Brugada syndrome
Genetic disorder increasing risk of abnormal heart rhythms and sudden death.
Brugada syndrome is a genetic condition that disrupts the heart's normal electrical signaling, a problem known as a channelopathy. This disruption raises the risk of dangerous heart rhythms and sudden cardiac death. People with the syndrome may experience fainting spells. The abnormal rhythms often happen when the person is at rest and can be set off by a fever.
The condition was first documented in 1989 by Andrea Nava and Bortolo Martini in Padova. It gets its name from Spanish cardiologists Pedro and Josep Brugada, who described it in 1992. Chen Qiuyun was the first to identify the genetic abnormality in the SCN5A channel.
**Signs and symptoms** Many individuals with Brugada syndrome have no symptoms at all. However, the syndrome can cause fainting or sudden cardiac death from serious arrhythmias like ventricular fibrillation or polymorphic ventricular tachycardia. Brief episodes of abnormal rhythm that correct themselves may lead to blackouts. If a dangerous rhythm doesn't stop on its own and goes untreated, it can result in a fatal cardiac arrest. Blackouts can also occur even with a normal heart rhythm due to a sudden drop in blood pressure, known as vasovagal syncope. The abnormal rhythms are most common at rest, after a heavy meal, or during sleep—times when the vagus nerve is highly active, or periods of high vagal tone. Fever and heavy alcohol use can also trigger these rhythms. Sodium-channel-blocking drugs, often used to treat other heart rhythm problems, can worsen the tendency toward dangerous rhythms and should be avoided.
**Causes** In Brugada syndrome, the electrical signals that heart muscle cells use to communicate are disrupted. As a genetic disorder, it stems from changes in a person's DNA. The first mutations linked to the syndrome were found in a gene that controls a protein, or ion channel, responsible for the flow of sodium ions through heart cell membranes—the cardiac sodium channel. Most later-discovered mutations also affect the sodium current or other ionic currents. A variety of factors can produce a Brugada-like ECG pattern, including certain medications, electrolyte imbalances like low potassium levels, and reduced blood supply to the right ventricular outflow tract.
Quick Facts
- Field
- Cardiology
- Symptoms
- Passing out, sudden cardiac death
- Onset
- Adulthood
- Causes
- Genetics, certain medication
- Risks
- Family history, Asian descent, male
- Diagnosis
- Electrocardiogram (ECG), genetic testing
- Differential
- Romano-Ward syndrome, arrhythmogenic cardiomyopathy, Duchenne muscular dystrophy
- Treatment
- Watchful waiting, implantable cardioverter defibrillator (ICD)
- Frequency
- 1 per 2000
- Deaths
- 8% of sudden cardiac death
Facts from the source article.
Lore & Background
Brugada syndrome is a genetic condition in which the electrical activity of the heart is abnormal due to channelopathy. It increases the risk of abnormal heart rhythms and sudden cardiac death. Those affected may have episodes of syncope. The abnormal heart rhythms often occur at rest, and may be triggered by a fever. About a quarter of those with Brugada syndrome have a family member who also has the condition. Some cases may be due to a new genetic mutation or certain medications. The most commonly involved gene is SCN5A which encodes the cardiac sodium channel. Diagnosis is typically by electrocardiogram (ECG), however, the abnormalities may not be consistently present. Medications such as ajmaline may be used to reveal the ECG changes. Similar ECG patterns may be seen in certain electrolyte disturbances or when the blood supply to the heart has been reduced.
Reader's Guide
Brugada syndrome is significant as a leading cause of sudden cardiac death in young adults, particularly in males and those of Asian descent. It affects between 1 and 30 per 10,000 people. The condition is inherited in an autosomal dominant manner, but only 20% of cases are associated with mutations in SCN5A. The genetics are complex, with over 290 mutations in SCN5A discovered, and variable penetrance means some family members carrying a mutation may not show the condition. There is no cure; treatment for those at higher risk includes an implantable cardioverter defibrillator (ICD). Isoproterenol may be used short-term for frequent life-threatening arrhythmias, while quinidine may be used longer term. The condition highlights the importance of genetic testing and family screening. Its legacy includes ongoing research into the mechanisms of arrhythmias, including the role of sodium current and vagal tone, and the need for careful avoidance of sodium-channel-blocking medications.
Did You Know?
- The abnormal heart rhythms in Brugada syndrome often occur at rest, after a heavy meal, during sleep, or with fever.
- The condition is more common in males than females and in those of Asian descent.
- Medications such as ajmaline may be used to reveal ECG changes that are not consistently present.
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