Unicuspid Aortic Valve as a Variant of Bicuspid Aortic Valve
Yes, unicuspid aortic valve (UAV) should be considered an extreme variant in the spectrum of bicuspid aortic valve (BAV) syndromes, with similar baseline characteristics but more accelerated valve degeneration and stenosis. 1
Definition and Classification
- UAV is a rare congenital aortic valve anomaly that has two subtypes: unicommissural and acommissural 2
- BAV is the most common congenital cardiac malformation affecting 1-2% of the population, while UAV is much rarer 3
- Both conditions represent abnormal valve development with reduced number of cusps compared to the normal tricuspid aortic valve 4
Evidence Supporting UAV as a BAV Variant
The GenTAC Registry comparison found that UAV and BAV patients share similar:
- Baseline characteristics
- Demographics
- Clinical findings
- Family history patterns of BAV and aortic aneurysm/coarctation
- Patterns of aortic dimensions and enlargement of the ascending aorta 1
The key difference is that aortic stenosis is more common and severe in UAV patients, with:
- Higher mean and peak gradients
- Smaller aortic valve areas
- More advanced valvular degeneration 1
Morphological Considerations
- BAV typically results from fusion of two cusps (most commonly right and left coronary cusps), creating a valve with two functional cusps 4
- UAV represents a more extreme fusion pattern, resulting in a single functional cusp 2
- Both conditions can have raphe (ridge of tissue at site of fusion) that can make differentiation challenging 5
Clinical Implications
Both BAV and UAV are associated with:
- Aortic valve dysfunction (stenosis or regurgitation)
- Thoracic aortic dilatation and aneurysm formation
- Risk of aortic dissection 4
UAV patients typically present with symptoms at a younger age due to more rapid valve degeneration 6, 1
Management recommendations for BAV can reasonably be applied to UAV patients given their similar underlying pathophysiology 1
Diagnostic Challenges
Distinguishing UAV from BAV can be challenging, especially when calcification is present 4, 5
Echocardiographic criteria for UAV diagnosis include:
- Single commissural attachment zone
- Rounded, leaflet-free edge opposite to commissural attachment
- Eccentric valvular orifice during systole
- Young patient age with elevated transvalvular gradient 5
Multi-modality imaging is often necessary for accurate diagnosis 2
Management Considerations
All patients with abnormal aortic valve morphology (BAV or UAV) should have both the aortic root and ascending thoracic aorta evaluated for evidence of aortic dilatation 4
First-degree relatives of patients with BAV or UAV should be evaluated for the presence of abnormal valve morphology and asymptomatic thoracic aortic disease 4
Patients with BAV or UAV have increased risk of aortic dissection, even at smaller aortic diameters, similar to patients with Marfan syndrome 4
Treatment options for UAV include balloon valvuloplasty, surgical valvotomy, Ross procedure, valve repair, or replacement depending on patient age and valve pathology 2, 6