<s>
Ventricular	B-Application
tachycardia	I-Application
(	O
V-tach	B-Application
or	O
VT	O
)	O
is	O
a	O
fast	B-Application
heart	I-Application
rate	I-Application
arising	O
from	O
the	O
lower	O
chambers	O
of	O
the	O
heart	O
.	O
</s>
<s>
Short	O
periods	O
may	O
occur	O
without	O
symptoms	O
,	O
or	O
present	O
with	O
lightheadedness	O
,	O
palpitations	B-Algorithm
,	O
or	O
chest	O
pain	O
.	O
</s>
<s>
Ventricular	B-Application
tachycardia	I-Application
may	O
result	O
in	O
ventricular	O
fibrillation	O
(	O
VF	O
)	O
and	O
turn	O
into	O
cardiac	O
arrest	O
.	O
</s>
<s>
Ventricular	B-Application
tachycardia	I-Application
can	O
occur	O
due	O
to	O
coronary	O
heart	O
disease	O
,	O
aortic	O
stenosis	O
,	O
cardiomyopathy	O
,	O
electrolyte	O
problems	O
,	O
or	O
a	O
heart	O
attack	O
.	O
</s>
<s>
Diagnosis	O
is	O
by	O
an	O
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
showing	O
a	O
rate	O
of	O
greater	O
than	O
120	O
beats	O
per	O
minute	O
and	O
at	O
least	O
three	O
wide	O
QRS	B-Algorithm
complexes	I-Algorithm
in	O
a	O
row	O
.	O
</s>
<s>
The	O
term	O
ventricular	O
arrhythmia	O
refers	O
to	O
the	O
group	O
of	O
abnormal	O
cardiac	O
rhythms	O
originating	O
from	O
the	O
ventricle	O
,	O
which	O
includes	O
ventricular	B-Application
tachycardia	I-Application
,	O
ventricular	O
fibrillation	O
,	O
and	O
torsades	B-Algorithm
de	I-Algorithm
pointes	I-Algorithm
.	O
</s>
<s>
In	O
those	O
who	O
have	O
normal	O
blood	O
pressure	O
and	O
strong	O
pulse	O
,	O
the	O
antiarrhythmic	B-Algorithm
medication	I-Algorithm
procainamide	O
may	O
be	O
used	O
.	O
</s>
<s>
In	O
those	O
in	O
cardiac	O
arrest	O
due	O
to	O
ventricular	B-Application
tachycardia	I-Application
,	O
cardiopulmonary	O
resuscitation	O
(	O
CPR	O
)	O
and	O
defibrillation	O
is	O
recommended	O
.	O
</s>
<s>
While	O
waiting	O
for	O
a	O
defibrillator	O
,	O
a	O
precordial	O
thump	O
may	O
be	O
attempted	O
(	O
However	O
reserved	O
to	O
those	O
who	O
have	O
the	O
prior	O
experience	O
of	O
doing	O
so	O
)	O
in	O
those	O
on	O
a	O
heart	O
monitor	O
who	O
are	O
seen	O
going	O
into	O
an	O
unstable	O
ventricular	B-Application
tachycardia	I-Application
.	O
</s>
<s>
In	O
those	O
with	O
cardiac	O
arrest	O
due	O
to	O
ventricular	B-Application
tachycardia	I-Application
,	O
survival	O
is	O
about	O
45%	O
.	O
</s>
<s>
Short	O
periods	O
may	O
occur	O
without	O
symptoms	O
or	O
present	O
with	O
lightheadedness	O
,	O
palpitations	B-Algorithm
,	O
or	O
chest	O
pain	O
.	O
</s>
<s>
Ventricular	B-Application
tachycardia	I-Application
may	O
turn	O
into	O
ventricular	O
fibrillation	O
and	O
can	O
result	O
in	O
cardiac	O
arrest	O
.	O
</s>
<s>
Ventricular	B-Application
tachycardia	I-Application
can	O
occur	O
due	O
to	O
coronary	O
heart	O
disease	O
,	O
aortic	O
stenosis	O
,	O
cardiomyopathy	O
,	O
electrolyte	O
problems	O
(	O
e.g.	O
,	O
low	O
blood	O
levels	O
of	O
magnesium	O
or	O
potassium	O
)	O
,	O
inherited	O
channelopathies	O
(	O
e.g.	O
,	O
long-QT	O
syndrome	O
)	O
,	O
catecholaminergic	O
polymorphic	B-Application
ventricular	I-Application
tachycardia	I-Application
,	O
arrhythmogenic	O
right	O
ventricular	O
dysplasia	O
,	O
alcohol	O
withdrawal	O
syndrome	O
(	O
typically	O
following	O
atrial	B-Application
fibrillation	I-Application
)	O
,	O
or	O
a	O
myocardial	O
infarction	O
.	O
</s>
<s>
The	O
morphology	O
of	O
the	O
tachycardia	B-Application
depends	O
on	O
its	O
cause	O
and	O
the	O
origin	O
of	O
the	O
re-entry	O
electrical	O
circuit	O
in	O
the	O
heart	O
.	O
</s>
<s>
In	O
monomorphic	O
ventricular	B-Application
tachycardia	I-Application
,	O
the	O
shape	O
of	O
each	O
heart	O
beat	O
on	O
the	O
ECG	B-Application
looks	O
the	O
same	O
because	O
the	O
impulse	O
is	O
either	O
being	O
generated	O
from	O
increased	O
automaticity	O
of	O
a	O
single	O
point	O
in	O
either	O
the	O
left	O
or	O
the	O
right	O
ventricle	O
,	O
or	O
due	O
to	O
a	O
reentry	O
circuit	O
within	O
the	O
ventricle	O
.	O
</s>
<s>
The	O
most	O
common	O
cause	O
of	O
monomorphic	O
ventricular	B-Application
tachycardia	I-Application
is	O
scarring	O
of	O
the	O
heart	O
muscle	O
from	O
a	O
previous	O
myocardial	O
infarction	O
(	O
heart	O
attack	O
)	O
.	O
</s>
<s>
This	O
scar	O
cannot	O
conduct	O
electrical	O
activity	O
,	O
so	O
there	O
is	O
a	O
potential	O
circuit	O
around	O
the	O
scar	O
that	O
results	O
in	O
the	O
tachycardia	B-Application
.	O
</s>
<s>
This	O
is	O
similar	O
to	O
the	O
re-entrant	O
circuits	O
that	O
are	O
the	O
cause	O
of	O
atrial	O
flutter	O
and	O
the	O
re-entrant	O
forms	O
of	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
.	O
</s>
<s>
Polymorphic	B-Application
ventricular	I-Application
tachycardia	I-Application
,	O
on	O
the	O
other	O
hand	O
,	O
is	O
most	O
commonly	O
caused	O
by	O
abnormalities	O
of	O
ventricular	O
muscle	O
repolarization	O
.	O
</s>
<s>
The	O
predisposition	O
to	O
this	O
problem	O
usually	O
manifests	O
on	O
the	O
ECG	B-Application
as	O
a	O
prolongation	O
of	O
the	O
QT	B-Algorithm
interval	I-Algorithm
.	O
</s>
<s>
Congenital	O
problems	O
include	O
long	O
QT	O
syndrome	O
and	O
catecholaminergic	O
polymorphic	B-Application
ventricular	I-Application
tachycardia	I-Application
.	O
</s>
<s>
Class	O
III	O
anti-arrhythmic	B-Algorithm
drugs	I-Algorithm
such	O
as	O
sotalol	O
and	O
amiodarone	O
prolong	O
the	O
QT	B-Algorithm
interval	I-Algorithm
and	O
may	O
in	O
some	O
circumstances	O
be	O
pro-arrhythmic	O
.	O
</s>
<s>
The	O
diagnosis	O
of	O
ventricular	B-Application
tachycardia	I-Application
is	O
made	O
based	O
on	O
the	O
rhythm	O
seen	O
on	O
either	O
a	O
12-lead	B-Application
ECG	I-Application
or	O
a	O
telemetry	O
rhythm	O
strip	O
.	O
</s>
<s>
It	O
may	O
be	O
very	O
difficult	O
to	O
differentiate	O
between	O
ventricular	B-Application
tachycardia	I-Application
and	O
a	O
wide-complex	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
in	O
some	O
cases	O
.	O
</s>
<s>
In	O
particular	O
,	O
supraventricular	B-Algorithm
tachycardias	I-Algorithm
with	O
aberrant	O
conduction	O
from	O
a	O
pre-existing	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
are	O
commonly	O
misdiagnosed	O
as	O
ventricular	B-Application
tachycardia	I-Application
.	O
</s>
<s>
Other	O
rarer	O
phenomena	O
include	O
Ashman	B-Algorithm
beats	I-Algorithm
and	O
antidromic	B-Algorithm
atrioventricular	I-Algorithm
re-entry	I-Algorithm
tachycardias	I-Algorithm
.	O
</s>
<s>
Various	O
diagnostic	O
criteria	O
have	O
been	O
developed	O
to	O
determine	O
whether	O
a	O
wide	B-Application
complex	I-Application
tachycardia	I-Application
is	O
ventricular	B-Application
tachycardia	I-Application
or	O
a	O
more	O
benign	O
rhythm	O
.	O
</s>
<s>
In	O
addition	O
to	O
these	O
diagnostic	O
criteria	O
,	O
if	O
the	O
individual	O
has	O
a	O
history	O
of	O
a	O
myocardial	O
infarction	O
,	O
congestive	O
heart	O
failure	O
,	O
or	O
recent	O
angina	O
,	O
the	O
wide	B-Application
complex	I-Application
tachycardia	I-Application
is	O
much	O
more	O
likely	O
to	O
be	O
ventricular	B-Application
tachycardia	I-Application
.	O
</s>
<s>
The	O
proper	O
diagnosis	O
is	O
important	O
,	O
as	O
the	O
misdiagnosis	O
of	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
when	O
ventricular	B-Application
tachycardia	I-Application
is	O
present	O
is	O
associated	O
with	O
worse	O
prognosis	O
.	O
</s>
<s>
This	O
is	O
particularly	O
true	O
if	O
calcium	O
channel	O
blockers	O
,	O
such	O
as	O
verapamil	O
,	O
are	O
used	O
to	O
attempt	O
to	O
terminate	O
a	O
presumed	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
wisest	O
to	O
assume	O
that	O
all	O
wide	B-Application
complex	I-Application
tachycardia	I-Application
is	O
VT	O
until	O
proven	O
otherwise	O
.	O
</s>
<s>
ECG	B-Application
features	O
of	O
Ventricular	B-Application
Tachycardia	I-Application
in	O
addition	O
to	O
the	O
increased	B-Application
Heart	I-Application
rate	I-Application
are	O
:	O
</s>
<s>
Capture	O
beats	O
(	O
normal	O
QRS	B-Algorithm
complex	I-Algorithm
in	O
between	O
when	O
the	O
Heart	O
pick	O
up	O
the	O
sinus	O
rhythm	O
from	O
the	O
impulses	O
generated	O
by	O
the	O
SA	O
node	O
)	O
,	O
fusion	O
beats	O
(	O
due	O
to	O
the	O
fusion	O
of	O
the	O
Abnormal	O
and	O
the	O
Normal	O
QRS	B-Algorithm
complexes	I-Algorithm
)	O
which	O
has	O
a	O
unique	O
morphology	O
.	O
</s>
<s>
Ventricular	B-Application
tachycardia	I-Application
can	O
be	O
classified	O
based	O
on	O
its	O
morphology	O
:	O
</s>
<s>
Monomorphic	O
ventricular	B-Application
tachycardia	I-Application
means	O
that	O
the	O
appearance	O
of	O
all	O
the	O
beats	O
match	O
each	O
other	O
in	O
each	O
lead	O
of	O
a	O
surface	O
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
.	O
</s>
<s>
Scar-related	O
monomorphic	O
ventricular	B-Application
tachycardia	I-Application
is	O
the	O
most	O
common	O
type	O
and	O
a	O
frequent	O
cause	O
of	O
death	O
in	O
patients	O
having	O
survived	O
a	O
heart	O
attack	O
,	O
especially	O
if	O
they	O
have	O
weak	O
heart	O
muscle	O
.	O
</s>
<s>
Right	O
ventricular	O
outflow	O
tract	O
(	O
RVOT	O
)	O
tachycardia	B-Application
is	O
a	O
type	O
of	O
monomorphic	O
ventricular	B-Application
tachycardia	I-Application
originating	O
in	O
the	O
right	O
ventricular	O
outflow	O
tract	O
.	O
</s>
<s>
RVOT	O
morphology	O
refers	O
to	O
the	O
characteristic	O
pattern	O
of	O
this	O
type	O
of	O
tachycardia	B-Application
on	O
an	O
ECG	B-Application
.	O
</s>
<s>
The	O
source	O
of	O
the	O
re-entry	O
circuit	O
can	O
be	O
identified	O
by	O
evaluating	O
the	O
morphology	O
of	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
in	O
the	O
V1	O
lead	O
of	O
a	O
surface	O
ECG	B-Application
.	O
</s>
<s>
If	O
the	O
R	B-Algorithm
wave	I-Algorithm
is	O
dominant	O
(	O
consistent	O
with	O
a	O
right	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
morphology	O
)	O
,	O
this	O
indicates	O
the	O
origin	O
of	O
the	O
VT	O
is	O
the	O
left	O
ventricle	O
.	O
</s>
<s>
Conversely	O
,	O
if	O
the	O
S	O
wave	O
is	O
dominant	O
(	O
consistent	O
with	O
a	O
left	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
morphology	O
,	O
this	O
is	O
consistent	O
with	O
VT	O
originating	O
from	O
the	O
right	O
ventricle	O
or	O
interventricular	O
septum	O
.	O
</s>
<s>
Polymorphic	B-Application
ventricular	I-Application
tachycardia	I-Application
,	O
on	O
the	O
other	O
hand	O
,	O
has	O
beat-to-beat	O
variations	O
in	O
morphology	O
.	O
</s>
<s>
This	O
may	O
appear	O
as	O
a	O
cyclical	O
progressive	O
change	O
in	O
cardiac	O
axis	O
,	O
previously	O
referred	O
to	O
by	O
its	O
French	O
name	O
torsades	B-Algorithm
de	I-Algorithm
pointes	I-Algorithm
(	O
"	O
twisting	O
of	O
the	O
spikes	O
"	O
)	O
.	O
</s>
<s>
However	O
,	O
at	O
the	O
current	O
time	O
,	O
the	O
term	O
torsades	B-Algorithm
de	I-Algorithm
pointes	I-Algorithm
is	O
reserved	O
for	O
polymorphic	O
VT	O
occurring	O
in	O
the	O
context	O
of	O
a	O
prolonged	O
resting	O
QT	B-Algorithm
interval	I-Algorithm
.	O
</s>
<s>
Another	O
way	O
to	O
classify	O
ventricular	B-Application
tachycardias	I-Application
is	O
the	O
duration	O
of	O
the	O
episodes	O
:	O
Three	O
or	O
more	O
beats	O
in	O
a	O
row	O
on	O
an	O
ECG	B-Application
that	O
originate	O
from	O
the	O
ventricle	O
at	O
a	O
rate	O
of	O
more	O
than	O
120	O
beats	O
per	O
minute	O
constitute	O
a	O
ventricular	B-Application
tachycardia	I-Application
.	O
</s>
<s>
If	O
the	O
rhythm	O
lasts	O
more	O
than	O
30	O
seconds	O
,	O
it	O
is	O
known	O
as	O
a	O
sustained	B-Application
ventricular	I-Application
tachycardia	I-Application
(	O
even	O
if	O
it	O
terminates	O
on	O
its	O
own	O
after	O
30	O
seconds	O
)	O
.	O
</s>
<s>
A	O
third	O
way	O
to	O
classify	O
ventricular	B-Application
tachycardia	I-Application
is	O
on	O
the	O
basis	O
of	O
its	O
symptoms	O
:	O
Pulseless	O
VT	O
is	O
associated	O
with	O
no	O
effective	O
cardiac	O
output	O
,	O
hence	O
,	O
no	O
effective	O
pulse	O
,	O
and	O
is	O
a	O
cause	O
of	O
cardiac	O
arrest	O
(	O
see	O
also	O
:	O
pulseless	O
electrical	O
activity	O
 [ PEA ] 	O
)	O
.	O
</s>
<s>
Occasionally	O
in	O
ventricular	B-Application
tachycardia	I-Application
,	O
supraventricular	O
impulses	O
are	O
conducted	O
to	O
the	O
ventricles	O
,	O
generating	O
QRS	B-Algorithm
complexes	I-Algorithm
with	O
normal	O
or	O
aberrant	O
supraventricular	O
morphology	O
(	O
ventricular	O
capture	O
)	O
.	O
</s>
<s>
Less	O
common	O
is	O
ventricular	B-Application
tachycardia	I-Application
that	O
occurs	O
in	O
individuals	O
with	O
structurally	O
normal	O
hearts	O
.	O
</s>
<s>
This	O
is	O
known	O
as	O
idiopathic	O
ventricular	B-Application
tachycardia	I-Application
and	O
in	O
the	O
monomorphic	O
form	O
coincides	O
with	O
little	O
or	O
no	O
increased	O
risk	O
of	O
sudden	O
cardiac	O
death	O
.	O
</s>
<s>
In	O
general	O
,	O
idiopathic	O
ventricular	B-Application
tachycardia	I-Application
occurs	O
in	O
younger	O
individuals	O
diagnosed	O
with	O
VT	O
.	O
</s>
<s>
The	O
treatment	O
for	O
stable	O
VT	O
is	O
tailored	O
to	O
the	O
specific	O
person	O
,	O
with	O
regard	O
to	O
how	O
well	O
the	O
individual	O
tolerates	O
episodes	O
of	O
ventricular	B-Application
tachycardia	I-Application
,	O
how	O
frequently	O
episodes	O
occur	O
,	O
their	O
comorbidities	O
,	O
and	O
their	O
wishes	O
.	O
</s>
<s>
Pacing	O
the	O
ventricle	O
at	O
a	O
rate	O
faster	O
than	O
the	O
underlying	O
tachycardia	B-Application
can	O
sometimes	O
be	O
effective	O
in	O
terminating	O
the	O
rhythm	O
.	O
</s>
<s>
As	O
a	O
low	O
magnesium	O
level	O
in	O
the	O
blood	O
is	O
a	O
common	O
cause	O
of	O
VT	O
,	O
magnesium	O
sulfate	O
can	O
be	O
given	O
for	O
torsades	B-Algorithm
de	I-Algorithm
pointes	I-Algorithm
or	O
if	O
a	O
low	O
blood	O
magnesium	O
level	O
is	O
found/suspected	O
.	O
</s>
<s>
Long-term	O
anti-arrhythmic	B-Algorithm
therapy	O
may	O
be	O
indicated	O
to	O
prevent	O
recurrence	O
of	O
VT	O
.	O
Beta-blockers	O
and	O
a	O
number	O
of	O
class	O
III	O
anti-arrhythmics	B-Algorithm
are	O
commonly	O
used	O
,	O
such	O
as	O
the	O
beta-blockers	O
carvedilol	O
,	O
metoprolol	O
,	O
and	O
bisoprolol	O
,	O
and	O
the	O
Potassium-Channel-Blockers	O
amiodarone	O
,	O
dronedarone	O
,	O
bretylium	O
,	O
sotalol	O
,	O
ibutilide	O
,	O
and	O
dofetilide	O
.	O
</s>
<s>
Antiarrhythmic	B-Algorithm
medications	I-Algorithm
can	O
reduce	O
the	O
frequency	O
of	O
ICD	O
therapies	O
,	O
but	O
have	O
efficacy	O
varies	O
and	O
side	O
effects	O
can	O
be	O
significant	O
.	O
</s>
