(See also Overview of Arrhythmias Overview of Arrhythmias The normal heart beats in a regular, coordinated way because electrical impulses generated and spread by myocytes with unique electrical properties trigger a sequence of organized myocardial... read more and Overview of Channelopathies Overview of Channelopathies Channelopathies are a group of genetic, autoimmune, or inflammatory conditions that alter cardiomyocyte ion channel function in a manner that predisposes to bradyarrhythmias or tachyarrhythmias... read more .)
The incidence of Brugada syndrome is approximately 1 in 1000 and is higher in people with Asian ancestry. The majority of patients with clinically apparent Brugada syndrome are male.
There are 3 patterns of Brugada syndrome, classified based on ECG parameters.
Pathophysiology of Brugada Syndrome
Brugada syndrome results from mutations that
Decrease inward sodium or calcium currents OR
Increase early outward potassium currents
These abnormalities lead to early loss of the action potential plateau, particularly in the epicardial cells of the right ventricular outflow tract that produce characteristic right precordial ECG changes and a propensity to ventricular tachyarrhythmias. Although different mutations have been reported, most are in SCN5A gene, producing a loss-of-function of the inward sodium current.
Typically, patients have no structural heart disease. Nevertheless, relationships with other genetic and acquired structural heart diseases are increasingly being recognized, as are overlap syndromes with long QT syndrome type 3 Long QT Interval Syndromes The long QT interval syndromes (LQTS) result from any congenital or acquired disorder of cardiac ion channel function or regulation (channelopathy) that prolongs ventricular myocyte action potential... read more and with arrhythmogenic right ventricular cardiomyopathy Arrhythmogenic Right Ventricular Cardiomyopathy Arrhythmogenic right ventricular cardiomyopathy (ARVC), also called arrhythmogenic right ventricular dysplasia (ARVD), is a genetic cardiac disorder affecting mainly the right ventricle and... read more (ARVC).
Symptoms and Signs of Brugada Syndrome
In some patients, Brugada syndrome has no clinical expression. However, in many patients it leads to syncope or sudden cardiac death due to polymorphic ventricular tachycardia Ventricular Tachycardia (VT) Ventricular tachycardia is ≥ 3 consecutive ventricular beats at a rate ≥ 120 beats/minute. Symptoms depend on duration and vary from none to palpitations to hemodynamic collapse and death. Diagnosis... read more and ventricular fibrillation Ventricular Fibrillation (VF) Ventricular fibrillation causes uncoordinated quivering of the ventricle with no useful contractions. It causes immediate syncope and death within minutes. Treatment is with cardiopulmonary... read more . About 10% of patients develop atrial tachyarrhythmias, predominantly atrial fibrillation Atrial Fibrillation Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form... read more .
Events occur more often at night and are not usually related to exercise. Events may also be brought on by fever and by certain drugs, including sodium channel blockers, beta-blockers, certain antidepressants and antipsychotics, lithium, alcohol, and cocaine.
Diagnosis of Brugada Syndrome
Provocative testing to induce characteristic ECG changes
Diagnosis should be considered in patients with unexplained cardiac arrest or syncope or a family history of such when the affected people do not have structural heart disease.
Initial diagnosis of Brugada syndrome is based on a characteristic ECG pattern, the type 1 Brugada ECG pattern (see figure Type 1 Brugada ECG pattern Type 1 Brugada ECG pattern ). The type 1 Brugada ECG pattern has prominent ST elevation in V1 and V2 (sometimes involving V3) that causes the QRS complex in these leads to resemble right bundle branch block Bundle Branch Block and Fascicular Block . The ST segment is coved and descends to an inverted T-wave.
Lesser degrees of these patterns (type 2 and type 3 Brugada ECG patterns) are not considered diagnostic. The type 2 and type 3 patterns may change to a type 1 pattern spontaneously, with fever, or in response to drugs. The latter is the basis of a challenge diagnostic test usually using IV ajmaline, procainamide, flecainide or pilsicainide.
The role of electrophysiologic testing is currently debated. Genetic testing is usually recommended but has a yield of approximately 20% to 30%.
Type 1 Brugada ECG pattern
Prominent J-point elevation to a coved ST segment, leading to an inverted T-wave in leads V1 and V2.
Treatment of Brugada Syndrome
Screening of family members
Patients with a spontaneous or provoked Type 1 Brugada syndrome ECG pattern and recent unexplained syncope, sustained VT, or cardiac arrest should typically have an implantable cardioverter-defibrillator Implantable Cardioverter-Defibrillators (ICD) The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more (ICD).
When frequent ICD discharges need to be suppressed, quinidine, which blocks the transient outward potassium current that may be increased in Brugada syndrome, may be efficacious. IV isoproterenol has also been used if the cause of the frequently recurrent arrhythmias appears transient and reversible.
Best treatment of Brugada syndrome in patients diagnosed based on ECG changes and family history but who do not have syncope or arrhythmia is unclear, although they do have increased risk of sudden death.
Prevention of Brugada Syndrome Arrhythmias
It is important to avoid factors that can trigger arrhythmias. Patients should monitor their temperature during infectious illness and take antipyretic therapy for fever. When possible, clinicians should stop any predisposing drugs and prescribe alternatives. Patients should avoid substances, particularly cocaine and excessive alcohol, that are arrhythmogenic in Brugada syndrome (for an up-to-date list, see www.brugadadrugs.org).
Brugada syndrome is a genetic disorder causing characteristic ECG changes and an increased risk of ventricular arrhythmias causing syncope and sometimes sudden cardiac death at a relatively young age
Risk factors for symptomatic arrhythmias include fever, and numerous drugs, including alcohol
Diagnosis is by ECG, sometimes with provocative testing
An implantable cardioverter-defibrillator may be required
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
www.brugadadrugs.org: Aims to provide up-to-date information on safe drug use in Brugada syndrome
Drugs Mentioned In This Article
|Eskalith, Eskalith CR, Lithobid
|Procanbid, Pronestyl, Pronestyl-SR