History and exam
Key diagnostic factors
common
past history of unexplained cardiac arrest or documented PMVT or VF
Consider a diagnosis of symptomatic Brugada syndrome (BrS) if a patient has a past history of unexplained cardiac arrest, or documented polymorphic ventricular tachycardia (PMVT), or ventricular fibrillation (VF).[1][5][7]
There are many causes of sudden cardiac arrest, PMVT and VF, but BrS should be considered as a differential, particularly if there is Brugada pattern on ECG and one or more risk factors for BrS.
Patients may also present with monomorphic VT, but this is rare and should prompt investigation of other arrhythmogenic cardiomyopathies.[5][52][53]
cardiogenic syncope
Consider a diagnosis of symptomatic Brugada syndrome (BrS) if a patient presents with, or has a past history of cardiogenic syncope.
Up to one third of patients with BrS present with, or have a history of, syncope at the time of diagnosis.[54]
Take a careful history to differentiate cardiogenic from noncardiogenic causes of syncope.[1][7] The published Shanghai score for BrS assigns two points to patients with suspected cardiogenic syncope, and one point to those with an unclear cause of syncope (see Criteria).[1][49]
Patients with BrS who have a history of cardiogenic syncope are also at 2.5 to 5-fold greater risk of serious arrhythmic events compared with those with noncardiogenic syncope.[48][47][56][57] Patients with cardiogenic syncope have not been shown to have an increased risk for serious arrhythmic events.[58]
Other diagnostic factors
common
inducible features of Brugada syndrome
Features of Brugada syndrome (BrS) may only be apparent when induced by certain factors.[1][7] Inducible features are particularly important to identify in asymptomatic patients (i.e., those who do not have a past history of unexplained cardiac arrest, ventricular arrhythmias, or syncope), but may also be present in symptomatic patients. These include:[1][7]
Febrile illness. This is known to induce type 1 Brugada pattern on ECG and precipitate arrhythmic events.[1] In endemic regions, the prevalence of BrS in patients presenting with febrile illness for any reason has been reportedly as high as 4%, approximately 20-fold greater than a nonfebrile control group in one Thai cross-sectional study of 401 patients.[20][21] While in isolation fever is not specific for BrS, in a patient with suspected BrS, it has implications for both diagnosis and management.[1]
Medications. These include sodium-channel blockers (e.g., flecainide, procainamide), psychotropic medications (e.g., tricyclic or tetracyclic antidepressants, lithium), and local anesthetics. These are known to induce type 1 Brugada ECG changes and may also precipitate arrhythmic events.[1][18]
Illicit drugs or alcohol. These are known to induce type 1 Brugada ECG changes and may also precipitate arrhythmic events.[1][18]
uncommon
atrial arrhythmias
Consider a diagnosis of Brugada syndrome (BrS) in a patient <30 years who has atrial fibrillation or flutter.[1][59][60] Concomitant atrial arrhythmias are common in patients with BrS, with a prevalence of approximately 10%, although these are not specific for diagnosis of BrS.[61][64] Use of sodium-channel blockers may unmask Brugada pattern on ECG in some of these patients.[61]
nocturnal agonal respirations
Can be a feature of Brugada syndrome (BrS).[1][7]
The Shanghai score for BrS assigns 2 points to patients with nocturnal agonal respirations (see Criteria).[1][49]
In a Danish national survey, prevalence of nocturnal agonal respirations in patients with BrS was 14%, but this is likely to be greater in endemic areas.[61]
Nocturnal agonal respirations were described in early reports from Southeast Asia (Philippines, Thailand, Japan, China, and others) of sudden unexpected nocturnal death syndrome (SUNDS), a syndrome which is thought to be genetically, phenotypically, and functionally the same as BrS.[63]
Risk factors
weak
age 30 to 50 years
Brugada syndrome (BrS) is typically first diagnosed in young to middle-aged patients.[1]
Patients aged 30-50 years with BrS are also at high risk of serious arrhythmic events.[39] This is also typically the age at which patients with BrS may present with their first serious arrhythmic event.[1] However, serious arrhythmic events have also been reported in children as young as <1 year old.[21][40][41] Women in particular may be more likely to have their first SAE in childhood, or later in life.[1][39]
Patients >50 years who have BrS experience significantly fewer serious arrhythmic events compared with younger patients, and for those ≥55 years at the time of BrS diagnosis, annual mortality is similar to that of the general population.[41][42][43] However, it remains unclear whether these observations are due to protective effects acquired through aging or simply represent selection bias.
male sex
Brugada syndrome (BrS) is more common in men compared with women.[1][39] Men account for up to 90% of cases of BrS in some cohorts.[1][39]
Evidence has shown that men with BrS are also at increased risk of serious arrhythmic events.[44][45][46] However, this finding remains controversial, and has not been confirmed with complete adjustment for potential confounding factors.[47][48]
Asian ancestry
Brugada syndrome (BrS) occurs more commonly in Asia compared with Europe and the US.[1][13] BrS is particularly common in Southeast Asia, where a nocturnal sudden death syndrome in young men was clinically reported by a variety of local names in countries such as Philippines, Thailand, Japan, and China, prior to the formal classification of BrS.[14]
family history of BrS or suspicious or unexplained cardiac death
Determine the following features (which form part of the Shanghai score; see Criteria) in any first- or second- degree relative of the patient.[1][49]
Definite Brugada syndrome (BrS)
Suspicious sudden cardiac death (febrile, nocturnal, confounded by BrS-associated drug)
Unexplained sudden cardiac death <45 years with non-contributory autopsy.
Bear in mind that, although family history is a standard and important part of any diagnostic evaluation, limited evidence exists to support a family history of sudden cardiac death as a risk factor for BrS-associated arrhythmic events.[50]
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