Stanford Center for Inherited Cardiovascular Disease

The Brugada Syndrome In Depth

Background

Brugada Syndrome was first described in 1992 in a series of patients with sudden death who had similar, peculiar electrocardiogram (ECG) abnormalities. It was later found that many of these patients had abnormal function of their sodium ion channels. Patients with Brugada Syndrome develop ventricular tachycardia, a condition where the heart beats too quickly to maintain normal blood flow. Brugada Syndrome is rare. Although the number of patients with the condition is difficult to measure, approximately 4 out of 1,000 people in the United States have ECG findings of Brugada Syndrome. The condition is found more commonly in men and although more common in those of Asian descent, those of European background can also be affected. The average age at diagnosis is 42, but the condition can present itself at any age.

Diagnosis

The diagnosis of Brugada Syndrome can be difficult to make. Most patients do not suffer any symptoms until their first episode of ventricular tachycardia, which can cause dizziness, syncope (passing out) or even death. These episodes typically occur during sleep. The correct diagnosis hinges on the presence of the characteristic ECG findings in someone who had syncope or near sudden death. The ECG findings alone, without syncope, are not sufficient to make the diagnosis of “Brugada Syndrome”. Those who have ECG findings suspicious for the diagnosis, but who have not had syncope, are said to have a “Brugada Pattern”, and are treated differently.

The classic ECG findings of a classic “Type I Brugada Pattern” consists of a right bundle branch block with down-sloping ST segment elevations greater than 2mm and inverted T waves in leads V1 through V3. Type 2 and 3 Brugada Patterns also have a right bundle branch block-like pattern, but the ST segment has a saddleback appearance and T wave inversion is not as marked.

There is currently no “cure” for Brugada Syndrome and no medications that eliminate the risk of sudden death. However placement of an implantable cardiac defibrillator nearly eliminates the risk of dying suddenly from ventricular tachycardia. There are recommendations against competitive sports and potential complications from defibrillators. However, patients with a diagnosis of Brugada Syndrome who have defibrillators can essentially lead normal, productive lives.

Drug Challenge

One of the challenges of Brugada Syndrome is that ECGs findings are equivocal or the pattern can come and go. A Type 2 or 3 Brugada Pattern, even in the setting of symptoms, is not sufficient to make the diagnosis. If a patient has a Type 2 or 3 Brugada Pattern, several maneuvers, such as moving the ECG leads higher in the chest, can change the ECG to a classic Type 1 pattern. However, many times it is necessary to give these patients intravenous sodium channel blockers too turn the ECG into a more classic Type 1 pattern. The medications that are often used in the United States are flecainide or procainamide. This must be done in a controlled, monitored setting because ventricular tachycardia can occur during the drug challenge. In our institution, the drug challenge is performed in our electrophysiology laboratory and typically lasts less than one hour. Most patients with negative results go home the same day.

Electrophysiology Testing

Electrophysiology Testing (EP Study) is the process of stimulating the heart with small electrical impulses and recording electrical activity inside the heart. To do this, patients are brought to the electrophysiology laboratory, and thin catheters are placed through the leg veins, inside the heart. The catheters have electrodes at the tip and, like a pacemaker, this allows small impulses to be given inside the heart. This study typically lasts one to two hours and, if negative, is usually a same-day procedure.

Patients who have ECG findings that are characteristic of the Brugada Pattern, but who have equivocal symptoms or who have never had symptoms of syncope or near-sudden death, may have an unclear diagnosis. Electrophysiology testing can be used in this situation to identify patients at greater risk of dying suddenly and who may benefit from placement of a defibrillator. The study is not perfect, and whether or not it is performed will depend on the clinical situation. Patients are typically thoroughly evaluated, and this study is performed when the risk of sudden death remains unclear.

Genetics of Brugada Syndrome

Brugada Syndrome is typically caused by mutations in the sodium ion channel SCN5A or in genes that regulate the activity of the ion channel. These mutations are autosomal dominant, meaning that only one copy of the mutation is necessary to cause the disease. Although there are commercially available genetic tests, these tests only identify approximately 15-30% of the mutations that cause Brugada Syndrome, so a genetic test that is “negative” does not exclude the disease. In addition, there are patients with genetic mutations in SCN5A who never develop the disease, meaning that a “positive” test, in the absence of ECG findings and symptoms, does not mean that a person will develop the disease.

Genetic testing is most useful when one member of a family has been clinically diagnosed with Brugada Syndrome. If the mutation causing the disease in that person is identified, then the family members can be tested for the disease with genetic screening. We recommend genetic counseling before genetic tests are ordered to discuss the implications of the testing itself and the potential results.

Type 1.

Type 2.

Type 3.

Brugada 1

Brugada 2

Brugada 3

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