About 10–20% of patients dying suddenly or resuscitated from ventricular fibrillation do not have demonstrable heart disease. These people are often young and tragically in some cases sudden death is the first and only clinical event. One of the three main electrophysiological diagnoses to be considered in these situations is the Brugada syndrome. A case of Brugada syndrome is described, together with an example of the classic electrocardiographic manifestations and a discussion of the possible aetiology, diagnosis and management of this condition.
- Brugada syndrome
Statistics from Altmetric.com
At approximately 6 pm one evening, a 29 year old man presented at the accident and emergency (A&E) department in a critical condition. The history obtained from both the paramedics and police was unusual. The policeman had been driving his car on the motorway when the car in front, carrying a single occupant, suddenly veered off the road, crashed through a barrier and came to a stop in a field. The policeman found the driver to be in cardiorespiratory arrest, and started resuscitation at the scene. On arrival, the paramedics discovered the driver's initial cardiac rhythm to be ventricular fibrillation and he was successfully defibrillated. During transfer to the A&E department he required defibrillation for a further episode of ventricular fibrillation.
On arrival in hospital he was agitated, with a Glasgow Coma Score of 8/15 but was breathing spontaneously with a partially obstructed airway. The monitor showed normal sinus rhythm with an initial blood pressure of 130/80. He was given a rapid sequence induction of anaesthesia to maintain and protect his airway. Initial primary and secondary trauma surveys revealed no obvious injury and initial chest, pelvis, and c-spine radiographs were unremarkable. Initial speculative diagnoses included spontaneous intracerebral haemorrhage, cardiac arrhythmias and convulsion. The patient had urgent computed tomography of the head, which was normal. Further history from the family revealed no previous medical problems and no relevant drug history.
The initial 12 lead electrocardiograph (ECG) (see fig 1) showed a partial right bundle branch block with ST segment elevation in chest leads V1 to V3. At this stage a primary cardiac problem was thought to be more likely. Urgent echocardiography to look for structural cardiac disease was performed. No abnormality was found. Throughout this time period the patient maintained a normal sinus cardiac rhythm. He was transferred to an intensive care bed and weaned uneventfully from ventilation over a period of 24 hours. Toxicology screening was negative.
After extubation he was neurologically intact and was transferred to the care of the cardiologists for further investigation. Coronary angiography was carried out to exclude coronary artery disease and congenital artery anomalies. None were found. Right ventricular angiography showed no impairment of function. The clinical and electrocardiographic features confirmed the diagnosis of Brugada syndrome. An implantable defibrillator was inserted within days of presentation and the patient was discharged home.
Subsequent follow up has been unremarkable with no further episodes of arrhythmias.
About 10–20% of patients dying suddenly or resuscitated from ventricular fibrillation do not have demonstrable heart disease.1 Unexpected arrhythmogenic death occurring in people with minimal or no structural heart disease is estimated to represent 3% to 9% of out of hospital cases of ventricular fibrillation unrelated to myocardial infarction.2 These patients are often young and tragically sudden death may be the first and only clinical event.
When acute ischaemia is not the cause of sudden cardiac arrest, there are three main electrical cardiac disorders to be considered as the possible cause of ventricular fibrillation: the Brugada syndrome, the long QT syndrome, and the Wolff-Parkinson White syndrome. If these three disorders are excluded, and the heart is structurally normal, then ventricular fibrillation is considered idiopathic.
In 1992 Pedro and Josep Brugada3 described eight otherwise healthy patients with sudden and aborted cardiac death, in whom they found “right bundle branch block and persistent ST segment elevation in leads V1 to V3”. Based on these observations they outlined a new distinct clinical and electrocardiographic syndrome. This was subsequently called the Brugada syndrome. In these patients the ECG showed right bundle branch block, normal QT interval and persistent ST elevation in the precordial leads V1 to V2–V3 not explainable by electrolyte disturbances, ischaemia or structural heart disease. All these patients had right bundle branch block. Repolarisation was abnormal, characterised by persistent ST elevation (at least 0.1 mV) in leads V1 to V2–V3. The PR and QT intervals were within normal limits. ECG features of right bundle branch block with ST elevation in the right precordial leads has subsequently been described as the “Brugada sign”.4
ST segment elevation in the right chest leads is observed in a variety of clinical and experimental settings and is not unique or highly specific for the Brugada syndrome. A clear distinction of this syndrome cannot be made on the basis of the ECG alone. The prevalence of idiopathic ST segment elevation is reported to be 2.1% to 2.65%. An elevated ST segment limited to the right precordial leads occurs in less than 1% of all cases of elevated ST segment.2 However, ST segment elevation in the right precordial leads in the absence of ischaemia, electrolyte or metabolic disorders, pulmonary or inflammatory disorders or abnormalities of the central or peripheral nervous system is suggestive of the Brugada syndrome. In many cases of Brugada syndrome, the ECG manifestations can normalise transiently, leading to underdiagnosis of the syndrome.2 Strong sodium channel blocking agents such as procainamide and flecainide can unmask the ST segment elevation in many patients thus aiding diagnosis.
Brugada reported that malignant arrhythmias eventually occur in 27% of initially asymptomatic patients who have the Brugada sign. On the basis of reports published it has been speculated that 40% to 60% of patients diagnosed as having idiopathic ventricular fibrillation may actually suffer from Brugada syndrome.5 It is now thought to be the most frequent cause of sudden cardiac death in patients without structural heart disease under the age of 50 years.
Brugada syndrome is a cause of sudden cardiac death in previously healthy young people.
ECG characteristics include: ST elevation in pre-cordial leads (V1–V3), right ventricular conduction delay with a normal QT interval.
These patients require early cardiology opinion and electrophysiological investigation.
Treatment consists of implantable defibrillators to prevent sudden death from ventricular fibrillation.
The mean age of affected people is mid to late thirties. In the majority of cases tachyarrythmias occur at rest and in many cases during the night. The recurrence rate of new arrhythmic events is as high as 40% in these patients.5
Current available data suggest that the Brugada syndrome is a primary electrical disease resulting in abnormal electrophysiological activity in the right ventricular epicardium. Electrical heterogeneity within the right ventricular epicardium leads to the development of coupled premature ventricular contractions via a re-entrant mechanism that precipitates ventricular tachycardia/fibrillation (see fig 2). The role of right bundle branch block in Brugada syndrome has been a matter of controversy. Conduction delay in the right ventricle does not seem to be an integral part of the syndrome. Furthermore, there seems to be no correlation between right bundle branch block and cardiac death, whereas a definite link exists between the magnitude of ST elevation and the incidence of the life threatening arrythmias seen in these patients.2
The aetiology of Brugada syndrome is controversial. Brugada and Brugada suggested no structural abnormality of the heart, claiming the syndrome was attributable to the presence of a functional electrical disease.6 Martini et al suggested the presence of concealed right ventricular myocardial disease. Corrado et al report that a familial cardiomyopathy that mainly involves the right ventricle and conducting syndrome is responsible.7 An ion channel defect resulting in heterogeneous loss of the action potential dome in right ventricular epicardium has been proposed as a mechanism for Brugada syndrome. Three different mutations of the gene of the sodium channel SCN5A on chromosome three have been identified.8 The Brugada syndrome is autosomal dominantly inherited but has variable expression. Testing of all family members is important because of the high incidence of familial occurrence.
Patients with Brugada syndrome have a high incidence of sudden death, and prophylactic defibrillators are indicated in those with inducible arrhythmias at electrophysiological study, irrespective of symptoms.9 In contrast, the incidence of sudden death in the long QT syndrome is very low, making prophylactic defibrillator implantation not cost effective. Even with the best medical treatment, arrhythmia recurrence rates are still 45–50% at five years. Pharmacological treatment does not protect against recurrent events and implantation of an cardiac defibrillators is the only proven effective treatment in preventing sudden death in patients with the Brugada syndrome.10, 11 Emergency physicians therefore have an important role in referring suspected cases of Brugada syndrome for urgent cardiology opinion for consideration of an implantable defibrillator.
Conflicts of interest: none.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.