Bicuspid aortic valve
|Bicuspid aortic valve|
|Classification and external resources|
A bicuspid aortic valve (BAV) is most commonly a congenital condition of the aortic valve where two of the aortic valvular leaflets fuse during development resulting in a valve that is bicuspid instead of the normal tricuspid configuration. Normally the only cardiac valve that is bicuspid is the mitral valve (bicuspid valve) which is situated between the left atrium and left ventricle. Cardiac valves play a crucial role in ensuring the unidirectional flow of blood from the atrium to the ventricles, or the ventricle to the aorta or pulmonary trunk.
Bicuspid aortic valves are the most common cardiac valvular anomaly, occurring in 1–2% of the general population. It is twice as common in males as in females.
Bicuspid aortic valve is an inheritable condition, with a demonstrated association with Notch 1. Its heritability () is as high as 89%. Both familial clustering and isolated valve defects have been documented. The incidence of bicuspid aortic valve can be as high as 10% in families affected with the valve problem. Recent studies suggest that BAV is an autosomal dominant condition with incomplete penetrance. Other congenital heart defects are associated with bicuspid aortic valve at various frequencies, including coarctation of the aorta.
Bicuspid aortic valves may assume three different types of configuration:
- "Real" bicuspid valves with two symmetric leaflets
- A tricuspid architecture with a fusion of two leaflets
- A tricuspid architecture with a fusion of three leaflets
In many cases, a bicuspid aortic valve will cause no problems. However BAV may become calcified later in life, which may lead to varying degrees of severity of aortic stenosis that will manifest as murmurs. If the leaflets do not close correctly, aortic regurgitation can occur. If these become severe enough, they may require heart surgery. People with BAV may become tired more easily than those with normal valvular function and have difficulty maintaining stamina for cardio-intensive activities-due to poor heart performance. The heart is put under more stress in order to either pump more blood through a stenotic valve or attempt to circulate regurgitation blood through a leaking valve.
Diagnosis, treatment, and prognosis
The condition can be associated with a heart murmur located at the right second intercostal space. Often there will be differences in blood pressures between upper and lower extremities. The diagnosis can be assisted with echocardiography (EchoCG) or magnetic resonance imaging (MRI).
Most patients with bicuspid aortic valve whose valve becomes dysfunctional will need careful follow-up and potentially valve replacement at some point in life. Regular EchoCG and MRI may be performed. For diagnosed patients, genetic testing is done to allow for future offspring with the disease to be monitored and treated early in life.
Patients with bicuspid aortic valve should be followed by a cardiologist or cardiac surgeon with specific interest in this valve pathology.
If the valve is normally functioning or minimally dysfunctional, average lifespan is similar to that of those without the anomaly.
One of the most notable associations with BAV is the tendency for these patients to present with ascending aortic aneurysmal lesions. The extracellular matrix of the aorta in patients with BAV shows marked deviations from that of the normal tricuspid aortic valve. It is currently believed that an increase in the ratio of MMP2 (Matrix Metalloproteinases 2) to TIMP1 (Tissue Inhibitor Metalloproteinases 1) may be responsible for the abnormal degradation of the valve matrix and therefore lead to aortic dissection and aneurysm. However, other studies have also shown MMP9 involvement with no differences in TIMP expression. The size of the proximal aorta should be evaluated carefully during the work-up. The initial diameter of the aorta should be noted and annual evaluation with CT scan, or MRI to avoid ionizing radiation, should be recommended to the patient; the examination should be conducted more frequently if a change in aortic diameter is seen. From this monitoring, the type of surgery that should be offered to the patient can be determined based on the change in size of the aorta.
Co-arctation of the aorta (a congenital narrowing in the region of the ductus arteriosus) has also been associated with BAV.
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- Rison, SC; Locke, TP; Rosenthal, E; Gandhi, S (2012 Feb 15). "A man with hypertension and two murmurs.". BMJ (Clinical research ed.) 344: e956. PMID 22337753.
- Bicuspid Aortic Foundation Homepage
- Cedars Sinai Heart Center - Bicuspid Aortic Disease
- Bicuspid Aortic Valve Discussion Board