<s>
Electrocardiography	B-Application
in	O
suspected	O
myocardial	O
infarction	O
has	O
the	O
main	O
purpose	O
of	O
detecting	O
ischemia	O
or	O
acute	O
coronary	O
injury	O
in	O
emergency	O
department	O
populations	O
coming	O
for	O
symptoms	O
of	O
myocardial	O
infarction	O
(	O
MI	O
)	O
.	O
</s>
<s>
The	O
standard	O
12	B-Application
lead	I-Application
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
has	O
several	O
limitations	O
.	O
</s>
<s>
An	O
ECG	B-Application
represents	O
a	O
brief	O
sample	O
in	O
time	O
.	O
</s>
<s>
Because	O
unstable	O
ischemic	O
syndromes	O
have	O
rapidly	O
changing	O
supply	O
versus	O
demand	O
characteristics	O
,	O
a	O
single	O
ECG	B-Application
may	O
not	O
accurately	O
represent	O
the	O
entire	O
picture	O
.	O
</s>
<s>
It	O
is	O
therefore	O
desirable	O
to	O
obtain	O
serial	O
12	B-Application
lead	I-Application
ECGs	I-Application
,	O
particularly	O
if	O
the	O
first	O
ECG	B-Application
is	O
obtained	O
during	O
a	O
pain-free	O
episode	O
.	O
</s>
<s>
The	O
standard	O
12	B-Application
lead	I-Application
ECG	I-Application
also	O
does	O
not	O
directly	O
examine	O
the	O
right	O
ventricle	O
,	O
and	O
is	O
relatively	O
poor	O
at	O
examining	O
the	O
posterior	O
basal	O
and	O
lateral	O
walls	O
of	O
the	O
left	O
ventricle	O
.	O
</s>
<s>
In	O
particular	O
,	O
acute	O
myocardial	O
infarction	O
in	O
the	O
distribution	O
of	O
the	O
circumflex	O
artery	O
is	O
likely	O
to	O
produce	O
a	O
nondiagnostic	O
ECG	B-Application
.	O
</s>
<s>
The	O
use	O
of	O
additional	O
ECG	B-Application
leads	O
like	O
right-sided	O
leads	O
V3R	O
and	O
V4R	O
and	O
posterior	O
leads	O
V7	O
,	O
V8	O
,	O
and	O
V9	O
may	O
improve	O
sensitivity	O
for	O
right	O
ventricular	O
and	O
posterior	O
myocardial	O
infarction	O
.	O
</s>
<s>
In	O
spite	O
of	O
these	O
limitations	O
,	O
the	O
12	B-Application
lead	I-Application
ECG	I-Application
stands	O
at	O
the	O
center	O
of	O
risk	O
stratification	O
for	O
the	O
patient	O
with	O
suspected	O
acute	O
myocardial	O
infarction	O
.	O
</s>
<s>
The	O
12	B-Application
lead	I-Application
ECG	I-Application
is	O
used	O
to	O
classify	O
MI	O
patients	O
into	O
one	O
of	O
three	O
groups	O
:	O
</s>
<s>
those	O
with	O
a	O
so-called	O
non-diagnostic	O
or	O
normal	B-Application
ECG	I-Application
.	O
</s>
<s>
However	O
,	O
a	O
normal	B-Application
ECG	I-Application
does	O
not	O
rule	O
out	O
acute	O
myocardial	O
infarction	O
.	O
</s>
<s>
The	O
2018	O
European	O
Society	O
of	O
Cardiology/American	O
College	O
of	O
Cardiology	O
Foundation/American	O
Heart	O
Association/World	O
Health	O
Federation	O
Universal	O
Definition	O
of	O
Myocardial	O
Infarction	O
for	O
the	O
ECG	B-Application
diagnosis	O
of	O
the	O
ST	O
segment	O
elevation	O
type	O
of	O
acute	O
myocardial	O
infarction	O
require	O
new	O
ST	O
elevation	O
at	O
J	O
point	O
of	O
at	O
least	O
1mm	O
(	O
0.1	O
mV	O
)	O
in	O
two	O
contiguous	O
leads	O
with	O
the	O
cut-points	O
:	O
≥1	O
mm	O
in	O
all	O
leads	O
other	O
than	O
leads	O
V2-V3	O
.	O
</s>
<s>
The	O
clinician	O
must	O
therefore	O
be	O
well	O
versed	O
in	O
recognizing	O
the	O
so-called	O
ECG	B-Application
mimics	O
of	O
acute	O
myocardial	O
infarction	O
,	O
which	O
include	O
left	O
ventricular	O
hypertrophy	O
,	O
left	O
bundle	O
branch	O
block	O
,	O
paced	B-Device
rhythm	I-Device
,	O
early	B-Algorithm
repolarization	I-Algorithm
,	O
pericarditis	O
,	O
hyperkalemia	O
,	O
and	O
ventricular	O
aneurysm	O
.	O
</s>
<s>
For	O
example	O
,	O
TIMI	O
scores	O
are	O
frequently	O
used	O
to	O
take	O
advantage	O
of	O
EKG	B-Application
findings	O
to	O
prognose	O
patients	O
with	O
MI	O
symptoms	O
.	O
</s>
<s>
Based	O
on	O
symptoms	O
and	O
electrocardiographic	B-Application
findings	O
,	O
practitioners	O
can	O
differentiate	O
between	O
unstable	O
angina	O
,	O
NSTEMI	O
and	O
STEMI	O
,	O
normally	O
in	O
the	O
emergency	O
room	O
setting	O
.	O
</s>
<s>
Other	O
calculators	O
such	O
as	O
the	O
GRACE	O
and	O
HEART	O
scores	O
,	O
assess	O
other	O
major	O
cardiac	O
events	O
using	O
electrocardiogram	B-Application
findings	O
,	O
both	O
predicting	O
mortality	O
rates	O
for	O
6	O
months	O
and	O
6	O
weeks	O
,	O
respectively	O
.	O
</s>
<s>
Sometimes	O
the	O
earliest	O
presentation	O
of	O
acute	O
myocardial	O
infarction	O
is	O
the	O
hyperacute	O
T	B-Algorithm
wave	I-Algorithm
,	O
which	O
is	O
treated	O
the	O
same	O
as	O
ST	O
segment	O
elevation	O
.	O
</s>
<s>
Hyperacute	O
T	B-Algorithm
waves	I-Algorithm
need	O
to	O
be	O
distinguished	O
from	O
the	O
peaked	O
T	B-Algorithm
waves	I-Algorithm
associated	O
with	O
hyperkalemia	O
.	O
</s>
<s>
Pathological	O
Q	B-Algorithm
waves	I-Algorithm
may	O
appear	O
within	O
hours	O
or	O
may	O
take	O
greater	O
than	O
24	O
hr	O
.	O
</s>
<s>
The	O
T	B-Algorithm
wave	I-Algorithm
will	O
generally	O
become	O
inverted	O
in	O
the	O
first	O
24	O
hours	O
,	O
as	O
the	O
ST	O
elevation	O
begins	O
to	O
resolve	O
.	O
</s>
<s>
Long	O
term	O
changes	O
of	O
ECG	B-Application
include	O
persistent	O
Q	B-Algorithm
waves	I-Algorithm
(	O
in	O
90%	O
of	O
cases	O
)	O
and	O
persistent	O
inverted	O
T	B-Algorithm
waves	I-Algorithm
.	O
</s>
