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

1. Regulates blood flow in 2 ways:
   • Forward towards left ventricle (LV) in diastole
   • Prevents backflow towards left atrium (LA) in systole
2. 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 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)
• 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 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

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.

1. Body (‘Smooth’) Zone: surface area on leaflet body
2. Coaptation (‘Rough’) Zone: represents the coaptation area of leaflets
   • Crucial area to observe in assessment of mitral valve function

 Key Tips to Take Away

1. Evaluation of the Mitral Valve includes all components that make up the Mitral Apparatus
2. Visualization of scallops can vary per scanning window and angulation of specific window
3. Understanding the structure and function of all components can aid in diagnosing pathology
4. Anterior leaflet is more fixed than the posterior, causing the posterior leaflet to be more prone to remodeling, distortion of shape or damage
5. Anterior leaflet is not anatomically divided into scallops like the posterior leaflet is, but for pathological guidance, the anterior scallops mimic the posterior leaflets
6. Scallops are labeled 1 to 3 based from lateral to medial segments
7. 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
8. 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

Stay Connected: LinkedIn, Facebook, Twitter, Instagram

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.