What is the appearance of a bicuspid aortic valve in a 2D (two-dimensional) echo?

Echocardiographic Appearance of Bicuspid Aortic Valve in 2D Echo

The diagnosis of a bicuspid aortic valve (BAV) is most reliable when two cusps are seen in systole with only two commissures framing an elliptical systolic orifice in the short-axis view. 1

Key Diagnostic Features

Short-Axis View (Primary Diagnostic View)

• Most reliable view for BAV diagnosis, showing:
  • Two cusps in systole instead of three 1
  • Only two commissures visible 1
  • Elliptical systolic orifice (oval-shaped) rather than triangular or stellate 1
  • Increased orifice aspect ratio (1.44 ± 0.11 vs. 1.10 ± 0.13 in normal tricuspid valves) 2

Diastolic Appearance

• May mimic three cusps when a raphe (fusion ridge) is present 1
• Raphe represents the fusion line between two cusps and can be mistaken for a commissure 1

Long-Axis View (Supporting Features)

• May show asymmetric closure line 1
• Systolic doming of the valve leaflets 1, 3
• Diastolic prolapse of one or both cusps may be visible 1
• These findings are less specific than short-axis systolic images 1

BAV Morphological Types

Type 1: Right and Left Coronary Cusp Fusion (Most Common)

• Accounts for approximately 80% of BAV cases 1, 4
• Results in larger anterior and smaller posterior cusp 1
• Both coronary arteries typically arise from the anterior cusp 1

Type 2: Right and Non-Coronary Cusp Fusion

• Accounts for approximately 20% of BAV cases 1, 4
• Results in larger right than left cusp 1
• One coronary artery arises from each cusp 1

Type 3: Left and Non-Coronary Cusp Fusion

• Rare morphology 1, 4

True Bicuspid Valve

• Two equally sized cusps without raphe 1
• Rare variant 1

Diagnostic Challenges

• In adults, stenosis of BAV typically results from superimposed calcific changes 1
• Extensive calcification often obscures the number of cusps, making determination of bicuspid vs. tricuspid valve difficult 1, 5
• Technical limitations may prevent adequate imaging of valve leaflets in many patients 5
• Diagnostic accuracy is higher in younger patients with less calcification 5

Associated Findings

• Geometry and dilatation of the aortic root and ascending aorta may provide indirect hints of BAV presence 1, 4
• Type 1 BAV is associated with larger aortic sinuses 4
• Type 2 BAV is associated with larger arch dimensions and ascending aorta dilatation 4
• Increased transvalvular peak velocity compared to normal tricuspid valves 2
• Increased maximum ascending aortic wall shear stress 2

Diagnostic Accuracy

• When images are adequate, 2D echocardiography has high sensitivity (78%) and specificity (96%) for BAV diagnosis 6
• 3D echocardiography can provide better visualization of valve morphology, showing the valve "en face" from the aortic perspective 1
• Transesophageal echocardiography (TOE) may be helpful when transthoracic image quality is suboptimal 1

Distinguishing from Other Valve Morphologies

• Tricuspid aortic valve: Shows three cusps with a stellate-shaped systolic orifice 1
• Unicuspid aortic valve: Extremely rare, considered a variant of BAV with more severe presentation 7
• Rheumatic aortic valve: Shows commissural fusion with a triangular systolic orifice and thickening/calcification along the edges of the cusps 1

By understanding these echocardiographic features, clinicians can more accurately identify bicuspid aortic valves, which is crucial for appropriate management and monitoring of associated complications.