What are the diagnostic criteria and symptoms to watch out for in patients with Brugada syndrome?

Brugada Syndrome: Diagnostic Criteria and Clinical Symptoms

Diagnostic ECG Criteria

The diagnosis of Brugada syndrome requires a Type 1 ECG pattern showing coved ST-segment elevation ≥2 mm in one or more right precordial leads (V1 and/or V2), positioned in the second, third, or fourth intercostal space, occurring either spontaneously or after sodium channel blocker challenge (ajmaline, flecainide, procainamide, or pilsicainide). 1

Key ECG Features to Identify

• Type 1 Pattern (Diagnostic): Coved rSr' morphology with ST-segment elevation ≥2 mm followed by a negative T-wave in V1-V3 2, 1
• Type 2 Pattern (Non-diagnostic): "Saddle-back" morphology with high takeoff ST-segment elevation ≥2 mm, remaining ≥1 mm above baseline, followed by positive or biphasic T-wave 2
• Type 3 Pattern (Non-diagnostic): Either coved or saddleback morphology with J-point elevation ≥2 mm but terminal ST-segment <1 mm 2

Critical Diagnostic Considerations

• High precordial lead placement (second or third intercostal space) significantly improves detection of Type 1 pattern when standard V1-V2 leads are non-diagnostic 1
• The ECG pattern is highly dynamic and transient, fluctuating between normal and abnormal over time, requiring serial ECGs for diagnosis 1
• Only Type 1 pattern is diagnostic; Types 2 and 3 require sodium channel blocker challenge to unmask Type 1 pattern 2

Clinical Symptoms and Warning Signs

Cardinal Symptoms to Monitor

Syncope is the most critical symptom, particularly when occurring:

• At rest or during sleep (enhanced vagal tone) 1
• Without clear precipitating factors 3
• In patients with spontaneous Type 1 ECG pattern (6-fold higher cardiac arrest risk) 1

Sudden cardiac death or aborted cardiac arrest from polymorphic ventricular tachycardia/ventricular fibrillation 3, 4

Additional Clinical Features

• Seizure-like episodes (actually arrhythmic events misdiagnosed as seizures) 1
• Unexplained nocturnal agonal respirations (arrhythmias during sleep) 1
• Palpitations preceding syncope 4
• Atrial fibrillation (occurs more frequently than in general population) 4

Critical Triggers and Precipitants

Immediate Triggers Requiring Aggressive Management

• Fever: Most critical trigger for ventricular fibrillation requiring early, aggressive antipyretic treatment 3, 1
• Vagotonic states: Rest, sleep, post-prandial state 1
• Electrolyte disturbances: Hyperkalemia, hypercalcemia 2

Medications to Avoid

• Sodium channel blockers (Class I antiarrhythmics) 3
• Psychotropic medications (tricyclic antidepressants, phenothiazines) 3
• Anesthetic agents 3
• Cocaine 3
• Excessive alcohol intake 3, 1

Risk Stratification Framework

Highest Risk (Annual Event Rate 13.5%)

• Cardiac arrest survivors 3
• Spontaneous Type 1 ECG + syncope (presumed ventricular arrhythmia) 3
• Spontaneous Type 1 ECG + ≥2 risk factors (syncope, family history of sudden death <50 years, positive electrophysiologic study) 5

Intermediate Risk (Annual Event Rate 3.2%)

• Syncope with spontaneous Type 1 ECG 3, 1

Lower Risk (Annual Event Rate 1%)

• Asymptomatic with spontaneous Type 1 ECG 3
• Drug-induced Type 1 pattern only (very low risk, no chronic therapy needed) 1

Additional ECG Risk Markers

Beyond the Type 1 pattern, the following ECG features indicate increased arrhythmic risk:

• First-degree AV block (PR interval >200 ms) 4, 6
• QRS duration ≥120 ms in V2 4, 6
• Fragmented QRS complex 4, 6
• S wave in lead I (≥40 ms duration, amplitude ≥0.1 mV, area ≥1 mm²) 6
• R wave in lead aVR 6
• Inferior/lateral early repolarization pattern 4, 6
• T-wave alternans (sign of acute electrical instability) 4, 6

Family History Red Flags

• Sudden cardiac death in family members <50 years of age 1
• Unexplained drowning in young family members 1
• Type 1 ECG pattern in family members 1

Practical Clinical Approach

1. Confirm Type 1 pattern: Verify correct lead placement, repeat ECG, perform high precordial leads (V1-V2 in 2nd/3rd intercostal space) 1
2. Obtain detailed history: Personal syncope/seizures, family history of sudden death <50 years, unexplained drowning, exertional syncope 1
3. Refer to electrophysiologist regardless of symptoms when Type 1 pattern is confirmed 1
4. Consider sodium channel blocker challenge in patients with suspected Brugada syndrome but no baseline Type 1 pattern 1
5. Educate patients about arrhythmia triggers, forbidden drugs, and need for aggressive fever treatment 3, 1
6. Screen first-degree relatives with ECG and consider genetic counseling 3, 1

Common Pitfalls

• Missing the diagnosis due to transient ECG changes—serial ECGs are essential 1
• Misdiagnosing as right bundle branch block or early repolarization—use Corrado index and high precordial leads 1
• Underestimating fever risk—fever is a critical trigger requiring immediate aggressive antipyretic treatment 3
• Relying solely on genetic testing—SCN5A mutations account for only 20-30% of cases; diagnosis is primarily clinical and electrocardiographic 3, 1