What is Barlow Disease?
Barlow disease is a severe form of degenerative mitral valve disease characterized by diffuse myxomatous degeneration with excessive leaflet tissue, multi-segment prolapse (often bileaflet), and marked annular dilatation 1.
Key Pathological Features
Barlow disease represents one end of the spectrum of degenerative mitral valve disease, distinct from fibroelastic deficiency 2, 3. The pathological hallmarks include:
- Diffuse myxomatous tissue affecting multiple leaflet segments
- Excess leaflet tissue with redundancy
- Bileaflet prolapse (both anterior and posterior leaflets commonly involved)
- Severe annular dilatation
- Completely dispersed collagen fiber orientation (in contrast to the highly aligned fibers in healthy valves) 4
- Multiple torn chordae across different scallops 1
The collagen microstructure in Barlow disease shows complete dispersion with two preferred orientations that vary across leaflet thickness, fundamentally altering the mechanical properties of the valve 4.
Relationship to Age-Related Valve Degeneration
No, Barlow disease does NOT occur as part of age-related valve degeneration—it is a distinct pathological entity separate from age-related degenerative changes 2, 3.
Critical Distinction
The guidelines and research clearly differentiate between two phenotypes of degenerative mitral valve disease 1:
- Fibroelastic deficiency - This is the age-related degenerative form, typically occurring in older patients with focal leaflet pathology and chordal rupture
- Barlow disease - A distinct myxomatous disease process with diffuse involvement, not simply an age-related phenomenon
The ACC/AHA guidelines specifically note a "forme fruste" category that represents an intermediate pathoanatomic form between fibroelastic deficiency and Barlow's disease 1, further emphasizing these are distinct disease processes rather than a continuum of age-related degeneration.
Clinical Implications
Surgical Complexity
Patients with Barlow disease require referral to experienced mitral valve surgeons at high-volume institutions due to the complexity of repair 1. The guidelines explicitly state that "patients with severe anterior, bileaflet, Barlow's, or mixed disease that may require extensive and complex reparative techniques should be preferentially referred to an experienced MV surgeon" 1.
Repair Approaches
Multiple surgical techniques may be required 5, 6:
- Non-resectional cordal repair with artificial neochordae (now preferred in 97% of cases since 2011) 6
- Annuloplasty ring placement (essential in all cases)
- Sliding leaflet valvuloplasty for excess posterior leaflet tissue 1
The median number of artificial chordae needed is substantial: 2 pairs for the anterior leaflet and 4 pairs for the posterior leaflet 6.
Outcomes
When performed by experienced surgeons, repair of Barlow disease achieves: