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.
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Epidemiology
Associations
Mitral annular dilation is seen in the following clinical conditions 1-3:
- secondary mitral regurgitation
- atrial functional mitral regurgitation
- left atrial dilation
- 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:
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