 20 often not
enough leaflet tissue to compensate
for leaflet tenting (area apical to the
dashed line), resulting in mitral
regurgitation (red lines).

15. Hypertrophic cardiomyopathy:
The geometry of the left ventricle and papillary
muscles is altered by myocardial hypertrophy
(interventricular septum, double arrow). The
papillary muscles are enlarged and displaced
anteriorly (arrow) and closer to each other (not
shown). This decreases intercommissural leaflet
tension and moves the coaptation point and
distal leaflets toward the left ventricular
outflow tract. Like a sail catching a breeze, the
distal anterior leaflet and/or posterior leaflet if
elongated, is at risk of being displaced into the
LV outflow tract by blood-flow drag. If anterior
leaflet displacement is severe enough and
posterior leaflet apposition restricted, mitral
regurgitation will occur (red lines).

16. Key Tips
• Evaluation of the Mitral Valve includes all
components that make up the Mitral Apparatus
• Visualization of scallops can vary per scanning
window and angulation of specific window
• Understanding the structure and function of all
components can aid in diagnosing pathology
• Anterior leaflet is more fixed than the posterior,
causing the posterior leaflet to be more prone to
remodeling, distortion of shape or damage

17. Key Tips
• Anterior leaflet is not anatomically divided into
scallops like the posterior leaflet is, but for
pathological guidance, the anterior scallops mimic
the posterior leaflets
• Scallops are labeled 1 to 3 based from lateral to
medial segments In regards to which papillary
muscle supplies chordae to which scallops…
- Anterolateral papillary muscle = lateral scallops (A1,
P1) & lateral half of A2, P2
- Posteromedial papillary muscle = medial scallops
(A3, P3) & medial half of A2, P2
• Chordae play a key role in the structure and
function of mitral leafets