Brugada syndrome (SCN5A): inherited heart rhythm condition

Brugada syndrome is a channelopathy: a disorder of the tiny channels that let electrically charged particles in and out of heart cells. It can trigger a fast, chaotic rhythm from the lower chambers of an otherwise structurally normal heart. The NHS describes it as a rare condition that is usually inherited and can be life-threatening, but says there are things to do to reduce the risk of serious problems.

The NHS says it does not usually cause any symptoms and is sometimes found when an ECG is done for another reason. When symptoms occur they can include fainting or blackouts, dizziness, palpitations, seizures or breathlessness, and they usually start in adulthood, although they can occur at any age. The NHS Genomics Education Programme says the first presentation is commonly around 40 and that dangerous rhythms often happen during sleep.

A cardiologist makes the diagnosis from a characteristic ECG called the type 1 Brugada pattern. If this appears spontaneously at rest, the diagnosis can be made. If it appears only with a fever, or after a drug called ajmaline is given through a drip during an ECG (the NHS calls this a provocation test), other features, such as a dangerous rhythm, a faint caused by an arrhythmia or a relevant family history, are needed to make the diagnosis, according to the NHS Genomics Education Programme.

The programme notes that after a sudden death in which no cause is found, the diagnosis can sometimes be made through a molecular autopsy, which has implications for the whole family.

SCN5A encodes part of the sodium channel in the heart, and it is also linked to long QT syndrome type 3 and to progressive cardiac conduction disease. Even so, the NHS Genomics Education Programme says that most people with Brugada syndrome do not have a single disease-causing gene variant identified, and up to 20% have a pathogenic change in SCN5A. Research suggests variants in other genes matter too, and in some families the pattern may be polygenic.

Where a variant is found it usually follows an autosomal dominant pattern, so each child of an affected parent has a 1 in 2 chance of inheriting it. Variants can also arise new in the person, and incomplete penetrance means not everyone with a variant develops the condition. Because of this variability, members of the same family can show different features from the same gene change, described as overlap syndromes.

Men and women inherit the variants equally, but the NHS says Brugada syndrome is more common in men and in people of South East Asian origin, and the programme says the condition appears to affect men more frequently.

The NHS says that people with Brugada syndrome who have had no symptoms will not usually need medical treatment, as most have a low risk of serious problems, and are monitored regularly. A defibrillator (ICD) is only needed if there have been symptoms such as cardiac arrest, palpitations or fainting, or doctors think the risk of a dangerous rhythm is high. The NHS Genomics Education Programme adds that an ICD is recommended after a survived cardiac arrest or documented spontaneous ventricular arrhythmia, may be considered with a spontaneous type 1 pattern and fainting, and that asymptomatic people may have electrophysiology studies. Quinidine or catheter ablation can be used for recurrent arrhythmias.

• Treat a fever promptly with paracetamol or ibuprofen. The NHS advises getting help from NHS 111 if a high temperature does not go down.

• Keep drinks up and use oral rehydration solution during vomiting or diarrhoea.

• Avoid excess alcohol: the NHS says no more than 14 units a week, spread over 3 days or more. Avoid cocaine; the NHS Genomics Education Programme also advises avoiding cannabis and large meals before bed.

• Check every new medicine with a doctor or pharmacist; the programme refers to the BrugadaDrugs.org list of medicines to avoid.

• Avoid very strenuous exercise or sport (NHS advice).

• Call 999 if someone is not breathing normally and unresponsive, is having a seizure, or has fainted and cannot be woken within 1 minute.

The NHS says that if you are diagnosed your immediate family should be offered testing, and that you should ask for an urgent GP appointment if a parent, child, brother or sister has been diagnosed or died unexpectedly. The NHS Genomics Education Programme recommends clinical screening with genomic testing where appropriate for all first-degree relatives, in a specialist inherited cardiac conditions clinic because of the complexity of inheritance.

Your care team passes information to the National Congenital Anomaly and Rare Disease Registration Service, from which you can opt out at any time, according to the NHS. Support is available from the British Heart Foundation and Cardiac Risk in the Young.