A congenital heart defect is a malformation that has been present
since birth. The most common heart defect that causes
aortic valve stenosis is a bicuspid aortic valve. A
normal (tricuspid) aortic valve has three flaps, or leaflets; a bicuspid valve
has only two leaflets.
This abnormal valve structure causes rough, turbulent blood flow,
which over the years can lead to stenosis through the same degenerative process
that occurs in normal valves. The main difference is that someone who has a
bicuspid valve will typically develop stenosis in their 30s or 40s, as opposed
to people who have normal valves, who develop stenosis after age 50 or 60.
People who have a bicuspid valve are also more likely than other
people to get an infection (infective endocarditis) that can cause the aortic
valve to become leaky (aortic regurgitation) as well as narrow.
Two other, less common congenital defects can cause aortic valve
stenosis:
- A misshapen tricuspid aortic valve. Although the
valve has the correct number of leaflets, the leaflets may not all be the same
size.
- A unicuspid valve. This valve, which has only one leaflet,
can cause severe stenosis during infancy and may be fatal at an early age. A
unicuspid valve is the most common cause of death from aortic valve stenosis in
children younger than 1 year.