Approach Considerations
Many patients with Brugada syndrome are young and otherwise healthy and may present with syncope. Patients with syncope should not be assumed to have a benign condition, and a 12-lead ECG should be performed.
A drug challenge with a sodium channel blocker should be considered in patients with syncope in whom no obvious cause is found. An experienced physician should interpret the ECGs, and an electrophysiologist should review them if possible.
Further testing may be indicated to exclude other diagnostic possibilities.
Laboratory Studies
Check serum potassium and calcium levels in patients presenting with ST-segment elevation in the right precordial leads. Both hypercalcemia and hyperkalemia may generate an ECG pattern similar to that of Brugada syndrome.
Laboratory markers, such as creatine kinase-MB (CK-MB) and troponin, should be checked in patients who have symptoms compatible with an acute coronary syndrome. Elevations indicate cardiac injury.
Genetic Testing
Patients with high likelihood of Brugada syndrome may be genetically tested for a mutation in SCN5A, which codes for the alpha subunit Nav 1.5 of the cardiac sodium channel. The results of this test support the clinical diagnosis and are important for the early identification of family members at potential risk. However, the yield of genetic testing remains relatively low at this time, with mutations in SCN5A found in only 11-28% of index cases. [20]
Echocardiography and MRI
Echocardiography and/or MRI should be performed, mainly to exclude arrhythmogenic right ventricular cardiomyopathy. However, these studies are also used to assess for other potential causes of arrhythmias, such as hypertrophic cardiomyopathy, unsuspected myocardial injury, myocarditis, or aberrant coronary origins.
Electrocardiography
Three ECG patterns have been described in Brugada syndrome [29] (see the image and table below). Placing the right precordial leads in the second intercostal space has been proposed to add sensitivity to the ECG diagnosis of Brugada syndrome. [30] Exercise stress testing may suppress ECG changes and arrhythmias.
Three types of ST-segment elevation in Brugada syndrome, as shown in the precordial leads on ECG in the same patient at different times. Left panel shows a type 1 ECG pattern with pronounced elevation of the J point (arrow), a coved-type ST segment, and an inverted T wave in V1 and V2. The middle panel illustrates a type 2 pattern with a saddleback ST-segment elevated by >1 mm. The right panel shows a type 3 pattern in which the ST segment is elevated < 1 mm. According to a consensus report (Antzelevitch, 2005), the type 1 ECG pattern is diagnostic of Brugada syndrome. Modified from Wilde, 2002. Image courtesy of Richard Nunez, MD, and EMedHome.com (http://www.emedhome.com/).
Table. ECG Patterns in Brugada Syndrome (Open Table in a new window)
Characteristic |
Type 1 |
Type 2 |
Type 3 |
J wave amplitude |
≥2 mm |
≥2 mm |
≥2 mm |
T wave |
Negative |
Positive or biphasic |
Positive |
ST-T configuration |
Cove-type |
Saddleback |
Saddleback |
ST segment, terminal portion |
Gradually descending |
Elevated by ≥1 mm |
Elevated by < 1 mm |
Recently, the QRS duration on 12-lead ECG has been suggested as a risk marker for vulnerability to dangerous arrhythmias. [31, 32] Inferolateral repolarization abnormalities have also been proposed to be a marker of risk. [33, 34]
Asymptomatic patients with a type 1 ECG pattern on routine ECG represent a difficult case. According to the latest consensus guidelines, a clinical electrophysiologist should evaluate patients in this situation. [18] Patients should be risk-stratified using the techniques described below, and a decision on implantable cardioverter-defibrillator (ICD) implantation should be made accordingly.
Signal-averaged ECG
Arrhythmogenic right ventricular cardiomyopathy (ARVC) and Brugada syndrome may be difficult to differentiate in some cases. Late potentials on signal-averaged ECG may reveal the fibrofatty degeneration of the right ventricle seen in ARVC.
Challenge with sodium channel blockers
In some patients, the intravenous administration of drugs that block sodium channels may unmask or modify the ECG pattern, aiding in diagnosis and/or risk stratification in some individuals. Infuse flecainide 2 mg/kg (maximum 150 mg) over 10 minutes, procainamide 10 mg/kg over 10 minutes, ajmaline 1 mg/kg over 5 minutes, or pilsicainide 1 mg/kg over 10 minutes. This challenge should be performed with continuous cardiac monitoring and in a setting equipped for resuscitation.
In patients with a normal baseline ECG, the results are positive when the drug generates a J wave with an absolute amplitude of 2 mm or more in leads V1, V2, and/or V3 with or without an RBBB. Administration of the drug should be stopped when the result is positive, when ventricular arrhythmia occurs, or when QRS widening of greater than 30% is observed.
Isoproterenol and sodium lactate may be effective as antidotes if the sodium channel blocker induces an arrhythmia, and the isoproterenol response may also have diagnostic use.
This drug test should not be performed in patients with a type 1 ECG pattern (see Table above) because it adds no new information.
In patients with the type 2 or 3 patterns, the drug challenge is recommended to clarify the diagnosis. [18] The sensitivity and specificity of drug challenge testing is not yet confirmed. A 2012 study examining patients with type 2 or 3 patterns showed that a positive drug challenge in symptomatic patients was associated with adverse events. However, asymptomatic patients with a similar result had a low event rate. This study suggests that a drug challenge may aid in risk stratification for symptomatic patients with a nondiagnostic ECG, but may not be justified in asymptomatic patients. [35]
Electrophysiologic Study
Some investigators use an electrophysiologic study (EPS) to determine the inducibility of arrhythmias, in an effort to risk-stratify patients with Brugada syndrome. However, the predictive value of this approach is debated. In 2001, Brugada showed that inducibility may be a good predictor of outcome. [36] However, in 2002, Priori reported a poor predictive value of invasive testing. [37] A subsequent study by Gehi concluded that EPS was not of use in guiding the management of patients with Brugada syndrome. [38]
More recently, investigators independently examining a large series of patients from Europe and Japan have failed to find any predictive value for EPS. In the large registry of Brugada syndrome patients from Europe, only symptoms and a spontaneous type 1 Brugada ECG pattern, but not EPS, were predictive of arrhythmic events. [39] In the smaller Japanese registry, only family history of sudden cardiac death at younger than 45 years and inferolateral early repolarization pattern on ECG predicted cardiac events. [34]
A study by Priori et al enrolled 308 patients with no history of cardiac arrest and a spontaneous or drug-induced type I ECG pattern. [40] Seventy eight of the patients had an ICD implanted prophylactically. EPS with a consistent stimulation protocol was performed on all patients; at a mean follow-up of 34 months, no differences were found in the incidence of appropriate ICD shocks or cardiac arrest between patients who were inducible and patients who were noninducible. Significant predictors of arrhythmia in this study included syncope and a spontaneous type I ECG pattern, a ventricular effective refractory period of less than 200 ms on EPS, and a fragmented QRS in the anterior precordial ECG leads.
Investigators from the United Kingdom examined a group of probands who suffered sudden arrhythmic death believed to be due to Brugada syndrome. [41] A retrospective review of risk factors determined that these patients would not have been considered high risk, calling into question the sensitivity of current risk factors (eg, symptoms, type I ECG pattern). However, few ECGs were available for examination in the probands with sudden death.
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Schematics show the 3 types of action potentials in the right ventricle: endocardial (End), mid myocardial (M), and epicardial (Epi). A, Normal situation on V2 ECG generated by transmural voltage gradients during the depolarization and repolarization phases of the action potential. B-E, Different alterations of the epicardial action potential that produce the ECG changes observed in patients with Brugada syndrome. Adapted from Antzelevitch, 2005.
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Three types of ST-segment elevation in Brugada syndrome, as shown in the precordial leads on ECG in the same patient at different times. Left panel shows a type 1 ECG pattern with pronounced elevation of the J point (arrow), a coved-type ST segment, and an inverted T wave in V1 and V2. The middle panel illustrates a type 2 pattern with a saddleback ST-segment elevated by >1 mm. The right panel shows a type 3 pattern in which the ST segment is elevated < 1 mm. According to a consensus report (Antzelevitch, 2005), the type 1 ECG pattern is diagnostic of Brugada syndrome. Modified from Wilde, 2002. Image courtesy of Richard Nunez, MD, and EMedHome.com (http://www.emedhome.com/).
Tables
Characteristic |
Type 1 |
Type 2 |
Type 3 |
J wave amplitude |
≥2 mm |
≥2 mm |
≥2 mm |
T wave |
Negative |
Positive or biphasic |
Positive |
ST-T configuration |
Cove-type |
Saddleback |
Saddleback |
ST segment, terminal portion |
Gradually descending |
Elevated by ≥1 mm |
Elevated by < 1 mm |
