Brugada syndrome: the essentials

A free full text review was recently published on this topic. Some of the key questions addressed:

What is it?

Brugada syndrome is a genetically heterogeneous channelopathy, first described in 1992, capable of causing arrhythmia, syncope and sudden cardiac death.

What is the presenting arrhythmia?

PMVT or VF. Less commonly MMVT.

When should you suspect it?

In a patient with characteristic ECG findings inquire about syncope or a family history of syncope, drowning or SCD. In a patient with such a personal or family history look for characteristic ECG findings. Know the typical patterns (see below).

How do you make the definitive diagnosis?

Although features from the clinical history are said to strengthen the diagnosis the new (2013) criteria are purely electrocardiographic. From the article:

1.

BrS is diagnosed in patients with ST-segment elevation with type I morphology greater than or equal to 2 mm in greater than or equal to 1 lead among the right precordial leads V1,V2 positioned in the 2nd, 3rd, or 4th intercostal space occurring either spontaneously or after provocative drug test with intravenous administration of Class I antiarrhythmic drugs.

2.

BrS is diagnosed in patients with Type 2 or Type 3 ST-segment elevation in greater than or equal to1 lead among the right precordial leads V1,V2 positioned in the 2nd, 3rd, or 4th intercostal space when a provocative drug test with intravenous administration of Class I antiarrhythmic drugs induces a Type 1 ECG morphology.

Note that you explore along three intercostal spaces with the V1-2 electrodes in attempting to elicit the pattern. Also note that drug challenge is contraindicated in patients who spontaneously exhibit the type 1 pattern. This is because it is unnecessary according to present diagnostic criteria and may provoke arrhythmia.

What electrophysiologic mechanisms are at play?

Inhomogeneous sodium channel defects cause transmyocardial voltage gradients and inhomogeneous repolarization, leading to the arrhythmia substrate. Triggering PVCs are close coupled and arise from the RVOT and thus can be ablated as an option for patients who suffer from electrical storm.

What are the genetics of Brugada syndrome?

At least 16 genes have been identified but no known mutation is present in the majority of cases. Most of the mutations are novel, found in isolated individuals or families. It has been traditionally thought to be autosomal dominant but recent evidence indicates that the genetic picture is more complex and some cases may be polygenic.

What are the management recommendations?

For symptomatic Brugada syndrome patients (syncope, cardiac arrest) : ICD implantation.

For asymptomatic patients meeting electrocardiographic criteria: avoidance of contraindicated drugs (see this list) and management of aggravating conditions such as fever and hypokalemia.

Note: quinidine can reverse the Brugada pattern and reduce arrhythmias but is not generally recommended due to a lack of high level evidence that it improves clinical outcomes, proarrhythmic effects of its own and a lack of general availability.

Asymptomatic patients who exhibit the pattern only during certain acute illnesses or exposure to sodium channel blocking drugs are considered at very low risk.