Familial atrial fibrillation

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Familial atrial fibrillation is an inherited abnormality of the heart's normal rhythm. Atrial fibrillation is characterized by episodes of uncoordinated electrical activity (fibrillation) in the heart's upper chambers (the atria), which cause a fast and irregular heartbeat. If untreated, this abnormal heart rhythm (arrhythmia) can lead to dizziness, chest pain, a sensation of fluttering or pounding in the chest (palpitations), shortness of breath, or fainting (syncope). Atrial fibrillation also increases the risk of stroke and sudden death. Complications of atrial fibrillation can occur at any age, although some people with this heart condition never experience any health problems associated with the disorder.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Changes in some genes can cause atrial fibrillation on their own, while changes in other genes affect a person's risk of developing this condition in combination with a variety of environmental and lifestyle factors. Familial atrial fibrillation often results from rare mutations in single genes. However, these cases represent only a small fraction of all individuals with atrial fibrillation.

The first single gene found to be associated with familial atrial fibrillation was KCNQ1, which provides instructions for making a channel that is embedded in the outer membrane of heart (cardiac) muscle cells. This channel transports positively charged atoms (ions) of potassium out of cells. In cardiac muscle, this ion transport plays a critical role in maintaining the heart's normal rhythm. Since that discovery, rare genetic variants in other ion channel genes have been found to cause familial atrial fibrillation. Mutations in ion channel genes lead to the production of altered channels, which may either increase or decrease the flow of ions across the outer cell membrane and alter the way the heart beats.

Mutations in other types of genes have also been found to cause familial atrial fibrillation. Some of these genes provide instructions for making cardiac transcription factors, which regulate the activity of certain genes involved in the formation and development of the heart before birth. Other genes provide instructions for making parts of structural elements of cardiac muscle, such as sarcomeres. These structures are necessary for cardiac muscle to contract and produce the heart's pumping action. Mutations in these non-ion channel genes have a variety of effects on the structure and function of cardiac muscle, all of which can lead to an abnormal heartbeat.

Most cases of atrial fibrillation are not caused by inherited mutations in single genes. However, relatively common variations (polymorphisms) in more than two dozen genes appear to influence the likelihood of developing the condition. Each of these polymorphisms on its own has a small effect on a person's overall risk, but an individual may have multiple polymorphisms that together have a significant effect. In addition to these common genetic variations, risk factors for atrial fibrillation include high blood pressure (hypertension), diabetes mellitus, a previous stroke, or an accumulation of fatty deposits and scar-like tissue in the lining of the arteries (atherosclerosis). Researchers are working to determine how a combination of genetic changes, environmental influences, and lifestyle factors contribute to a person's risk of developing atrial fibrillation.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

When familial atrial fibrillation is caused by mutations in a single gene (such as KCNQ1), it is inherited in an autosomal dominant pattern. Autosomal dominant inheritance means that one copy of the altered gene in each cell is sufficient to cause the disorder. In these cases, an affected person inherits the mutation from a parent who has the condition.

Common genetic variants that increase the risk of atrial fibrillation can also be passed through generations in families. Individuals with these variants may have a family history of atrial fibrillation, but in these cases the condition does not have a clear autosomal dominant inheritance pattern.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Atrial fibrillation is the most common type of recurrent arrhythmia, affecting more than 3 million people in the United States. The risk of developing this irregular heart rhythm increases with age. The incidence of the familial form of atrial fibrillation is unknown; however, recent studies suggest that up to 30 percent of all people who have atrial fibrillation without an identified cause have a history of the condition in their family.

Which doctor should you see?

The suggested department for discussing Familial atrial fibrillation is Cardiology, with a cardiologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Is the main concern heart structure, rhythm, circulation or another cause?
• Which symptoms should change the timing of follow-up?
• How would a proposed investigation change the care plan?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.