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Bicuspid aortic valve (familial)
This condition can affect the heart's ability to pump blood effectively, potentially leading to complications over time. It can run in families, meaning there's often a genetic component that increases risk.
Overview
The aortic valve is a crucial component of the heart, controlling blood flow from the heart's main pumping chamber (left ventricle) into the aorta, the large artery supplying oxygenated blood to the body. Normally, this valve has three small flaps or 'leaflets' that open and close to ensure blood flows in one direction. In familial bicuspid aortic valve (BAV), the valve is formed with only two leaflets. This is the most common congenital heart anomaly, affecting approximately 1-2% of the general population [PMID:33675037].
While some individuals with BAV may live without significant problems, the altered structure can lead to the valve narrowing (stenosis) or leaking (regurgitation) over time. These issues can place extra strain on the heart, potentially leading to further complications. BAV often has a familial link, suggesting a genetic predisposition among affected individuals and their relatives.
Symptoms & clinical features
Individuals with bicuspid aortic valve may not experience any symptoms, particularly when they are younger. Often, the condition is discovered incidentally during a physical examination when a doctor hears a heart murmur, or during imaging for other reasons. Symptoms, if they develop, typically arise later in life, often in adulthood, as the valve dysfunction progresses.
When symptoms do occur, they can include breathlessness, particularly during physical activity, chest pain, dizziness or fainting spells, and unusual tiredness. These symptoms are usually related to either the aortic valve not opening wide enough (aortic stenosis), making the heart work harder to pump blood, or not closing tightly enough (aortic regurgitation), causing blood to leak backwards. Complications like aortic aneurysm, a bulging in the aorta, are also more common in individuals with BAV, which can also be asymptomatic until it becomes severe [PMID:30138409].
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Affected organs
The primary organ affected by familial bicuspid aortic valve is the heart, specifically the aortic valve. The altered structure of the valve can lead to impaired blood flow, either by narrowing the opening or allowing blood to leak backwards. Over time, this can cause the heart muscle to thicken or enlarge, affecting its ability to pump blood efficiently.
The aorta, the body's main artery that carries blood from the heart, is also frequently affected. Individuals with BAV have an increased risk of developing an aortic aneurysm, which is a weakening and bulging of the aortic wall, or aortic dissection, a serious tear in the arterial wall. These aortic problems can occur independently of the severity of the valve dysfunction.
Risks & severity
The severity of familial bicuspid aortic valve can vary considerably between individuals. Many people never develop significant complications and may not even know they have the condition. Others may experience progressive valve dysfunction, primarily aortic stenosis (narrowing) or regurgitation (leaking), sometimes requiring medical intervention.
Complications such as aortic dilation (enlargement) or aneurysm are observed more frequently in individuals with BAV compared to the general population. The lifetime risk of needing valve surgery or surgery for aortic complications is significantly higher for those with BAV. Regular monitoring is therefore important. The condition is congenital, meaning it is present from birth, but the clinical impact often becomes apparent in adulthood [PMID:33675037].
Genetic causes
While bicuspid aortic valve is largely sporadic, a significant proportion of cases, particularly those that run in families, have a genetic basis. Pathogenic changes in genes involved in heart development are thought to contribute to its occurrence. One gene that has been studied in relation to familial BAV is NOTCH1.
NOTCH1 provides instructions for making a protein that is vital for normal embryonic development, including the formation of the heart valves. The NOTCH1 signalling pathway plays a critical role in cell communication and differentiation. When there are specific changes (variants) in the NOTCH1 gene, this can disrupt the normal development process of the aortic valve leaflets, leading to the bicuspid structure. BAV can be genetically heterogeneous, meaning that other genes and environmental factors are also likely to play a role.
- NOTCH1 notch receptor 1
Inheritance pattern
Familial bicuspid aortic valve is typically inherited in an autosomal dominant pattern. This means that a person only needs to inherit one copy of an altered gene (such as NOTCH1) from one parent to be at an increased risk of developing the condition. If a parent has an autosomal dominant condition, there is a 50% chance with each pregnancy that their child will inherit the genetic alteration.
However, it's important to understand that having the genetic alteration does not guarantee that an individual will develop significant symptoms or complications. This concept is known as variable expressivity, meaning that even within the same family, some individuals with the same genetic change may have mild or no symptoms, while others may experience more significant health issues related to their bicuspid aortic valve.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of bicuspid aortic valve typically begins with a clinical suspicion, often after a doctor detects a heart murmur during a routine examination. The definitive diagnosis is usually made through non-invasive imaging. An echocardiogram, which uses sound waves to create images of the heart, is the primary diagnostic tool, allowing visualisation of the valve's structure and function.
Genetic testing for familial bicuspid aortic valve, particularly for genes like NOTCH1, is available and usually considered if there is a strong family history, or in more complex cases. Referrals for genetic testing in the UK often originate from a clinical genetics service or cardiology department, which can be accessed via an NHS R-code following relevant clinical guidelines. A clinical geneticist or a genetic counsellor will discuss the implications of genetic testing and potential results.
Management & lifestyle
Managing familial bicuspid aortic valve focuses on monitoring the valve and aorta, addressing complications as they arise, and preventing further issues. Regular follow-up appointments with a cardiologist are essential, typically involving repeat echocardiograms to assess valve function and aortic dimensions over time. Lifestyle modifications, such as maintaining a healthy weight, controlling blood pressure, and avoiding smoking, are generally recommended.
If the valve dysfunction becomes severe (e.g., significant stenosis or regurgitation) or if there is substantial enlargement of the aorta, surgical intervention may be necessary. This could involve repairing or replacing the aortic valve, or repairing the aorta. These decisions are made by a multidisciplinary team based on regular monitoring results and current clinical guidelines. Patients are encouraged to discuss their specific management plan with their cardiologist and general practitioner.
UK care pathway
In the UK, individuals suspected of having or diagnosed with bicuspid aortic valve (familial) are typically managed within NHS cardiology services. Following initial diagnosis, often through echocardiography, ongoing surveillance will be coordinated by a consultant cardiologist. For cases with a strong family history or consideration of genetic testing, referral to a clinical genetics service is appropriate. These referrals can be made by various healthcare professionals, with genetic testing pathways often underpinned by NHS England's Genomic Medicine Service (GMS) and relevant PanelApp R-codes. Genetic counsellors play a vital role in providing information and support to individuals and families regarding inheritance patterns and testing options.
Frequently asked questions
What is the likelihood of my children inheriting bicuspid aortic valve if I have it?
Familial bicuspid aortic valve is typically inherited in an autosomal dominant pattern. This means there is a 50% chance, for each child, to inherit the genetic predisposition. However, not everyone who inherits the genetic change will develop the condition or experience severe symptoms.
Do I need regular check-ups if I have bicuspid aortic valve but no symptoms?
Yes, even if you don't have symptoms, regular check-ups with a cardiologist are typically recommended. This allows for monitoring of your aortic valve's function and the size of your aorta, helping to detect any potential complications early.
What activities should I avoid if I have familial bicuspid aortic valve?
Your cardiologist will provide personalised advice regarding physical activity. Generally, most individuals can lead active lives. However, depending on the severity of your valve condition or if you have an enlarged aorta, certain strenuous activities or contact sports might be advised against to reduce risks.
Can bicuspid aortic valve be treated with medication?
Medication cannot change the structure of a bicuspid aortic valve itself. However, medicines may be used to manage associated conditions like high blood pressure, or to address symptoms such as breathlessness or chest pain, thereby helping to protect the heart and reduce strain. Surgery is typically considered if valve dysfunction or aortic enlargement becomes severe.
Is bicuspid aortic valve always inherited, or can it occur spontaneously?
While familial bicuspid aortic valve refers to cases with a genetic link, many instances of BAV occur spontaneously without a clear family history. It is believed to be a complex condition influenced by both genetic and environmental factors, and further research is ongoing to fully understand its causes.