Brugada Syndrome
An inherited heart rhythm disorder causing abnormal ECG patterns and a high risk of sudden cardiac death, often during sleep.
Emergency Management: Ventricular Fibrillation cardiac arrest. Requires immediate CPR and advanced cardiovascular life support (ACLS) with early defibrillation at 200J biphasic.
Brugada syndrome is a rare, inherited cardiac channelopathy characterized by typical electrocardiographic (ECG) alterations in the right precordial leads (V1-V3) and an increased risk of malignant ventricular tachyarrhythmias, syncope, and sudden cardiac death (SCD) in structurally normal hearts. It primarily affects the sodium channels of the heart.
Detailed Overview
First described in 1992 by the Brugada brothers, this syndrome accounts for up to 20% of sudden deaths in patients without structural heart disease. The hallmark is the Type 1 Brugada ECG pattern: a coved ST-segment elevation ≥2 mm followed by a negative T wave in ≥1 right precordial lead. Episodes of ventricular fibrillation (VF) typically occur during sleep or rest, often triggered by fever, vagal tone, or sodium channel blocking drugs.
Epidemiology & Demographics
Prevalence is estimated at 5 to 50 per 10,000 in endemic regions (Southeast Asia). It is much more common in males (8:1 ratio compared to females). The mean age of sudden cardiac death is around 40 years, though it can occur in childhood.
Etiological Mechanism
Autosomal dominant inheritance with incomplete penetrance. The most common mutation is in the SCN5A gene (accounting for ~20-30% of cases), which encodes the alpha subunit of the cardiac sodium channel (Nav1.5), leading to loss of function. Other minor gene mutations involve calcium or potassium channels.
Primary Causes
["Genetic mutations (primarily SCN5A loss of function)", "Precipitating triggers causing the phenotype to manifest (fever, extreme heat)", "Medications (Class IC antiarrhythmics like Flecainide or Propafenone, tricyclic antidepressants, cocaine)"]
The loss of function in the cardiac sodium channel (Nav1.5) decreases the inward sodium current (INa) during phase 0 of the action potential. This primarily affects the right ventricular epicardium, creating a prominent transient outward potassium current (Ito). This leads to heterogeneous repolarization between the epicardium and endocardium, setting the stage for phase 2 reentry and polymorphic ventricular tachycardia or ventricular fibrillation.
Diagnostic Criteria & Guidelines
Diagnosis requires a Type 1 Brugada ECG pattern (spontaneous or induced by a sodium-channel blocker test like Ajmaline or Flecainide) in ≥1 right precordial lead (V1, V2) positioned in the 2nd, 3rd, or 4th intercostal space. Must rule out structural heart disease.
Implantable Cardioverter-Defibrillator (ICD). It is the only proven therapy to prevent sudden cardiac death. Indicated (Class I) in patients who have survived a cardiac arrest or have documented sustained VT. Class IIa indication for patients with a spontaneous Type 1 ECG and history of syncope.
Second-Line & Adjunctive Therapy
Quinidine. Acts by blocking the transient outward potassium current (Ito). Used (e.g., Quinidine sulfate 300-600 mg every 6-8 hours) in patients with frequent ICD shocks (electrical storm) or in patients who refuse or cannot have an ICD.
Surgical & Procedural Management
Epicardial radiofrequency catheter ablation over the anterior right ventricular outflow tract (RVOT) is an emerging therapy for patients with recurrent VT/VF or frequent ICD shocks.
Patient Counseling & Advice
First-degree relatives must undergo clinical screening (ECG) and potentially provocative drug testing. Inform patients that the risk of sudden death is highest during sleep, hence the historical name 'Sudden Unexplained Nocturnal Death Syndrome'.
Follow-Up & Monitoring Schedule
Annual evaluation with a cardiologist/electrophysiologist. ICD interrogations every 3-6 months. Prompt ECG and evaluation if a fever occurs.
Preventive Strategies
Cannot prevent the genetic mutation. Prevention of arrhythmias involves fever suppression and avoidance of contraindicated medications.
Untreated, patients who have suffered a prior arrest or syncope have a very high recurrence rate of VT/VF (up to 30% over 3 years). With an ICD, mortality from arrhythmias is nearly eliminated.