Mitral annular dilation

Mitral annular dilation refers to an increased mitral annulus in relation to the size of the mitral valvular leaflets and is a potential cause for mitral regurgitation.

Epidemiology

Associations

Mitral annular dilation is seen in the following clinical conditions ^1-3:

• secondary mitral regurgitation
  • atrial functional mitral regurgitation
• left atrial dilation
  • heart failure with a preserved ejection fraction
  • atrial fibrillation
• left ventricular dilation
  • dilated cardiomyopathy
  • ischemic cardiomyopathy

Pathology

Mitral annular dilation can be found as a contributing factor of mitral regurgitation and can be found in the Carpentier types I or IIIb depending on whether it is associated with left atrial or left ventricular dilation ³. If isolated it is usually associated with compensatory leaflet growth, 

Etiology

Causes of mitral annular dilation include the following ^1,2: 

• ischemic heart disease
• atrial fibrillation
• dilated cardiomyopathy

Radiographic features

Echocardiography

The following cut-off values are considered criteria for annular dilation ^1,2: 

• systolic anteroposterior diameter >35 mm (parasternal long axis) 
• ratio of the systolic annular diameter/diastolic anterior leaflet length >1.3

MRI

The following end-systolic annular measurements are considered abnormal according to a study (according to image plane) ⁴: 

• 2-chamber view: >2.5 cm/m² (male), >2.5 cm/m² (female)
• 3-chamber view: >2.2 cm/m² (male), >2.3 cm/m² (female)
• 4-chamber view: >2.3 cm/m² (male), >2.4 cm/m² (female)

Radiology report

The radiological report should include a description of the following features:

• mitral annulus diameter
• mitral regurgitation and severity
• cardiac volumes (left ventricular and left atrial) and cardiac function