Bicuspid Aortic Valve: Anatomy, Classification, and Associated Aortopathy
Anatomy of the Normal Aortic Valve
Normally, the aortic valve has three cusps: the right coronary cusp (RCC), the left coronary cusp, and the non-coronary cusp (NCC). Each cusp is associated with a sinus of Valsalva, a pouch-like structure located above the valve. The right coronary cusp is oriented towards the right coronary artery, the left towards the left coronary artery, and the non-coronary cusp is not associated with any coronary artery. At the center of the free edge of each cusp is the nodule of Arantius, ensuring tight valve closure.
Normally, the separation of the aortic valve cusps (the maximum distance between the cusps at the beginning of systole during maximum opening) is 15–26 mm. The normal aortic valve orifice area is at least 2 cm².
Features of Echocardiographic Visualization in BAV
In children and adolescents, a bicuspid valve may be stenotic without significant calcification. In adults, stenosis of the bicuspid aortic valve is usually due to superimposed calcific changes, which often obscure the number of cusps, making it difficult to distinguish between bicuspid and tricuspid valves.
In comparison, calcification of the tricuspid aortic valve is most pronounced at the central part of each cusp with no commissural fusion, leading to the formation of a star-shaped systolic orifice.
Classification of BAV and Aortopathy
According to the international consensus statement (Michelena HI, Corte AD, Evangelista A et al.), a unified nomenclature and classification of the congenital bicuspid aortic valve and its associated aortopathy have been developed for clinical, surgical, interventional, and research purposes. Specific types according to the Sievers classification and their threshold criteria are not provided in the given excerpts [clarify].
Technical Aspects of Doppler Assessment of Flow through AoV
The SAX BASE view is not optimal for assessing flow through the aortic valve because the flow is directed at an angle of about 90° relative to the plane of the ultrasound wave. For accurate Doppler assessment, views with maximum alignment to a Doppler angle of 0° should be selected.
Frequently asked questions
Why is it difficult to count the number of cusps in BAV in adults?
In adults, stenosis of the BAV is usually due to superimposed calcific changes, which obscure the number of cusps and make it difficult to distinguish between bicuspid and tricuspid valves.
Can BAV be stenotic without calcification?
Yes, in children and adolescents, a bicuspid valve can be stenotic without significant calcification.
Which international consensus is used for the classification of BAV?
The international consensus statement on the nomenclature and classification of the congenital bicuspid aortic valve and its aortopathy (Michelena HI et al.) for clinical, surgical, interventional, and research purposes.
Which view is not optimal for Doppler assessment of the aortic valve?
The SAX BASE view is not optimal because the flow through the aortic valve is directed at an angle of about 90° relative to the ultrasound wave.
What are the normal parameters for aortic valve opening?
The normal separation of the cusps is 15–26 mm, and the normal aortic valve orifice area is at least 2 cm².