< Presentation of Case
>
A 43-year-old Taiwanese male
arrived at the emergency department (ED) after an episode of
syncope while at work. The event was witnessed by several of
the patient's co-workers, one of whom accompanied him to the
ED and described the event. According to the description
provided by his co-worker, the patient complained of nausea
and dizziness during the afternoon meeting. At around 3 pm,
the patient suddenly fell out of his chair and hit his head on
the floor. He was found unconscious without seizure-like
activities, including jerky body movements, tongue biting, or
incontinence. After a while, the patient regained
consciousness and was immediately fully alert without a period
of confusion or garbled speech. The patient recalled that this
was not the first episode and that he had experienced similar
episodes over the past few years, but this was the first time
he sought medical evaluation. The patient also indicated that
his father died suddenly in his 40s, but he could not recall
the cause of death. When presenting at the ED, the patient had
no specific complaints other than a bruise on his forehead
that resulted from the fall.
On physical examination, the
patient was awake and alert. The heart rate was 76 beats per
minute, the blood pressure 123/84 mm Hg, and the respiration
15 breaths per minute; the oxygen saturation was 100% while he
was breathing ambient air. A lesion of ecchymosis of 3.5 cm in
diameter was noted on his right forehead, with no hematoma,
laceration, or tenderness to palpation. Cardiac auscultation
revealed regular heart rhythm without murmurs or gallops and
the chest examination showed no abnormal breath sounds.
Results of the neurologic examination were also unremarkable,
including normal cranial nerve function and motor and sensory
functions.
A panel of
blood tests was performed (Tables). The results of the
complete blood cell (CBC) count as well as biochemistry were
unremarkable. Two electrocardiograms (ECG) were performed, one
while the patient was at the ED (see Figure
1) and the other 4 hours later (see Figure
2 ).
< Laboratory data
>
CBC/DC: (Time: 4:21pm, September 10th, 2006, at the
ED)
WBC /μL |
8100 |
Band % |
0 |
RBC M/μL |
4.22 |
Seg % |
59 |
Hb g/dL |
14.6 |
Lym % |
36 |
Hct % |
41.7 |
Mono % |
3 |
MCV fl |
88.3 |
Eos % |
2 |
PLT. /μL |
266000 |
Baso % |
0 |
Biochemistry: (Time: 4:21pm, September 10th, 2006, at the
ED)
Alb
g/dL |
3.8 |
T-Bil mg/dL |
0.6 |
BUN mg/dL |
18 |
K
mmol/L |
3.8 |
Cre
mg/dL |
0.9 |
ALT
U/L |
33 |
Glucose mg/dL |
108 |
Cl
mmol/L |
101 |
Na mmol/L |
142 |
AST U/L |
31 |
Mg
mmol/L |
0.9 |
Ca
mmol/L |
2.32 | Serial cardiac
enzyme levels (at the ED)
|
4:21am 09/10/2006 |
10:25m 09/10/2006 |
4:19pm 09/10/2006 |
10:22am 09/10/2006 |
CK (U/L) |
113 |
115 |
110 |
99 |
CK-MB (U/L) |
7 |
9 |
11 |
9 |
Troponin-I (U/L) |
0.05 |
0.04 |
0.05 |
0.02 |
Artery
blood gas (Time: 4:05 pm, September 10th, 2006, at the ED): pH: 7.41, PCO2: 39.6 mmHg, PO2: 88 mmHg,
HCO3-: 23.7 meq/L
Echocardiography (7:31pm, September 10th, 2008, at the
ED):
normal size of the left atrium and left ventricle (LV), with
good contractility, No tricupid regurgitation.
Coronary angiography (8:16am, September 11th, 2006): patent
coronary arteries
Magnetic resonance imaging of the heart (9:16am, September
12th, 2006): normal cardiac structure and systolic function of
the LV and right ventricle.
< Course and Treatment
>
A
consultation with an electrophysiologist was made, who
suggested admission of the patient for observation. The
follow-up ECG was normal (figure
2
), and his serial examinations of cardiac enzymes as well as
serum electrolytes were within the normal ranges for the next
24 hours (tables). He underwent an electrophysiologic study
(EPS) on September 12th, 2006, which showed inducible
ventricular fibrillation by rapid right ventricular pacing. It
was decided that an implantable cardioverter defibrillator
would be placed, considering the patient's family history of
sudden cardiac death, clinical presentations, ECG patterns and
EPS results. On September 13th, 2006, the patient was
discharged, and it was advised that his family members be made
aware of his diagnosis and
treatment.
< Discussion
>
The ECG findings (Figure 1 ) of this patient illustrates a
downsloping ST-segment elevation in leads V1-V3, accompanied
by a QRS morphology resembling that of a right bundle branch
block (RBBB), those of which are characteristic of a
Brugada-type pattern. In addition, the previous history of
multiple episodes of unexplained syncope, as well as sudden
cardiac death of his father suggests a diagnosis of the
Brugada syndrome. Sudden cardiac death is uncommon in
individuals with a structurally abnormal heart or without a
history of coronary artery disease. Causes of SCD in these
patients include: the Brugada syndrome, long-QT syndrome, and
preexcitation syndromes.
In 1992, Brugada and Brugada first reported a specific
clinical entity of idiopathic ventricular fibrillation (VF)
presenting with the ST segment elevation in leads V1 to V3,
with or without right bundle branch block, and normal QT
interval in the absence of structural heart disease or other
reversible causes [1]. It was also reported that these
patients died suddenly of VF and often in their sleep and
associated clinical features included syncopal episodes,
documented ventricular fibrillation, self-terminating
polymorphic ventricular tachycardia (VT), a family history of
sudden cardiac death in a relative aged less than 45 years,
and evidence of ST-segment elevation in family members.
Epidemiologic studies suggest that the disease might be
responsible for nearly half of all sudden cardiac death in
individuals without structural heart disease [2]. While the
prevalence of the disease may be dependent on factors such as
gender, age and ethnicity, the disease most commonly affects
men whose average age at presentation is 30 years and is the
most common cause of sudden cardiac death in young persons in
South Asia. [3] The Brugada syndrome is caused by an
autosomal-dominant genetic defect with incomplete penetrance
that results in dysfunction or loss of function of the sodium
channel, thereby reducing the sodium current available during
phases 0 (upstroke) and 1 (early repolarization), leading to
the development of malignant ventricular tachyarrhythmias,
which may lead to syncope, cardiac arrest, or sudden cardiac
death [4].
Underlying genetic components of the Brugada syndrome is
still under investigation. Brugada et al. suggested that as in
the long QT syndrome, the best candidate genes are those that
are responsible for the formation of the cardiac action
potential, namely the genes that encode for the cardiac ionic
channels [4], with approximately 20-30% of cases demonstrating
a loss-of-function mutation in the SCN5A gene [5, 6].
In many patients, electrocardiographic presentations of the
Brugada syndrome show transient normalization. This, however,
can be unmasked using sodium channel blockers such as
flecainide, ajmaline or procainamide [6].
The diagnosis of Brugada syndrome should be considered in
patients with a family history of sudden cardiac death, even
in the presence of an initial normal ECG. Admission is not
required for all patients presenting with syncope. However,
like the patient in this case study, those with previous
syncopal episodes as well as ECG abnormalities or a family
history of sudden cardiac death should be hospitalized for
investigations. To date, the only effective treatment of the
Brugada Syndrome is the implantation of an automatic
implantable cardioverter defibrillator (AICD). However, close
follow-up without intervention has been recommended for
asymptomatic patients with no family history of sudden cardiac
death.
In conclusion, this otherwise healthy patient with an
episode of sudden unexpected syncope received a diagnosis of
Brugada syndrome based on his family history of probable
sudden cardiac death, previous syncopal episodes as well as
ECG abnormalities. An AICD was placed without a formal EPS and
the patient was discharged on the second day of implantation.
< References
>
- Brugada P, Brugada J. Right bundle
branch block, persistent ST segment elevation and sudden
cardiac death: a distinct clinical and electrocardiographic
syndrome. A multicenter report. J Am Coll Cardiol
1992;20:1391-6.
- Brugada P, Brugada R, Brugada J.
The Brugada syndrome. Curr Cardiol Rep 2000; 2:507-14.
- Nademanee, K, et al.,
Arrhythmogenic marker for the sudden unexplained death
syndrome in Thai men. Circulation 1997;96:2595-600.
- Brugada J, Brugada P, Brugada R.
Brugada syndrome: the syndrome of right bundle branch block,
ST segment elevation in V1 to V3 and sudden death. Indian
Pacing Electrophysiol J 2001;1:6-11.
- Chen Q, et al. Genetic basis and
molecular mechanisms for idiopathic ventricular
fibrillation. Nature 1998;392:293-296.
- Gussak I, et al. The Brugada syndrome: clinical,
electrophysiologic and genetic aspects. J Am Coll Cardiol
1999;33:5-15.
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