Bicuspid aortic valve (BCAV) is one of the common congenital abnormality of heart . Incidence can be 1-2% of population . It can result in premature aortic degeneration with Aortic stenosis/Aortic regurgitation or both .
The normal development and arrangement of three cusps is altered ( rather interrupted ) during fetal life.
There can be two ways BCAV can occur. One is due to the fusion* of two leaflets to covert a tricuspid valve into bicuspid , and the other is two cusps develop de novo .The former has a raphe , while the later has no raphe.
The fusion* occurs between either
- Right and left (R +L)
- Right and non coronary cusp (R +N )
- or Left and Non coronary cusp (L +N)
(* The fusion is embryological , not acquired )
Most often the fusion is due to lack of division in the valve analgen .Hence a raphe (A conjoint remnant) is noticed .
90% of BCAV has raphe ,only 10 % lack raphe . Aortic root is also structurally abnormal in many .(Little clinical sequale though !)
Coronary artery origin anomalies are more common with BCAV. We also know co-arctation of aorta has a embryological link with BCAV.
The commonest type of BCAV is
The most hemodyanmic stressed BCAV is R +N type fortunately it is rare
The least common type is
BCAV in the absence of raphe is classified separately (This constitutes 10 % of all BCAV)
The nomenclature is
- Antero posterior (Common type ) AP
- Lateral (L )
What is the pathological significance of raphe ?
Many believe presence of raphe accelerates degeneration as leaflets have rough surfaces . Still , BCAV with raphe has less coronary anomalies and aortic root pathology .
Presence of raphe indicate relatively a minor embryological defect , as the fault is in the failure to divide after the formation of analgen , while BCAV without raphe imply lack of development of analgen itself . This is expressed in the coronary sinus anatomy and aortic root dimension and orientation .
So currently it is welcome to spot a raphe in the patient point of view .Echo cardiogram is notoriously unreliable to diagnose raphe. Once degeneration process sets in , it is almost impossible to recognize the presence or absence of raphe .
* Please note ,tricsupid aortic valve with eccentric leaflet closure shares a close pathological relationship with BCAV. Premature degeneration , (AR more common than AS here ) .This entity will be discussed separately later.
Part of the Image (The valve) is adopted from Yale university Image Bank .