What is the normal measurement of the mitral annulus in adults?

Normal Mitral Annular Measurements in Adults

The normal mitral valve annulus diameter in adults is 28 ± 5 mm when measured in the four-chamber view. 1

Gender-Specific Measurements

Mitral Annular Diameters

• End-systolic measurements:

  • Males: 3.44 cm in parasternal long axis view 2
  • Females: 3.11 cm in parasternal long axis view 2
  • Males: 3.3 ± 0.4 cm (1.7 ± 0.2 cm/m² indexed) in 3-chamber view 3
  • Females: 3.0 ± 0.4 cm (1.8 ± 0.2 cm/m² indexed) in 3-chamber view 3

• End-diastolic measurements:

  • Males: 3.15 cm in parasternal long axis view 2
  • Females: 2.83 cm in parasternal long axis view 2
  • Males: 2.9 ± 0.4 cm (1.5 ± 0.2 cm/m² indexed) in 3-chamber view 3
  • Females: 2.6 ± 0.4 cm (1.6 ± 0.2 cm/m² indexed) in 3-chamber view 3

Intercommissural vs. Anteroposterior Dimensions

• The mitral annulus has an elliptical shape with two axes 4:
  • Intercommissural (major axis): 27-46 mm (16-23 mm/m²) at end-systole 4
  • Anteroposterior (minor axis): 22-36 mm (13-18 mm/m²) at end-systole 4

Dynamic Changes During Cardiac Cycle

The mitral annulus is not static but undergoes significant changes throughout the cardiac cycle:

• Mitral annular area (MAA) fractional shortening: 35 ± 10% 5
• Anteroposterior diameter change: 25 ± 10% 5
• Mitral annular circumference change: 35 ± 10% 5
• Anterolateral-posteromedial diameter change: 13 ± 8% 5

Key Dynamics

• The mitral annulus begins to contract before mitral valve closure, during left atrial contraction 5
• Minimum mitral annular area occurs at mitral valve closure 5
• Maximum mitral annular area occurs at end-systole 5
• Maximum anteroposterior diameter occurs during early diastolic filling 5

Clinical Implications

• Significant mitral annular dilatation is defined as a diastolic diameter of >21 mm/m² (>35 mm) 1
• Normal contraction (decrease in annular area during systole) of the mitral annulus is approximately 25% 1
• Abnormal mitral annular dynamics, particularly mitral annulus disjunction, can be associated with mitral valve prolapse and arrhythmias 6
• Proper assessment of mitral annular dimensions is crucial for:
  • Determining mechanisms of mitral regurgitation 2
  • Planning surgical or transcatheter interventions 3
  • Evaluating the need for annuloplasty during valve repair 1

Measurement Considerations

• Measurements should be indexed to body surface area for more accurate assessment 3, 4
• End-systolic measurements provide the most reproducible results 4
• Multiplane transesophageal echocardiography offers superior visualization for detailed measurements 4
• 3D echocardiography allows simultaneous visualization of the entire annulus throughout the cardiac cycle 5

When evaluating the mitral annulus, it's important to consider not only the absolute dimensions but also the dynamic changes throughout the cardiac cycle, as these can provide valuable insights into valvular and ventricular function.