Brugada Syndrome (Heart Rhythm Disorder)

Brugada Syndrome Definition

Brugada syndrome is  an inherited life-threatening condition where there is a disorder with the heart rhythm that leads to sudden death. The condition is characterized by a distinct abnormal heartbeat known as Brugada sign which can be detected on an electrocardiogram (ECG). Brugada syndrome may result in abnormal heartbeat, fainting, heart attack, and sudden death. Most people with Brugada syndrome do not show any symptoms. Therefore the condition is often missed. Brugada syndrome is inherited in an autosomal dominant manner, which means getting one defective gene from either parent can lead to the development of the condition.

Brugada Syndrome Incidence

In United States, Brugada syndrome affects 2 out of 1,350 people of white and Hispanic population. However, Brugada syndrome affects Asian and other ethnic populations more in the global context. Brugada syndrome affects men more frequently than women. Young males make up most cases of Brugada syndrome.

About Brugada Syndrome Video

Brugada Syndrome Pathophysiology

Heart beats result from contraction of the heart muscles. Electrical signals regulate these contractions. These electrical signals arise in the sinoatrial node (SA node) in the heart wall. It is also known as the natural pacemaker. The electrical signals are then passed to the heart muscles in a coordinated way that ensures that atria (chambers that receive blood) contract while the ventricles (chambers that push out blood) relax and vice versa. When the electrical signals from the nerves reach the heart muscle, it causes a flow of ions into and out of heart muscle cells. This flow of ions takes place through special channels called ion channels. This movement of ions results in muscle contraction.

Any problem in this whole process can lead to irregular heartbeat which is broadly known as an arrhythmia. One such disrupt known as  channelopathy arises when the function of the ion channels are disturbed. In channelopathies, there may be changes in the pattern of electrical activities that are responsible for rhythmic contractions. Brugada syndrome also is an example of a channelopathy, in which there are changes (mutations) in sodium or Na+ channel of the heart cells. These changes decrease the sodium current available during the heartbeat. In Brugada syndrome, these abnormalities in electrical activities have a specific pattern and are called Brugada signs.

Brugada Syndrome Symptoms

Many people with Brugada syndrome do not show any noticeable symptoms and the condition remains undiagnosed until there is a severe episode which can even be life threatening. When symptoms of Brugada syndrome are present, it is largely non-specific. This means that the symptoms of Brugada syndrome are largely similar to some other heart rhythm problems.

Brugada Sign

The key symptom specific to Brugada syndrome is Brugada sign. This abnormal pattern can only be detected on an ECG. However, an ECG is not routinely conducted on a person under 5 years of age and even older patients may not opt for screening unless advised by a physician.

Other Symptoms

Other symptoms of Brugada syndrome include the following:

  • Fainting
  • Palpitations
  • Irregular heartbeats
  • Sudden cardiac arrest
  • Family history of sudden heart failure
  • Heart failure mostly during rest or sleep

Triggers

There are often no clearly identifiable triggers for the onset of the symptoms. Physical activity can sometimes be a trigger but this is rare, unlike in other more cardiac conditions such as a myocardial infarction (heart attack). Fever often triggers the symptoms of Brugada syndrome. Other triggers may include :

  • Abnormally high or low blood sodium levels (hypernatremia or hyponatremia respectively)
  • High blood calcium levels (hyercalcemia)
  • Alcohol or cocaine intake
  • Use of certain medicines like sodium channel blockers, anti-depressants, vagotonic agents, beta-adrenergic blockers, alpha-adrenergic agonists, and a combination of insulin and glucose.

Brugada Syndrome Causes

The abnormal heartbeats in Brugada syndrome are caused by defects in ion channels within the heart muscle cells. Due to these defects, the contraction of heart muscle cannot occur in a coordinated manner. Therefore the heart is unable to pump blood effectively. As a result, there is less blood available to body organs including brain. This causes fainting or sudden heart failure.

In most of the cases, the channel disturbance in Brugada syndrome is inherited. The gene that is changed or mutated in Brugada syndrome is known as SCN5A gene. Changes in this gene result in abnormal functioning of sodium ion channels, which causes disordered heartbeat rhythms. However, Brugada syndrome can also result from subtle structural abnormalities in the heart, electrolyte imbalance, or from the use of certain chronic medicines or cocaine usage.

Brugada Syndrome Risk Factors

Risk factors for Brugada syndrome may include the following:

  • Family history of Brugada syndrome increases the risk of developing the condition.
  • Male gender is a known risk. Brugada syndrome is almost 10 times more common in men than in women.
  • Brugada syndrome affects Asians more frequently than other races.
  • Fever may increase the risk of fainting or other complications of Brugada syndrome.

Brugada Syndrome Complications

Complications associated with Brugada syndrome include the following:

  • Sudden heart attack, which can be fatal if occurs while sleeping.
  • Fainting, which increases the risk of falling and accidents.
  • Changes in neurological status due to reduced oxygen supply to brain.

Brugada Syndrome Diagnosis

Following tests can be performed to diagnose symptoms of Brugada syndrome:

  • A typical physical examination is usually performed to check the vital signs. Medical history is thoroughly assessed.
  • An electrocardiogram (ECG) can detect irregularities in heart’s rhythm and structure. For some patients including unconscious ones, ECG is sometime taken after administering a drug called sodium channel blocker (e.g., flecainide, procainamide, ajmaline, or pilsicainide) intravenously. This drug will change the heartbeat patterns and help in detecting abnormalities in heartbeat rhythm. If the use of a sodium channel blocker disrupts heartbeat further, substances called isoproterenol and sodium lactate are given as antidotes.
  • In an electrophysiology (EP) test, few electrodes passed through a catheter detect the electrical signals running through the heart.
  • Genetic testing is recommended if there is a family history of Brugada syndrome or sudden heart failure. Mutations in SCN5A are checked in a genetic test.
  • Echocardiography and magnetic resonance imaging (MRI) scan can detect injuries, inflammation, or other diseases of heart muscles.

Brugada Syndrome Treatment

Patients with a family history of sudden heart failure, a history of serious heart rhythm problems, and fainting spells are considered high risk cases.

Medical devices

Treatment of Brugada syndrome includes use of a medical device called an implantable cardioverter-defibrillator (ICD). Implantation of an ICD requires hospitalization for 1 to 2 days. ICD continuously monitors heart rhythm. In case of abnormal heartbeats, it delivers electrical shocks to control the situation. Though very effective in preventing sudden death from Brugada syndrome, ICDs may cause some life-threatening complications in patients (receiving shocks even upon regular heartbeat).

Medication

Though several drugs have been tried on patients with Brugada syndrome, the results have not been very encouraging. For this reason, medical practitioners recommend use of an ICD over medicines. A drug called quinidine can block a part of electric currents and maintain a normal heart rhythm. Thus, it normalizes the ECG pattern in patients. The side-effects arise due to its ability to block sodium currents. More drugs like tedisamil and isoproterenol can also be given.

Lifestyle measures

Physical activities may increase a phenomenon called vagal tone (body’s control to stop heartbeat). For this reason, patients with Brugada syndrome are advised to abstain from activities that require strenuous exercise.

References :

http://emedicine.medscape.com/article/163751-overview

http://www.mayoclinic.com/health/brugada-syndrome/DS01142/

http://familyheart.stanford.edu/clinics/brugada2.html

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