Brugada syndrome

Brugada syndrome is an ion channel disorder in which there is an electrical disturbance of heart function without recognizable structural heart disease. This genetic heart rhythm disorder is associated with a significantly increased risk of dangerous ventricular arrhythmia, which can lead to loss of consciousness and, in the worst case, sudden cardiac death. Symptoms usually appear in the third or fourth decade of life.

It is believed that up to 20% of all cases of sudden cardiac death are due to Brugada syndrome [1]. The electrocardiogram (ECG) in patients with Brugada syndrome is characterized by a right bundle branch block-like widened ventricular complex and ST segment depression in the right precordial leads (Brugada type 1 ECG); occasionally an ECG shows no abnormalities, but only after administration of ajmaline (ajmaline test) [1].

Clinical features

Paroxysmal ventricular tachycardias (especially torsades de pointes) are characteristic and can be accompanied by the following symptoms [2]:

Syncope
pectangular complaints
General malaise
Sweating

Due to complications, cardiac arrhythmias can degenerate into ventricular fibrillation and even cardiac arrest. The first symptom of Brugada syndrome may be symptoms of dizziness, syncope (brief loss of consciousness) or surviving sudden cardiac death [1].

Case study: Type 1 ECG without inducible arrhythmia
A 33-year-old man with no previous cardiac history presented to a cardiology outpatient clinic after an incidental ST elevation in V2 was detected on ECG [4]. His family history was negative for early atherosclerotic cardiovascular events or sudden cardiac death. Due to a suspected Brugada syndrome, a procainamide test was performed, which revealed ST changes in the anterolateral leads. Although the diagnosis of Brugada syndrome was confirmed, the absence of cardiac arrest, tachyarrhythmia or syncope in his medical history suggests that he does not require further investigation. This is based on stratification data showing that an inducible type 1 pattern without prior symptoms or inducible arrhythmia has an increased but overall low risk of developing a ventricular arrhythmia [5,6]. However, as he had a positive diagnosis, he was tested for genetic components of Brugada syndrome and was advised to avoid drugs that inhibit cardiac sodium channels (class I antiarrhythmics, tricyclic antidepressants and lithium) in the future, as this carries the risk of triggering an arrhythmia. Another consideration in patients with Brugada syndrome is the immediate treatment of fever with antipyretics to prevent cardiac arrhythmias [7].

Diagnostics

In known familial cases, diagnosis is based on family history and molecular genetic mutation detection, although the latter is only positive in around 20% of cases [2]. If symptoms are suspected, the diagnosis can be made on the basis of specific ECG changes. The resting ECG shows a complete or incomplete right bundle branch block and ST-segment elevation of the right precordial leads (V1-V3) with subsequent T-negativization [2]. In addition to this (diagnostic) type 1, there are also types 2 and 3, each of which is associated with saddle-shaped ST-T complexes. Since these ECG features can also occur in trained endurance athletes with left ventricular hypertrophy, types 2 and 3 are not considered diagnostic.

In the silent (masked) type of disease, a normal ECG pattern is seen, which changes accordingly (unmasked) with oral administration of class I antiarrhythmic drugs. Due to the high complication rate of provocation tests (e.g. ajmaline test), accompanying ECG monitoring with defibrillator readiness is required. A further diagnostic procedure is the electrophysiological examination to record the intracardiac ECG.

Management and treatment

The implantable cardioverter defibrillator (ICD) is the only therapeutic option with proven efficacy in the primary and secondary prevention of cardiac arrest [3]. Correct risk stratification is therefore an important management objective. Quinidine can be considered as adjuvant therapy for higher risk patients and may reduce the number of ICD shocks in patients at risk of recurrence. Recently, epicardial ablation of the right ventricular outflow tract has emerged as a therapeutic option for patients at higher risk. The use of beta-blockers in the presence of Brugada syndrome is contraindicated. Ventricular tachycardia in the context of Brugada syndrome typically occurs from a bradycardia. Beta-blockers reduce the heart rate and can trigger bradycardia. This can increase the risk of paroxysmal ventricular tachycardia.

Literature:

Brugada syndrome, www.hdz-nrw.de/kliniken-institute/zentrale-dienste/kardiogenetik/untersuchungen/herzrhythmusstoerungen/brugada-syndrom.html,(last accessed 12/01/2023)
Brugada syndrome, https://flexikon.doccheck.com/de/Brugada-Syndrom,(last accessed 12/01/2023)
Brugada syndrome, www.orpha.net,(last accessed 12/01/2023)
Blotner M, et al: Workup for Suspected Brugada Syndrome: Two Case Reports for the General Practitioner. Cureus 2022 Feb 5; 14(2): e21921.
Brugada J, Brugada R, Brugada P: Determinants of sudden cardiac death in individuals with the electrocardiographic pattern of Brugada syndrome and no previous cardiac arrest. Circulation 2003; 108: 3092-3096.
Benito B, et al: Brugada syndrome. Rev Esp Cardiol Engl Ed 2009; 62: 1297-1315.
Brugada J, et al: Present status of Brugada syndrome: JACC state-of-the-art review. J Am Coll Cardiol 2018; 72: 1046-1059.