<s>
A	O
cardiac	B-Algorithm
electrophysiology	I-Algorithm
study	O
(	O
EP	B-Algorithm
test	I-Algorithm
or	O
EP	B-Algorithm
study	I-Algorithm
)	O
is	O
a	O
minimally	O
invasive	O
procedure	O
using	O
catheters	O
introduced	O
through	O
a	O
vein	O
or	O
artery	O
to	O
record	O
electrical	O
activity	O
from	O
within	O
the	O
heart	O
.	O
</s>
<s>
This	O
electrical	O
activity	O
is	O
recorded	O
when	O
the	O
heart	O
is	O
in	O
a	O
normal	O
rhythm	O
(	O
sinus	O
rhythm	O
)	O
to	O
assess	O
the	O
conduction	B-Algorithm
system	I-Algorithm
of	I-Algorithm
the	I-Algorithm
heart	I-Algorithm
and	O
to	O
look	O
for	O
additional	O
electrical	O
connections	O
(	O
accessory	B-Algorithm
pathways	I-Algorithm
)	O
,	O
and	O
during	O
any	O
abnormal	B-Application
heart	I-Application
rhythms	I-Application
that	O
can	O
be	O
induced	O
.	O
</s>
<s>
EP	B-Algorithm
studies	I-Algorithm
are	O
used	O
to	O
investigate	O
the	O
cause	O
,	O
location	O
of	O
origin	O
,	O
and	O
best	O
treatment	O
for	O
various	O
abnormal	B-Application
heart	I-Application
rhythms	I-Application
,	O
and	O
are	O
often	O
followed	O
by	O
a	O
catheter	O
ablation	O
during	O
the	O
same	O
procedure	O
.	O
</s>
<s>
An	O
EP	B-Algorithm
study	I-Algorithm
is	O
typically	O
performed	O
in	O
an	O
EP	O
lab	O
or	O
cath	O
lab	O
.	O
</s>
<s>
Once	O
the	O
catheter	O
is	O
in	O
and	O
all	O
preparations	O
are	O
complete	O
elsewhere	O
in	O
the	O
lab	O
,	O
the	O
EP	B-Algorithm
study	I-Algorithm
begins	O
.	O
</s>
<s>
The	O
electrophysiologist	O
begins	O
by	O
moving	O
the	O
electrodes	O
along	O
the	O
conduction	B-Algorithm
pathways	I-Algorithm
and	O
along	O
the	O
inner	O
walls	O
of	O
the	O
heart	O
,	O
measuring	O
the	O
electrical	O
activity	O
along	O
the	O
way	O
.	O
</s>
<s>
Then	O
the	O
electrophysiologist	O
tries	O
to	O
provoke	O
arrhythmias	B-Application
and	O
reproduce	O
any	O
conditions	O
that	O
have	O
resulted	O
in	O
the	O
patient	O
's	O
placement	O
in	O
the	O
study	O
.	O
</s>
<s>
Last	O
,	O
the	O
electrophysiologist	O
may	O
administer	O
various	O
drugs	O
(	O
proarrhythmic	O
agents	O
)	O
to	O
induce	O
arrhythmia	B-Application
(	O
inducibility	O
of	O
VT/VF	O
)	O
.	O
</s>
<s>
If	O
the	O
arrhythmia	B-Application
is	O
reproduced	O
by	O
the	O
drugs	O
(	O
inducible	O
)	O
,	O
the	O
electrophysiologist	O
will	O
search	O
out	O
the	O
source	O
of	O
the	O
abnormal	O
electrical	O
activity	O
.	O
</s>
<s>
If	O
at	O
any	O
step	O
during	O
the	O
EP	B-Algorithm
study	I-Algorithm
the	O
electrophysiologist	O
finds	O
the	O
source	O
of	O
the	O
abnormal	O
electrical	O
activity	O
,	O
they	O
may	O
try	O
to	O
ablate	O
the	O
cells	O
that	O
are	O
misfiring	O
.	O
</s>
<s>
More	O
severe	O
but	O
relatively	O
rare	O
complications	O
include	O
:	O
damage	O
or	O
trauma	O
to	O
a	O
blood	O
vessel	O
,	O
which	O
could	O
require	O
repair	O
;	O
infection	O
from	O
the	O
skin	O
puncture	O
or	O
from	O
the	O
catheter	O
itself	O
;	O
cardiac	O
perforation	O
,	O
causing	O
blood	O
to	O
leak	O
into	O
the	O
sac	O
around	O
the	O
heart	O
and	O
compromising	O
the	O
heart	O
's	O
pumping	O
action	O
,	O
requiring	O
removal	O
using	O
a	O
needle	O
under	O
the	O
breast	O
bone	O
(	O
pericardiocentesis	O
)	O
;	O
hematoma	O
at	O
the	O
site(s )	O
of	O
the	O
puncture(s )	O
;	O
induction	O
of	O
a	O
dangerous	O
cardiac	B-Algorithm
rhythm	I-Algorithm
requiring	O
an	O
external	O
shock(s )	O
;	O
a	O
clot	O
may	O
be	O
dislodged	O
,	O
which	O
may	O
travel	O
to	O
a	O
distant	O
organ	O
and	O
impede	O
blood	O
flow	O
or	O
cause	O
a	O
stroke	O
;	O
myocardial	O
infarction	O
;	O
unanticipated	O
reactions	O
to	O
the	O
medications	O
used	O
during	O
the	O
procedure	O
;	O
damage	O
to	O
the	O
conduction	B-Algorithm
system	I-Algorithm
,	O
requiring	O
a	O
permanent	O
pacemaker	O
;	O
death	O
.	O
</s>
