<s>
ST	B-Algorithm
elevation	I-Algorithm
refers	O
to	O
a	O
finding	O
on	O
an	O
electrocardiogram	B-Application
wherein	O
the	O
trace	O
in	O
the	O
ST	B-Algorithm
segment	I-Algorithm
is	O
abnormally	O
high	O
above	O
the	O
baseline	O
.	O
</s>
<s>
The	O
ST	B-Algorithm
segment	I-Algorithm
starts	O
from	O
the	O
J	O
point	O
(	O
termination	O
of	O
QRS	B-Algorithm
complex	I-Algorithm
and	O
the	O
beginning	O
of	O
ST	B-Algorithm
segment	I-Algorithm
)	O
and	O
ends	O
with	O
the	O
T	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
The	O
ST	B-Algorithm
segment	I-Algorithm
is	O
the	O
plateau	O
phase	O
,	O
in	O
which	O
the	O
majority	O
of	O
the	O
myocardial	O
cells	O
had	O
gone	O
through	O
depolarization	O
but	O
not	O
repolarization	O
.	O
</s>
<s>
The	O
ST	B-Algorithm
segment	I-Algorithm
is	O
the	O
isoelectric	B-Application
line	I-Application
because	O
there	O
is	O
no	O
voltage	O
difference	O
across	O
cardiac	O
muscle	O
cell	O
membrane	O
during	O
this	O
state	O
.	O
</s>
<s>
Any	O
distortion	O
in	O
the	O
shape	O
,	O
duration	O
,	O
or	O
height	O
of	O
the	O
cardiac	B-Algorithm
action	I-Algorithm
potential	I-Algorithm
can	O
distort	O
the	O
ST	B-Algorithm
segment	I-Algorithm
.	O
</s>
<s>
An	O
ST	B-Algorithm
elevation	I-Algorithm
is	O
considered	O
significant	O
if	O
the	O
vertical	O
distance	O
inside	O
the	O
ECG	B-Application
trace	O
and	O
the	O
baseline	O
at	O
a	O
point	O
0.04	O
seconds	O
after	O
the	O
J-point	O
is	O
at	O
least	O
0.1	O
mV	O
(	O
usually	O
representing	O
1	O
mm	O
or	O
1	O
small	O
square	O
)	O
in	O
a	O
limb	O
lead	O
or	O
0.2	O
mV	O
(	O
2mm	O
or	O
2	O
small	O
squares	O
)	O
in	O
a	O
precordial	O
lead	O
.	O
</s>
<s>
The	O
leads	O
facing	O
the	O
injured	O
cardiac	O
muscle	O
cells	O
will	O
record	O
the	O
action	O
potential	O
as	O
ST	B-Algorithm
elevation	I-Algorithm
during	O
systole	O
while	O
during	O
diastole	O
,	O
there	O
will	O
be	O
depression	O
of	O
the	O
PR	O
segment	O
and	O
the	O
PT	O
segment	O
.	O
</s>
<s>
Since	O
PR	O
and	O
PT	O
interval	O
are	O
regarded	O
as	O
baseline	O
,	O
ST	B-Algorithm
segment	I-Algorithm
elevation	I-Algorithm
is	O
regarded	O
as	O
a	O
sign	O
of	O
myocardial	O
ischemia	O
.	O
</s>
<s>
The	O
opposing	O
leads	O
(	O
such	O
as	O
V3	O
and	O
V4	O
versus	O
posterior	O
leads	O
V7	O
–	O
V9	O
)	O
always	O
show	O
reciprocal	O
ST	B-Algorithm
segment	I-Algorithm
changes	O
(	O
ST	B-Algorithm
elevation	I-Algorithm
in	O
one	O
lead	O
is	O
followed	O
by	O
ST	B-Algorithm
depression	I-Algorithm
in	O
the	O
opposing	O
lead	O
)	O
.	O
</s>
<s>
An	O
upsloping	O
,	O
convex	O
ST	B-Algorithm
segment	I-Algorithm
is	O
highly	O
predictive	O
of	O
a	O
myocardial	O
infarction	O
(	O
Pardee	O
sign	O
)	O
while	O
a	O
concave	O
ST	B-Algorithm
elevation	I-Algorithm
is	O
less	O
suggestive	O
and	O
can	O
be	O
found	O
in	O
other	O
non-ischaemic	O
causes	O
.	O
</s>
<s>
Following	O
infarction	O
,	O
ventricular	O
aneurysm	O
can	O
develop	O
,	O
which	O
leads	O
to	O
persistent	O
ST	B-Algorithm
elevation	I-Algorithm
,	O
loss	O
of	O
S	O
wave	O
,	O
and	O
T	B-Algorithm
wave	I-Algorithm
inversion	O
.	O
</s>
<s>
Weakening	O
of	O
the	O
electrical	O
activity	O
of	O
the	O
cardiac	O
muscles	O
causes	O
the	O
decrease	O
in	O
height	O
of	O
the	O
R	B-Algorithm
wave	I-Algorithm
in	O
those	O
leads	O
facing	O
it	O
.	O
</s>
<s>
In	O
these	O
conditions	O
,	O
there	O
will	O
mostly	O
be	O
concave	O
ST	B-Algorithm
elevations	I-Algorithm
in	O
almost	O
all	O
the	O
leads	O
except	O
for	O
aVR	O
and	O
V1	O
.	O
</s>
<s>
These	O
two	O
leads	O
,	O
ST	B-Algorithm
depression	I-Algorithm
will	O
be	O
seen	O
because	O
they	O
are	O
the	O
opposing	O
leads	O
of	O
the	O
cardiac	O
axis	O
.	O
</s>
<s>
R	B-Algorithm
wave	I-Algorithm
in	O
most	O
cases	O
will	O
be	O
unaltered	O
.	O
</s>
<s>
In	O
two	O
weeks	O
after	O
pericarditis	O
,	O
there	O
will	O
be	O
upward	O
concave	O
ST	B-Algorithm
elevation	I-Algorithm
,	O
positive	O
T	B-Algorithm
wave	I-Algorithm
,	O
and	O
PR	O
depression	O
.	O
</s>
<s>
After	O
several	O
more	O
weeks	O
,	O
PR	O
and	O
ST	B-Algorithm
segments	I-Algorithm
normalised	O
with	O
flattened	O
T	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
At	O
last	O
,	O
there	O
will	O
be	O
T	B-Algorithm
wave	I-Algorithm
inversion	O
which	O
will	O
take	O
weeks	O
or	O
months	O
to	O
vanish	O
.	O
</s>
<s>
Thus	O
,	O
ST	B-Algorithm
elevation	I-Algorithm
may	O
be	O
present	O
on	O
all	O
or	O
some	O
leads	O
of	O
ECG	B-Application
.	O
</s>
<s>
Myocardial	O
infarction	O
(	O
see	O
also	O
ECG	B-Algorithm
in	I-Algorithm
myocardial	I-Algorithm
infarction	I-Algorithm
)	O
.	O
</s>
<s>
ST	B-Algorithm
elevation	I-Algorithm
in	O
select	O
leads	O
is	O
more	O
common	O
with	O
myocardial	O
infarction	O
.	O
</s>
<s>
Acute	O
pericarditis	O
ST	B-Algorithm
elevation	I-Algorithm
in	O
all	O
leads	O
(	O
diffuse	O
ST	B-Algorithm
elevation	I-Algorithm
)	O
is	O
more	O
common	O
with	O
acute	O
pericarditis	O
.	O
</s>
