Patients with Brugada syndrome may be asymptomatic for a long time and then suddenly develop syncope or ventricular fibrillation. You can find out how to recognize the rare genetic disease here.
In 1992, the brothers Josep and Pedro Brugada described arrhythmias that appear to emanate from a healthy heart and beyond Syncope can lead to death. Today we know that this rare disease has various genetic causes. 5 out of 10,000 people are affected by this rare arrhythmia – and every 5th sudden cardiac death has genetic causes, according to the result of a Study by Guo et al. A reason to carry out a “genetic autopsy” more often. That was also included in the study Brugada Syndrome (BrS) identified as one of the causes of death.
Brugada syndrome is a hereditary one Arrhythmiathe patients predisposed to ventricular arrhythmias and sudden cardiac death to develop.
Genetic cause deciphered
Brugada syndrome is classically one Kanalopathieie defective ion channels lead to mismanagement of nerve and muscle cells. Migraine and epilepsy are also canalopathies. 1996 shaped Japanese researchers the term Brugada syndrome (BrS).
Two years later, the first genetic change that caused this condition was found in SCN5A reported according to an autosomal dominant inheritance pattern. This gene encodes the α-subunit of cardiac sodium channel protein (Nav1.5), which is responsible for the initial rise in action potential. Other ion channels are also believed to be involved in the disease. Potassium, chloride and calcium ion channels involved in the cardiac depolarization and repolarization process, are associated with canalopathies and caused by the dysfunction of regulatory proteins. For example, excessive potassium efflux during early repolarization or reduced inward flow via calcium channels may contribute to Brugada syndrome pathophysiology.
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course and diagnosis
A recent one Study identified autoantibodies in the myocardium of affected patients against cardiac proteins (α-actin, skeletal α-actin, connexin-43, keratin) and observed abnormal expression of Nav1.5 α-subunit proteins. Although 23 genes have been linked to the condition, only SCN5Awhich encodes the cardiac sodium channel, causing disease.
Many Brugada diseases are asymptomatic, but the following symptoms can also occur:
- Syncope
- Ventricular tachycardia
- ventricular fibrillation
- cardiac arrest
- Sudden cardiac death
ventricular fibrillation typically occurs in patients at night or during periods of rest during increased vagal tone. In order to make the diagnosis of Brugada syndrome (BrS), a type 1 ECG with an upward convex is theoretically sufficient ST segment elevation by more than 2 mm in at least one right precordial lead at rest. However, the ST morphologies of Brugada patients show variations from day to day. Therefore, diagnosis with a 12-lead ECG remains a challenge, as the true prevalence of the syndrome in the general population is difficult to estimate.
BrS usually occurs in the third or fourth decade of life and about 63% of patients are asymptomatic at diagnosis.
ECG changes as the first clue
For diagnosis, the AHA consensus conference uses a classic shoulder type 1 ECG (“coved type”) in at least two leads (V1–3) and a clinical criterion required:
- Documented cardiac arrhythmia: polymorphic VT or VF
- Arrhythmia-related symptom: syncope, seizure, or nocturnal agonal breathing
- Positive family history: sudden cardiac death before the age of 45 or type 1 ECG in relatives
However, syncope or major arrhythmic events can occur at any age. Brugada syndrome is also associated with the sudden infant death (SIDS) connected. In 2017, the Report of the J-Wave Syndrome Consensus Conference found male dominance in Brugada syndrome, possibly due to testosterone modulation of ionic currents.
Ajmaline as a diagnostic tool
If the resting ECG is suspicious but not conclusive, a Ajmalin-Test to be carried out. The drug is injected intravenously into the patient with continuous ECG monitoring. The aim is to recognize the extent to which a type 1 BRU-ECG develops – which would be diagnostically conclusive. If the test is negative, a BrS unlikely.
Corona infection as a risk
For patients with BrS who develop COVID-19, the inflammatory response puts them at risk to cause ventricular arrhythmias. Also hypothermia can trigger for emergencies related to Brugada syndrome.
Exotic causes as triggers
Although Brugada syndrome is genetically terminated, it can be transmitted, for example through transplantation. Power et al. report on an “acquired” Brugada syndrome, in which a child received the heart from a previously unknown patient affected by the genetic defect. Post-transplant electrocardiographic monitoring of the recipient revealed persistent right bundle branch block and progressive, asymptomatic sinus node dysfunction.
A casuistry reported on an emergency that arose in the USA after the use of an electric weapon (teaser). The initial ECG showed ST segment and T wave changes in the precordial leads, similar to those found in Brugada syndrome.
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An up-to-date list of contraindicated drugs and further information on what to do in the event of fever, anesthetics and arrhythmia emergencies can be found on the homepage brugadadrugs.org
Therapy is mostly invasive
According to ESC guidelines, placement of an implantable cardioverter defibrillator (ICD) is recommended for the treatment of BrS patients recommended. Implantable cardioverter defibrillator implantation is an effective therapy for the prevention of arrhythmias in BrS patients. “However, it is also associated with complications, which is why the routine prophylactic use of ICDs in all BrS patients is not currently recommended,” said one Study von Lee et al.
A relatively new and promising approach to treating BrS patients is catheter ablation. Epicardial catheter ablation of the RVOT (right ventricular outflow tract) can be performed in patients with repeated appropriate ICD shocks be considered.
A pharmacotherapy with Chinidin or Isoproterenol should be considered in BrS patients for the treatment of recurrent arrhythmias such as VT/VF. quinidine can also be an alternative treatment option for supraventricular arrhythmias or in patients with contraindications for ICD placement. antiarrhythmics like Amiodarone or beta-blockers are not effective in preventing sudden death in symptomatic or asymptomatic patients with Brugada syndrome.
Offers a ray of hope for the future a gene therapywhich recodes defective gene sequences and restores the function of the defective ion channel.
Image source: Rene Böhmer, unsplash