Description

A bicuspid aortic valve (BAV) is an abnormal formation of the aortic valve that contains two valve leaflets instead of the usual three. This is caused by abnormal formation of the aortic valve leaflets during embryologic development. This abnormal formation is often accompanied by abnormalities in the cellular structure of the aorta that result in aortic diameters that are larger, and increase in size more rapidly, than the general population (1).

Epidemiology

Incidence
Incidence is difficult to determine because this is a congenital condition that is often undiagnosed with unknown genetic transmission (1).

Prevalence
0.5–2% of the population are thought to be affected, making this the most common congenital heart defect in the adult population (1).

Etiology and Pathophysiology

Multiple genes have been implicated to include NOTCH1, ACTA2, and ubiquitin fusion degradation. These mutations lead, via an unknown mechanism, to abnormal fusion of two of the three aortic valve leaflets. This abnormal fusion has also been associated with decreased fibrillin, elastin fragmentation, and apoptosis in the aorta. These cellular changes are thought to also be responsible for the aortopathy that is often found in individuals with BAV. This aortopathy includes larger aortic diameter at baseline, increased speed of dilation of the aorta, and an associated increase risk of aortic dissection (1).

Genetics
There is a non-Mendelian inheritance pattern. There is a 9% incidence of BAV in first-degree relatives of those with BAV. This increases to 20% if >1 family member has BAV. Up to 30% of family members of an affected individual may have either a BAV or aortopathy (1,2,3).

Risk Factors

• Those with a first-degree relative with BAV (1,2)
• Males are 3 times more likely than females to be affected (1).

General Prevention

There are no known preventive measures.

Commonly Associated Conditions

• Common associations
  • Aortic stenosis: Up to 75% of patients may develop clinically significant disease as they age (2).
  • Bicuspid aortopathy: found in about 50% of patients with BAV (4)
  • Aortic incompetence/regurgitation: One study found 40% of patients that did not have aortic stenosis did have moderate to severe aortic disease (2).
  • Coarctation of the aorta occurs in 20–85% of cases (2).
• Rare associations
  • Infective endocarditis: incidence of 0.3–2% per year
  • Hypoplastic left heart syndrome
  • Shone syndrome
  • Turner syndrome
  • Ventricular septal defect
  • Patent ductus arteriosus
  • Atrial septal defect