<s>
Junctional	B-Algorithm
ectopic	I-Algorithm
tachycardia	I-Algorithm
(	O
JET	O
)	O
is	O
a	O
rare	O
syndrome	O
of	O
the	O
heart	O
that	O
manifests	O
in	O
patients	O
recovering	O
from	O
heart	O
surgery	O
.	O
</s>
<s>
It	O
is	O
characterized	O
by	O
cardiac	B-Application
arrhythmia	I-Application
,	O
or	O
irregular	O
beating	O
of	O
the	O
heart	O
,	O
caused	O
by	O
abnormal	O
conduction	O
from	O
or	O
through	O
the	O
atrioventricular	B-Algorithm
node	O
(	O
AV	O
node	O
)	O
.	O
</s>
<s>
In	O
newborns	O
and	O
infants	O
up	O
to	O
6	O
weeks	O
old	O
,	O
the	O
disease	O
may	O
also	O
be	O
referred	O
to	O
as	O
His	B-Algorithm
bundle	I-Algorithm
tachycardia	I-Algorithm
or	O
congenital	O
JET	O
.	O
</s>
<s>
In	O
normal	O
individuals	O
,	O
electrical	O
activity	O
in	O
the	O
heart	O
is	O
initiated	O
in	O
the	O
sinoatrial	O
(	O
SA	O
)	O
node	O
(	O
located	O
in	O
the	O
right	O
atrium	O
)	O
,	O
propagates	O
to	O
the	O
atrioventricular	B-Algorithm
(	O
AV	O
)	O
node	O
,	O
and	O
then	O
through	O
the	O
bundle	B-Algorithm
of	I-Algorithm
His	I-Algorithm
to	O
the	O
ventricles	O
of	O
the	O
heart	O
.	O
</s>
<s>
This	O
function	O
of	O
the	O
AV	O
node	O
is	O
important	O
,	O
because	O
if	O
the	O
signals	O
generated	O
in	O
the	O
atria	O
of	O
the	O
heart	O
were	O
to	O
increase	O
in	O
rate	O
(	O
as	O
they	O
do	O
during	O
atrial	B-Application
fibrillation	I-Application
or	O
atrial	O
flutter	O
)	O
,	O
the	O
AV	O
node	O
will	O
limit	O
the	O
electrical	O
activity	O
that	O
conducts	O
to	O
the	O
ventricles	O
.	O
</s>
<s>
This	O
is	O
manifest	O
on	O
the	O
ECG	B-Application
as	O
the	O
PR	O
interval	O
,	O
which	O
is	O
about	O
less	O
than	O
200	O
milliseconds	O
,	O
the	O
time	O
from	O
activation	O
of	O
the	O
atria	O
(	O
manifest	O
as	O
the	O
P	B-Algorithm
wave	I-Algorithm
)	O
and	O
activation	O
of	O
the	O
ventricles	O
(	O
manifest	O
as	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
)	O
.	O
</s>
<s>
The	O
cause	O
of	O
the	O
arrhythmia	B-Application
,	O
the	O
ectopic	O
focus	O
,	O
is	O
usually	O
near	O
the	O
AV	O
node	O
in	O
the	O
triangle	O
of	O
Koch	O
(	O
a	O
rough	O
triangle	O
with	O
points	O
at	O
the	O
coronary	O
sinus	O
,	O
the	O
tendon	O
of	O
Todaro	O
,	O
and	O
the	O
tricuspid	O
valve	O
)	O
.	O
</s>
<s>
Patients	O
of	O
heart	O
surgery	O
may	O
experience	O
an	O
accelerated	O
narrow	B-Algorithm
complex	I-Algorithm
tachycardia	I-Algorithm
,	O
usually	O
within	O
the	O
first	O
24	O
–	O
48	O
hours	O
(	O
but	O
occasionally	O
longer	O
)	O
after	O
surgery	O
.	O
</s>
<s>
This	O
syndrome	O
,	O
which	O
may	O
also	O
referred	O
to	O
as	O
His	B-Algorithm
bundle	I-Algorithm
tachycardia	I-Algorithm
,	O
is	O
resistant	O
to	O
therapy	O
and	O
can	O
be	O
difficult	O
to	O
treat	O
.	O
</s>
<s>
JET	O
is	O
most	O
commonly	O
diagnosed	O
using	O
a	O
12-lead	B-Application
ECG	I-Application
.	O
</s>
<s>
The	O
QRS	B-Algorithm
complexes	I-Algorithm
are	O
usually	O
narrow	O
,	O
but	O
may	O
be	O
broad	O
if	O
a	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
is	O
present	O
.	O
</s>
<s>
There	O
may	O
a	O
1:1	O
relationship	O
between	O
atria	O
and	O
ventricular	O
activity	O
with	O
a	O
short	O
RP	O
interval	O
,	O
or	O
atrioventricular	B-Algorithm
dissociation	O
with	O
slower	O
atrial	O
than	O
ventricular	O
rates	O
if	O
the	O
AV	O
node	O
is	O
unable	O
to	O
conduct	O
from	O
the	O
ventricles	O
to	O
the	O
atria	O
.	O
</s>
<s>
The	O
differential	O
diagnosis	O
of	O
JET	O
includes	O
other	O
forms	O
of	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
,	O
most	O
commonly	O
atrioventricular	B-Algorithm
nodal	I-Algorithm
reentrant	I-Algorithm
tachycardia	I-Algorithm
(	O
AVNRT	B-Algorithm
)	O
.	O
</s>
<s>
The	O
response	O
to	O
adenosine	O
in	O
JET	O
is	O
a	O
temporary	O
loss	O
of	O
conduction	O
to	O
the	O
atria	O
leading	O
to	O
continuation	O
of	O
the	O
tachycardia	O
but	O
with	O
atrioventricular	B-Algorithm
dissociation	O
.	O
</s>
<s>
In	O
contrast	O
,	O
administration	O
of	O
adenosine	O
in	O
AVNRT	B-Algorithm
will	O
usually	O
terminate	O
the	O
arrhythmia	B-Application
.	O
</s>
<s>
The	O
diagnosis	O
can	O
be	O
conclusively	O
proven	O
by	O
performing	O
an	O
invasive	O
electrophysiological	B-Algorithm
study	I-Algorithm
.	O
</s>
<s>
Treatment	O
is	O
aimed	O
at	O
slowing	O
the	O
rate	O
by	O
correcting	O
acidosis	O
,	O
correcting	O
electrolytes	O
(	O
especially	O
magnesium	O
and	O
calcium	O
)	O
,	O
cooling	O
the	O
patient	O
,	O
and	O
antiarrhythmic	B-Algorithm
medications	I-Algorithm
.	O
</s>
<s>
Medications	O
used	O
to	O
treat	O
JET	O
include	O
beta-adrenoceptor	O
blockers	O
such	O
as	O
propranolol	O
,	O
calcium	O
channel	O
antagonists	O
such	O
as	O
verapamil	O
,	O
and	O
antiarrhythmics	B-Algorithm
such	O
as	O
flecainide	O
,	O
amiodarone	O
,	O
and	O
propafenone	O
.	O
</s>
<s>
This	O
occurs	O
more	O
frequently	O
when	O
treating	O
JET	O
than	O
other	O
forms	O
of	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
,	O
requiring	O
treatment	O
with	O
a	O
pacemaker	B-Device
in	O
5-10	O
%	O
of	O
ablations	O
for	O
JET	O
.	O
</s>
<s>
The	O
arrhythmia	B-Application
affects	O
2-22	O
%	O
of	O
children	O
depending	O
on	O
the	O
type	O
of	O
surgery	O
performed	O
,	O
with	O
higher	O
rates	O
seen	O
following	O
repair	O
of	O
Tetralogy	O
of	O
Fallot	O
,	O
and	O
lower	O
rates	O
following	O
the	O
repair	O
of	O
ventricular	O
septal	O
defects	O
and	O
arterial	O
switch	O
operations	O
.	O
</s>
<s>
Junctional	B-Algorithm
ectopic	I-Algorithm
tachycardia	I-Algorithm
derives	O
its	O
name	O
from	O
the	O
problem	O
it	O
causes	O
.	O
</s>
<s>
Ectopic	O
(	O
from	O
the	O
Greek	O
ektopos	O
,	O
meaning	O
"	O
out	O
of	O
place	O
"	O
)	O
refers	O
to	O
the	O
fact	O
that	O
the	O
ventricles	O
are	O
being	O
triggered	O
by	O
tissue	O
that	O
is	O
not	O
the	O
normal	O
pacemaker	B-Device
tissue	O
within	O
the	O
heart	O
.	O
</s>
<s>
By	O
this	O
definition	O
,	O
junctional	B-Algorithm
ectopic	I-Algorithm
tachycardia	I-Algorithm
is	O
an	O
abnormally	O
swift	O
heart	O
rhythm	O
due	O
to	O
cells	O
firing	O
within	O
the	O
heart	O
near	O
the	O
AV	O
node	O
.	O
</s>
