3.Discussion
Brugada pattern describes asymptomatic patients with ECG finding of a
pseudo-right bundle branch block and persistent ST segment elevation in
leads V1 to V2 with no other clinical criteria. It can be discovered in
casual ECG or as part of the screening of first-degree relatives of a
Brugada proband. There are two main types of Brugada ECG patterns:
Type 1: the elevated ST segment ≥ 2mm descends with an upward
convexity to an inverted T wave. This is referred to as the “coved
type” Brugada pattern.
Type 2: the ST segment has a “saddle back” ST-T wave configuration,
in which the elevated ST segment descends toward the baseline, then
raises again to an upright or biphasic T wave.
In some patients, the characteristic ECG changes of the Brugada pattern
are transient or variable over time. Provoking factors are:
- Fever.
- Medications, (eg, class 1c antiarrhythmic agents, Beta blockers,
tricyclic or tetracyclic antidepressant) .
- metabolic disturbance (eg, severe hyperkalemia)
- toxins (eg, Alcohol and Cocaine)
Brugada syndrome is symptomatic Brugada pattern with one or more of
these clinical criteria:
- Sudden cardiac arrest (SCA) occurs in one-third of the patients due to
nonstructural ventricular tachyarrhythmia, most often presented as
ventricular fibrillation (VF) or polymorphic ventricular tachycardia.
SCA is usually not associated with exercise, and it’s more common at
night and during sleep.
- Episode of syncope due to tachyarrhythmia cause. However, syncope due
to non-arrhythmic causes (eg, neurocardiogenic) could happen with a
benign prognosis.
- Palpitation due to related atrial fibrillation occurs in 10 to 20
percent in patients with Brugada syndrome. The presence of AF is
associated with increased disease severity and higher risk of VF. On
the other hand, palpitations related to ventricular tachyarrhythmia
are not common.
- Nocturnal agonal respiration, that may represent aborted cardiac
arrhythmias and is considered an ominous symptom.
Arrhythmic events generally occur between the ages 22 and 65 years and
peak between 38 and 48 years. They are rare in children. However,
patients with ventricular premature beats or non-sustained ventricular
tachycardia are generally not considered as Brugada syndrome but Brugada
pattern.
Management of Brugada pattern patients:
- Additional tests to exclude underlying heart disease (eg, myocardial
ischemia).
- Risk evaluation: electrophysiology testing, signal-averaged ECG,
12-lead ECG and drug challenge in specific cases.
- Genetic testing (eg, SCN5A, SCN10a genes) for Brugada syndrome
probands.
- Implantable cardioverter-defibrillator (ICD) in case one of:
- Documented ventricular fibrillation.
- Polymorphic ventricular tachycardia.
- Unexplained syncope strongly suggestive of a tachyarrhythmia.
- Nocturnal agonal respiration in the setting of type 2 Brugada pattern.
Fever is a common source for Brugada pattern, a study assessed the
prevalence of Brugada pattern in consecutive patients with fever
depending on EKGs of 402 patients with fever and 909 others without
fever, Eight of 402 patients with fever, but only 1 of 909 afebrile
patients, had a type I Brugada pattern. Thus, a type I Brugada pattern
was 20 times more prevalent among febrile patients (2% vs 0.1%, p=
.0001). All patients with fever-induced type I Brugada pattern were
asymptomatic and remained so during 30 months of follow-up. The study
concluded that type I Brugada pattern is definitively more common among
patients with fever, suggesting that asymptomatic Brugada pattern is
more prevalent than previously estimated (4).