Brugada Syndrome

PEDRO AND JOSEP BRUGADA DESCRIBED A
cardiac condition in 1992 characterized by a typical
ECG pattern and a high incidence of sudden death particularly
in younger individuals. The Brugada syndrome is a
congenital disorder of sodium cardiac channel function. It
is prevalent in Southeast Asia. Rare deaths have occurred
during sleep sometimes associated with nightmares. The
syndrome has variety of names in different countries:
Bangungut (scream followed by sudden death) in the
Philippines, Lai Tai in Thailand, and Pokkuri (unexpected
death at night) in Japan. Apparently in Thailand
unexplained sudden cardiac death is the leading cause of
death in young men, and approximately 40% of these
patients have a family history of sudden deaths; an
estimated incidence of 1 sudden death per 1000 persons
per year. The Brugada VCG phenotype has been estimated
to be up to 1.4% in Japan The typical ECG pattern
may be intermittent, and is found in 0.15% of Japanese
adults, which is associated with a greater then 50-fold
increase in the risk of unexpected death; the incidence
is reportedly ninefold higher in Japanese men than in
women.

Although much less common than in south–eastern Asia
this syndrome is not rare in western countries and in North
America.

I. CLINICAL FEATURES
Symptoms, particularly syncope and sudden death, usually
appear between the ages of 40 and 50. These symptoms
occur with no warning. In one study of 163 patients in
which ventricular fibrillation occurred in 22% percent, the
following observations were made: 12:1 male to female
ratio, 58% of Asian origin, and mean age at first abnormal
heart rhythm detected was 22–65, but occurred more often
in the 40–50 age group. Most of these patients had a
family history of syncope, sudden death, or abnormal
ECG changes.

In Brugada syndrome sudden cardiac death is often
preceded by several episodes of syncope. Brugada syndrome
is believed to cause approximately 30% of all cases
of ventricular fibrillation of unknown cause. Remme et al.
reported that the vast majority of patients showed no
evidence of structural heart disease but the electrical system
has a minor derangement, probably in the bundle of
His–Purkinje electrical conducting system that in some
individuals can trigger ventricular fibrillation and death.
In these patients the ECG is diagnostic and shows a
distinctive type of right bundle branch block. The ST
segment is elevated in chest leads V1, V2, and V3 where
the right bundle branch pattern is usually seen. Figures 1–5
show the ECG tracing in a patient with Brugada syndrome.
The elevated ST segment has a curious convex
curve or a coved and saddle back shape. The ECG is
abnormal but the heart is structurally normal. Antiarrhythmic
agents are not effective in preventing ventricular
fibrillation in these patients and implantation of a cardioverter
defibrillator is advisable to prevent sudden death.

II. PERSPECTIVE
The exact mechanism of the electrocardiographic changes
and the development of ventricular fibrillation and sudden
death remain undetermined. Electrically active cardiac cells
possess sodium channels; an outward sodium current is
counterbalanced by an inward sodium current. It appears
that in this syndrome the inward current is attenuated
and some of the electrocardiographic features can be partly
explained based on changes in sodium currents. The
syndrome is a disorder of sodium cardiac channel function
that triggers the electrocardiographic changes and
malignant arrhythmias, particularly ventricular fibrillation.
Mutations in a gene responsible for the sodium channel
have been identified in some families with this syndrome.
More than three different mutations on the cardiac
sodium channel gene SCN5A on chromosome 3 have been
described. Mutations on other genes are being sought.
Further research is required in this area and its results
are of extreme importance to prevent deaths in young
individuals.

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