What is Brugada syndrome?
Brugada syndrome is a genetic disorder that can causes a dangerous irregular heartbeat. In many cases, a defect in the SCN5A gene causes the genetic form of this condition. When this defect occurs, it may cause a ventricular arrhythmia. This is a type of irregular heartbeat. When this happens, the lower chambers of your heart (ventricles) beat irregularly and prevent blood from circulating properly in your body. This can be dangerous and may result in fainting or even death, especially during sleep or rest. The disease has been known as sudden, unexplained nocturnal death syndrome because people with it can often die in their sleep.
Brugada syndrome is rare. It affects about 5 of every 10,000 people worldwide. Symptoms usually show up during adulthood, although the disorder can develop at any age, including infancy. The average age of death related to the disease is 40 years old.
Types of ECG in Brugada Syndrome
There are three types of ECG findings in Brugada syndrome patients:
Type I: Lead V1 has a “coved” ST segment elevation of at least 2 millimeters, followed by a negative T wave.
Type II: There is a “saddleback” appearance of the ST segment in lead V1 with ST segment elevation of at least 2 millimeters; this can be present in normal individuals as well.
Type III: Features of type I (coved) or type II (saddleback) with less than 2 millimeters of ST segment elevation.
Causes
It can run in families. About 30% of people who have it have a problem with a gene that helps their heart stay in normal rhythm. If you have a family member who has it, you may want to see your doctor to find out if you’re at risk for it too.
In other cases, doctors don’t know what causes it. Some possibilities include:
- Cocaine use
- High levels of calcium in your blood
- Medicines that treat high blood pressure, depression, or chest pain
- Very high or very low levels of potassium
Risk factors
There are a few risk factors for developing Brugada syndrome. These include:
- Family history. Since the mutations that cause Brugada syndrome can be inherited, if someone in your immediate family has it, you may have it as well.
- Although the condition can affect both males and females, it’s 8 to 10 timesTrusted Source more common in men than in women.
- Brugada syndrome appears to occur more frequently in people of Asian ancestry.
Pathophysiology
Brugada syndrome is an example of a channelopathy, a disease caused by an alteration in the transmembrane ion currents that together constitute the cardiac action potential. Specifically, in 10-30% of cases, mutations in the SCN5A gene, which encodes the cardiac voltage-gated sodium channel Nav 1.5, have been found. These loss-of-function mutations reduce the sodium current (INa) available during the phases 0 (upstroke) and 1 (early repolarization) of the cardiac action potential.
This decrease in INa is thought to affect the right ventricular endocardium differently from the epicardium. Thus, it underlies both the Brugada ECG pattern and the clinical manifestations of the Brugada syndrome.
The exact mechanisms underlying the ECG alterations and arrhythmogenesis in Brugada syndrome are disputed. The repolarization-defect theory is based on the fact that right ventricular epicardial cells display a more prominent notch in the action potential than endocardial cells. This is thought to be due to an increased contribution of the transient outward current (Ito) to the action potential waveform in that tissue.
A decrease in INa accentuates this difference, causing a voltage gradient during repolarization and the characteristic ST elevations on ECG. Research has provided human evidence for a repolarization gradient in patients with Brugada syndrome using simultaneous endocardial and epicardial unipolar recordings. See the image below.
When the usual relative durations of repolarization are not altered, the T wave remains upright, causing a saddleback ECG pattern (type 2 or 3). When the alteration in repolarization is sufficient to cause a reversal of the normal gradient of repolarization, the T wave inverts, and the coved (type 1) ECG pattern is seen. In a similar way, a heterogeneous alteration in cardiac repolarization may predispose to the development of reentrant arrhythmias, termed phase 2 reentry, which can clinically cause ventricular tachycardia and ventricular fibrillation.
An alternative hypothesis, the depolarization/conduction disorder model, proposes that the typical Brugada ECG findings can be explained by slow conduction and activation delays in the right ventricle (in particular in the right ventricular outflow tract).
One study used ajmaline provocation to elicit a type 1 Brugada ECG pattern in 91 patients, and found that the repolarization abnormalities were concordant with the depolarization abnormalities and appeared to be secondary to the depolarization changes. Using vectorcardiograms and body surface potential maps, investigators were able to show that depolarization abnormalities and conduction delay mapped to the right ventricle.
Symptoms
Many people don’t know that they have Brugada syndrome. This is because the condition either doesn’t cause noticeable symptoms or causes symptoms that are similar to other arrhythmias.
Some signs that you may have Brugada syndrome include:
- Feeling dizzy
- Experiencing heart palpitations
- Having an irregular heartbeat
- Gasping for breath or having difficulty breathing, particularly at night
- Seizures
- Fainting
- Sudden cardiac arrest
Symptoms can also be brought on by a variety of factors, including:
- Having a fever
- Being dehydrated
- Electrolyte imbalance
- Certain medications
- Cocaine use
What are complications of Brugada Syndrome?
If Brugada syndrome is untreated, the irregular heartbeats can cause fainting (syncope), seizures, and difficulty breathing, often when an affected person is resting or asleep. Sudden death is the most serious complication of Brugada syndrome. It usually happens unexpectedly, while a person is sleeping.
Complications of the use of an implantable cardiac defibrillator (ICD) may include:
- Unnecessary shocks
- Infection
- Bleeding
Diagnosis of Brugada Syndrome
If your doctor thinks you might have Brugada syndrome, they’ll recommend a physical exam along with some other tests:
Electrocardiogram (EKG or ECG)
This test records the electrical activity of your heart to find out if there’s a problem with its rhythm. A technician will put electrodes (small patches with wires) on your chest that pick up and record electrical signals from your heart. You also might take medication — usually given through an IV — that will help identify a certain pattern caused by Brugada syndrome.
Electrophysiology studies (EPS)
If an EKG shows you have Brugada syndrome, this test can help your doctor see where the arrhythmia is coming from and understand how to treat it. You’ll be given some medication to make you sleepy. Then they’ll put a flexible tube (called a catheter) through a vein in your groin and up to your heart. Electric signals are sent through the catheter, and they record what’s happening in the different areas.
Genetic testing
Genetic testing can help to confirm the diagnosis of Brugada syndrome, but is usually not helpful in estimating a patient’s risk of sudden death. Furthermore, genetic testing in Brugada syndrome is quite complex, and often does not yield clear-cut answers. Still, it can be useful to help identify affected family members.
Treatments for Brugada Syndrome
There’s currently no cure for Brugada syndrome, but there are things you can do to reduce your risk of experiencing serious problems.
If your doctor thinks your risk of developing a dangerously fast heartbeat is low, you might not need any treatment at first.
Avoid triggers
You can reduce your risk of developing a fast heartbeat by avoiding things that can trigger it, including:
- A high temperature – if you develop a high temperature, take painkillers such as paracetamol to bring it down; get medical advice as soon as possible if this does not help
- Drinking too much alcohol – avoid drinking lots of alcohol in a short space of time
- Dehydration – get medical advice if you have diarrhoea or you keep being sick, as you may lose a lot of fluid and may need to take special rehydration drinks
- Certain medicines – make sure any healthcare professional you see knows you have Brugada syndrome, and avoid medicines that can trigger the condition unless they’re recommended by a doctor – the BrugadaDrugs.org website has more information about medicines that could act as possible triggers
Implanted defibrillator
If there’s a high risk you could develop a dangerously fast heartbeat, your specialist may recommend having an implantable cardiac defibrillator (ICD) fitted.
An ICD is a small device placed in the chest, similar to a pacemaker. If it senses your heart is beating at a dangerous speed, it sends out an electric shock to help it return to normal.
An ICD does not prevent a fast heartbeat, but can help stop it becoming life threatening.
Antiarrhythmic drugs
Antiarrhythmic drugs such as Isoproterenol which are used during ventricular arrhythmias and electrical storms.
How do you prevent Brugada Syndrome?
Many cases of Brugada syndrome are related to a genetic defect. It’s not possible for you to prevent inheriting this condition. However, identifying the condition is key to preventing its potential complications. If you have Brugada syndrome and plan to have children, you may want to consult with a genetic counselor first.