Mitral Valve Anatomy:
Last week we wrapped up our right heart blog series. Be sure to keep an eye out for our Right Heart E-Book that will be available soon!
This week, we are kicking off our mitral regurgitation (MR) blog series! The ASE, recently released updated guidelines, for the proper methods to quantify MR. We at CardioServ, want to help break it down, into a more enjoyable learning process. Our goal is to help you, incorporate these methods into daily scanning practices! We look forward to feedback and comments, as we are all here to learn and grow together!
In order to identify pathology of a valve, we must be familiar with the basic anatomy first! Can you name five components of the mitral valve apparatus? Read on, and master mitral valve anatomy!
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
FIVE MITRAL VALVE COMPONENTS
1. Mitral Annulus
2. Mitral Leaflets
3. Commissures
4. Chordae Tendinae
5. Papillary Muscles
1. MITRAL ANNULUS
Mitral Annulus: Anatomical structure that separates the LV & LA
2. MITRAL LEAFLETS
Mitral Leaflets & Scallops: Thin and pliable leaflets that contain scallops which represent segmental markers.
2 Leaflets with 3 ScallopsAnterior Leaflet (AML): larger & thickerDome-shaped
Scallops: A1 (lateral), A2 (central), A3 (medial)
Posterior Leaflet (PML): thinner & more flexibleCrescent shaped
Scallops: P1 (lateral), P2 (central), P3 (medial)
Leaflets thin & pliable
Scallops serve as segmental markers of leaflets
3. COMMISSURES
Commissures: 2 specific sites where the leaflets insert and join into mitral annulus
Anterolateral Commissure
Posteromedial Commissure
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
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 leafletsProvides support length to leaflets
Thicker & longer
Can rupture & not damage coaptation or develop regurgitation
Tertiary– attaches at base of leafletsFunction as structural support
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
MITRAL VALVE ZONES
The mitral apparatus has very specific details that make up the large picture of the ‘mitral valve’. If we zoom in on the mitral leaflets from the atrial surface, we can identify two zones that are used for describing location of pathology seen.
Body (‘Smooth’) Zone: surface area on leaflet body
Coaptation (‘Rough’) Zone: represents the coaptation area of leafletsCrucial area to observe in assessment of mitral valve function
KEY TIPS TO TAKE AWAY
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
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
CONCLUSION
This week, we reviewed mitral valve anatomy, to lay the foundation for our in-depth review of quantification of mitral valve regurgitation. You can now confidently identify 5 components of the mitral valve apparatus! Join us next week, as we start our discussion on correct scanning techniques for the mitral valve! We look forward to hearing feedback and comments from our readers!
Andrea Fields MHA, RDCS
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References:
Prokšelj, K. (2015). Echocardiography Of The Mitral Valve. International Symposium MITRAL VALVE DISEASES IN CHILDREN AND ADULTS. doi:10.5644/pi2017.168.03
Zoghbi, W. A., MD, Adams, D., RCS, RDCS, FASE, & Bonow, R. O., MD. (2017). Recommendations for Noninvasive Evaluation of Native Valvular Regurgitation. JASE,30(4), 318-334. Retrieved June 6, 2017.
Zamorano, J. L., MD, & Badano, L. P. (2011). EAE/ASE Recommendations for the Use of Echocardiography in New Transcather Interventions for Valvular Heart Disease. JASE,24(9), 957-960. Retrieved June 6, 2017.