What is Bicuspid Aortic Valve?
A bicuspid aortic valve is the most common birth defect of the heart, found in about 1% of all people. It’s more common in males than in females, with a ratio of 2 to 1. Having a bicuspid aortic valve can cause the valve to wear out over time and often coincides with a dilation or enlargement of the ascending aorta, the large blood vessel branching off the heart.
What Causes Bicuspid Aortic Valve?
The bicuspid aortic valve, a condition where the aortic valve in the heart has two leaflets instead of the typical three, can occur sporadically or can run in families. Research shows that when this condition is inherited in families, the pattern can vary but is often dominant, meaning a child can inherit it if just one parent passes it down. It is also found that nearly 20% to 30% of family members might also have a bicuspid aortic valve.
The exact reason why someone might develop a bicuspid aortic valve is still not completely understood. There are several theories about how it might occur. One idea is that if blood doesn’t flow normally across the valve when it’s developing, the valve might not separate properly. Another theory suggests that the issue might occur when there are disruptions in the movement of nerve-related cells that can result in the merging of the parts of a valve. It’s also been suggested that the condition might be caused by a lack of a certain compound called endothelial nitric oxide synthetase, which helps maintain the health of blood vessels.
Risk Factors and Frequency for Bicuspid Aortic Valve
The bicuspid aortic valve affects 1-2% of the general population. With the introduction of echocardiography, more cases are being detected. Half to three-fourths of patients with coarctation of the aorta, a heart condition, also have a bicuspid aortic valve. The condition is also common in certain syndromes. Here are some examples:
- 30% of people with Turner syndrome have a bicuspid aortic valve.
- 30% of William syndrome and ventricular septal defect cases are associated with a bicuspid aortic valve.
- It’s also found in rare syndromes like Shone syndrome.
Signs and Symptoms of Bicuspid Aortic Valve
A bicuspid valve’s appearance can change depending on how narrow or inadequate the valve is. In children, the mildest form often comes without symptoms or signs of a faulty valve. In this case, the physical check-up might reveal a low, soft whooshing sound during the heart’s contraction phase and an ejection click. Younger patients often have this ejection sound followed by the same type of low whooshing sound. If the valve flaps become stiffer and move less, these ejection sounds may be less noticeable. The test results also depend on how seriously the valve is failing. With mild to moderate backflow through the aortic valve, the ejection sound remains. However, when the backflow is severe, this sound is usually absent.
Testing for Bicuspid Aortic Valve
In order to evaluate a bicuspid valve, which is a valve in your heart that only has two flaps instead of the usual three, doctors mainly use two methods: an electrocardiogram and echocardiogram. The electrocardiogram is a test that measures the electrical activity of your heart, and if the bicuspid valve is severely narrow (a condition known as stenosis), this test might show that the left side of your heart is unusually thick and that the electrical patterns in your heart are unusual.
An echocardiogram, frequently used to learn more about how a bicuspid aortic valve looks and functions, uses sound waves to create detailed images of your heart. By using 2D echocardiography, doctors can observe the specific features of the valve such as the fusion of the leaflets (parts) of the valve, and how the valve closes. This method is reliable but when the valve has a lot of calcium build-up this might be hard to visualize. With this technique, doctors can also measure the size of the part of your aorta that is near your heart.
Doppler echocardiography, a special type of echocardiogram, can provide information about whether the bicuspid valve has become narrowed (stenosis) or leaky (insufficiency). While it is unusual, at times doctors may need to measure the pressure in your heart directly using a special procedure known as cardiac catheterization, but they usually only do this when they are planning a procedure that is meant to fix the valve. Imaging tests like CT scans or MRIs can also provide additional details about your aorta, for instance, it can help doctors measure the aorta’s size more accurately.
In terms of diagnosing a bicuspid aortic valve, 2D echocardiography is pretty reliable – it’s correct about 93% of the time, it correctly identifies the valve as bicuspid about 96% of the time, and it can detect the condition in the first place about 78% of the time.
Treatment Options for Bicuspid Aortic Valve
If you have a healthily functioning bicuspid aortic valve, you should have regular check-ups. It’s important to be aware that this type of valve will naturally wear down over time, and at present, there’s no treatment available to slow this process. In simple terms, a bicuspid aortic valve is a valve in the heart with two leaflets (or flaps) instead of the usual three. This condition can lead to your valve becoming narrower (aortic stenosis) or not closing properly (aortic regurgitation).
Immediate family members of patients with a bicuspid aortic valve and aortopathy, a disease affecting the aorta, should get screened. However, it’s not necessary for all family members to be screened. When a patient is known to have a bicuspid aortic valve, a type of heart scan called a transthoracic echocardiography is required. This scan helps check the structure of the valve, if there’s stenosis or regurgitation, and also measures the size of the aortic sinuses (the sacs in the walls of the aorta) and the ascending aorta (the part of the aorta that rises from the heart).
If a patient with a bicuspid aortic valve has an ascending aorta measuring 4 cm in diameter, they should regularly be checked using echocardiography. If echocardiography can’t visualise it properly, then angiographies, which are special types of X-ray, either using MRI or CT scan, would be used. If the size increases to over 4.5 cm, an annual echocardiography exam is recommended according to the American Heart Association.
In kids, surgery may be needed under certain conditions, such as if there are certain changes in their EKG readings (a non-painful test that records the heart’s electrical activity), or if they want to be athletes. The preferred surgical procedure in kids is valvuloplasty, which is a method of enlarging a narrow heart valve.
For adults over 18 years old with a bicuspid aortic valve, the need for having a valve replacement is the same as those with a tricuspid aortic valve. However, as this population tends to be younger than those with tricuspid aortic valves and often need additional operations on their aortic sinuses or ascending aorta, deciding on the type of replacement valve can be a bit challenging. According to current American Heart Association guidelines, if a surgeon is performing a valve replacement and realizes that the root of the aorta is larger than 4.5 cm, they should replace the aortic root during the same surgery.
What else can Bicuspid Aortic Valve be?
The following are several different medical conditions related to heart disease in children:
- Coarctation of the aorta
- Interrupted aortic arch
- Pediatric aortic arch insufficiency
- Pediatric Ebstein anomaly
- Pediatric mitral valve prolapse
- Pediatric rheumatic heart disease
- Pediatric sub valvar aortic stenosis
- Turner syndrome
- Valvar pulmonary stenosis
- Williams syndrome
Possible Complications When Diagnosed with Bicuspid Aortic Valve
A bicuspid aortic valve can cause significant issues with your heart’s function. Specifically, this can result in conditions called aortic stenosis or aortic regurgitation. This valve issue also makes it more likely to develop an infectious heart disease known as infective endocarditis.
Additionally, a bicuspid aortic valve is often linked to:
- Aorta narrowing, known as coarctation of the aorta
- Expansion of the aorta, with 40% to 60% of people experiencing what is known as ascending aortic dilatation
- Aortic aneurysm, a serious condition in which the aorta’s wall weakens and bulges
