Myxomatous mitral valve degeneration, myxomatous degeneration of the mitral valve, myxomatous mitral valve disease or simply myxomatous mitral valve is a non-inflammatory progressive alteration of the mitral valve structure associated with mitral valve prolapse and mitral insufficiency.
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Terminology
Myxomatous mitral valve degeneration is also termed ‘Barlow disease’ yet the name actually refers to the clinical syndrome describing a late systolic murmur and a non-ejection systolic click associated with mitral valve prolapse 1.2.
Epidemiology
Myxomatous degeneration of the mitral valve is a common form of valvular heart disease with an estimated frequency of 0.6-2.4% 1 and seems to be more common in females, but symptoms seem to be more severe in men 2.
Associations
Myxomatous degeneration of the mitral valve is closely associated with the following conditions 1-6:
- mitral valve prolapse (>85%)
- flail leaflet
- mitral annular disjunction
- mitral annular dilation
- Marfan syndrome
- Ehlers-Danlos syndrome
- Loeys-Dietz syndrome
Clinical presentation
Patients can present with a systolic click and a mid to late systolic murmur on auscultation indicating mitral valve prolapse 1,2.
Complications
Complications of myxomatous degeneration of the mitral valve include the following conditions 1-6:
- mitral valve prolapse
- infective endocarditis
- mitral insufficiency
- chordae tendineae lengthening or rupture
- sudden cardiac death
Pathology
Myxomatous degeneration of the mitral valve is a histopathological diagnosis and characterized by myxomatous altered thickened mitral leaflets and involvement of the chordae tendineae leading to a loss of mechanical leaflet integrity 3. The posterior mitral leaflet is more frequently affected 2.
Macroscopic appearance
On gross appearance, myxomatous degeneration is characterized by ample leaflet thickening not only involving the valve but also the chordae tendineae 1.
Microscopic appearance
Microscopically myxomatous mitral valve degeneration shows the following features 1-3:
- thickening and proliferation of the spongiosa
- accumulation and pooling of glycosaminoglycan
- disruption of the fibrosa by the myxomatous extracellular matrix with cystic appearance
- collagen fragmentation of the fibrous layer
Genetics
Some cases have been linked to a familial inheritance mapped to the Xq28 location 3,7.
Radiographic features
The main imaging feature of myxomatous mitral valve degeneration is a thickening of one or both mitral leaflets 3.
Echocardiography
Echocardiography is considered is usually the first-line imaging modality for the evaluation of mitral valvular disorders. It can identify mitral valve thickening, assess leaflet coaptation, depict flail leaflets and other associated conditions as mitral prolapse and mitral insufficiency as well as mitral annular dilation 5.
CT
Due to good spatial resolution, cardiac CT can assess the thickness of the mitral leaflets and can detect leaflet flail. It can also identify calcification of the chordae tendineae.
MRI
Cardiac MRI can detect valvular thickening and associated findings as mitral prolapse, mitral insufficiency and mitral annular disjunction as well as complications e.g. chordae tendineae rupture 5.
Radiology report
The radiological report should include a description of the following features:
- mitral valve thickening and location
- associated findings
- left ventricular volumes and measurements
Treatment and prognosis
Management is subject to complications but in the setting of mitral valve regurgitation, it is the most common indication for mitral valve repair or replacement 1,3. In asymptomatic individuals, without mitral regurgitation, the management will consist in watchful waiting 1.
History and etymology
The clinical presentation and significance of systolic click and late systolic murmur on auscultation have been first demonstrated by JB Barlow and WA Pocock in 1963 8.
Differential diagnosis
Conditions mimicking the imaging appearance of myxomatous mitral valve degeneration include: