Barlow Syndrome

Barlow Syndrome (Mitral Valve Prolapse)

Barlow Syndrome, also known as Mitral Valve Prolapse (MVP), is a common valvular heart condition characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. It was first described by John Brereton Barlow in 1963.

Epidemiology

Prevalence: 2-3% of the general population
More common in women (2:1 ratio)
Usually diagnosed in young adults, but can affect all age groups
Often familial, suggesting genetic predisposition

Anatomy Review

The mitral valve consists of two leaflets (anterior and posterior), the annulus, chordae tendineae, and papillary muscles. In MVP, one or both leaflets prolapse into the left atrium during systole, sometimes causing mitral regurgitation.

Pathophysiology of Barlow Syndrome

Structural Abnormalities

Myxomatous degeneration of the mitral valve leaflets
Elongation of the chordae tendineae
Annular dilatation
Excess leaflet tissue ("Barlow's valve")

Genetic Factors

Several genetic loci have been associated with MVP, including:

MMVP1 on chromosome 16p11.2-p12.1
MMVP2 on chromosome 11p15.4
MMVP3 on chromosome 13q31.3-q32.1

Histological Changes

Microscopic examination reveals:

Expansion of the spongiosa layer
Disruption of the fibrosa layer
Increased proteoglycan deposition
Altered collagen composition

Clinical Features of Barlow Syndrome

Symptoms

Many patients are asymptomatic. When present, symptoms may include:

Palpitations
Chest pain (typically non-anginal)
Dyspnea
Fatigue
Anxiety
Dizziness or lightheadedness

Physical Examination

Mid-systolic click: Due to sudden tensing of the mitral apparatus
Late systolic murmur: If mitral regurgitation is present
Dynamic auscultatory changes with maneuvers:
- Valsalva maneuver: Click moves closer to S1, murmur lengthens
- Squatting: Click moves away from S1, murmur shortens
- Standing: Click moves closer to S1, murmur lengthens

Associated Conditions

Marfan syndrome
Ehlers-Danlos syndrome
Osteogenesis imperfecta
Graves' disease

Diagnosis of Barlow Syndrome

Echocardiography

The gold standard for diagnosis. Criteria include:

Displacement of one or both mitral leaflets ≥2 mm above the mitral annulus plane in long-axis view
Maximal leaflet thickness ≥5 mm ("Barlow's valve")
Redundant chordae tendineae
Mitral annular dilatation

Electrocardiogram (ECG)

May show:

T-wave inversions in inferior leads
Frequent premature ventricular contractions
Rarely, prolonged QT interval

Cardiac MRI

Used for complex cases or when echocardiography is inconclusive. Provides detailed anatomical assessment and quantification of regurgitation.

Differential Diagnosis

Rheumatic mitral valve disease
Infective endocarditis
Coronary artery disease
Hypertrophic cardiomyopathy

Management of Barlow Syndrome

Asymptomatic Patients

Reassurance and education
Regular follow-up with echocardiography (frequency depends on severity)
Endocarditis prophylaxis no longer routinely recommended

Symptomatic Patients

Medical management:

Beta-blockers for palpitations or chest pain
Anticoagulation if atrial fibrillation develops
Diuretics for symptoms of volume overload

Surgical intervention (for severe mitral regurgitation):

Mitral valve repair (preferred option)
Mitral valve replacement (if repair not feasible)

Indications for Surgery

Symptomatic severe mitral regurgitation
Asymptomatic severe mitral regurgitation with:
- Left ventricular ejection fraction ≤60%
- Left ventricular end-systolic diameter ≥40 mm
- New onset atrial fibrillation
- Pulmonary hypertension

Prognosis

Generally good for most patients. Factors associated with worse outcomes include:

Severe mitral regurgitation
Reduced left ventricular function
Pulmonary hypertension
Advancing age