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[[Puzzle_2006_1_33 - Answer|Answer]]
[[Puzzle_2006_1_33 - Answer|Answer]]
[[Image:Puzzle_2006_1_33_fig2.jpg|Figure 2|thumb]]
[[Image:Puzzle_2006_1_33_fig3.jpg|Figure 3|thumb]]
The ECG shows sinus rhythm of 59 beats/min. Conduction
parameters are abnormal; the PQ interval is a
little over 200 msec and the QRS width is 120 msec
(nonspecific conduction delay). It should be noted
that the P-wave morphology is abnormal and that the
P-wave duration is at the upper limit of normal as well.
The electrical axis is at -30. The ST-T segments are
normal in all leads. QT interval is well within normal
limits and there is no right precordial ST elevation.
The chance that a familiar cardiac disorder is the cause
of the sudden death of a young (<40 years of age) close
relative is at least 40%.<cite>Tan</cite> Hence, the presence of an
abnormal ECG should alert the physician and specific
cardiac abnormalities should be looked for. A familial
structural cardiac abnormality seems unlikely because
no abnormalities were identified in his deceased brother
(idiopathic atrial fibrillation indicates the absence of
structural heart disease) nor in your patient. QT
prolongation is not present.
Delayed conduction in all cardiac compartments
should raise the suspicion of an abnormal cardiac
sodium channel, i.e. a sodium channelopathy which
includes Brugada syndrome, long-QT syndrome type
3 and isolated conduction disease or combinations
thereof. Brugada syndrome can be unmasked by
placing the right precordial leads one intercostal space
(ICS) more cranially (i.e. in the third ICS). In figures
2 and 3 the leads V5 and V6 have been replaced by leads
V1 and V2 positioned in the third ICS. A clear type 2
(saddle back) Brugada ECG becomes visible.<cite>Wilde</cite>
The strong suspicion of Brugada syndrome can now
be confirmed by a drug challenge. In this case, 100 mg
flecainide was infused (for protocol see reference 2)
and in addition to significant additional conduction
delay at all levels, the right precordial ST segments in
the third ICS turn into a coved type (figure 3). Brugada
syndrome should be diagnosed and DNA diagnostics
should be ordered. In this patient a mutation in the
SCN5a gene was identified (G1743E).
An electrophysiological study was performed and
ventricular fibrillation could reproducibly be induced.
An ICD was implanted.
==References==
<biblio>
#Tan pmid=15998675
#Wilde pmid=12448445
</biblio>
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