<s>
The	O
'	O
U	O
 '	O
wave	O
is	O
a	O
wave	O
on	O
an	O
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
.	O
</s>
<s>
It	O
comes	O
after	O
the	O
T	B-Algorithm
wave	I-Algorithm
of	O
ventricular	B-Application
repolarization	I-Application
and	O
may	O
not	O
always	O
be	O
observed	O
as	O
a	O
result	O
of	O
its	O
small	O
size	O
.	O
</s>
<s>
'	O
U	O
 '	O
waves	O
are	O
thought	O
to	O
represent	O
repolarization	O
of	O
the	O
Purkinje	B-Algorithm
fibers	I-Algorithm
.	O
</s>
<s>
However	O
,	O
the	O
exact	O
source	O
of	O
the	O
U	B-Algorithm
wave	I-Algorithm
remains	O
unclear	O
.	O
</s>
<s>
"	O
The	O
U	B-Algorithm
wave	I-Algorithm
is	O
the	O
momentum	O
carried	O
by	O
the	O
blood	O
in	O
the	O
coronary	O
arteries	O
and	O
blood	O
vessels	O
"	O
.	O
</s>
<s>
The	O
U	B-Algorithm
wave	I-Algorithm
is	O
the	O
momentum	O
carried	O
by	O
the	O
blood	O
in	O
the	O
coronary	O
arteries	O
and	O
blood	O
vessels	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
take	O
this	O
momentum	O
back	O
to	O
Purkinje	B-Algorithm
fibers	I-Algorithm
along	O
the	O
vessels	O
of	O
the	O
myocardium	O
.	O
</s>
<s>
This	O
idea	O
is	O
also	O
proved	O
by	O
the	O
fact	O
that	O
hypertrophy	O
of	O
the	O
left	O
ventricle	O
,	O
myocardial	O
ischemia	O
,	O
coronary	O
and	O
insufficiency	O
have	O
momentum	O
there	O
is	O
no	O
possibility	O
to	O
move	O
to	O
the	O
Purkinje	B-Algorithm
fibers	I-Algorithm
,	O
therefore	O
,	O
the	O
ECG	B-Application
recorded	O
a	O
negative	O
U	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
According	O
to	O
many	O
studies	O
,	O
U	B-Algorithm
waves	I-Algorithm
often	O
register	O
in	O
all	O
leads	O
except	O
V6	O
,	O
most	O
frequently	O
in	O
V2	O
and	O
V3	O
when	O
the	O
heart	O
rate	O
is	O
greater	O
than	O
96	O
beats	O
per	O
minute	O
.	O
</s>
<s>
Particularly	O
difficult	O
is	O
the	O
allocation	O
of	O
the	O
boundaries	O
of	O
the	O
U	B-Algorithm
wave	I-Algorithm
on	O
the	O
background	O
of	O
the	O
T	B-Algorithm
wave	I-Algorithm
and	O
R	B-Algorithm
wave	I-Algorithm
,	O
which	O
may	O
partial	O
or	O
complete	O
(	O
in	O
the	O
case	O
of	O
T	B-Algorithm
wave	I-Algorithm
)	O
the	O
merger	O
.	O
</s>
<s>
Higher	O
values	O
of	O
heart	O
rate	O
or	O
hypocalcemia	O
U	B-Algorithm
wave	I-Algorithm
are	O
superimposed	O
on	O
the	O
T	B-Algorithm
wave	I-Algorithm
and	O
in	O
tachycardia	B-Application
—	O
merges	O
with	O
the	O
R-wave	B-Algorithm
of	O
the	O
next	O
cardiac	O
cycle	O
.	O
</s>
<s>
Prominent	O
U	B-Algorithm
waves	I-Algorithm
(	O
U	B-Algorithm
waves	I-Algorithm
are	O
described	O
as	O
prominent	O
if	O
they	O
are	O
more	O
than	O
1-2	O
mm	O
or	O
25%	O
of	O
the	O
height	O
of	O
the	O
T	B-Algorithm
wave	I-Algorithm
.	O
)	O
</s>
<s>
are	O
most	O
often	O
seen	O
in	O
hypokalemia	O
but	O
may	O
be	O
present	O
in	O
hypercalcemia	O
,	O
thyrotoxicosis	O
,	O
or	O
exposure	O
to	O
digitalis	O
,	O
epinephrine	O
and	O
Class	O
1A	O
and	O
3	O
antiarrhythmics	B-Algorithm
,	O
as	O
well	O
as	O
in	O
congenital	O
long	O
QT	O
syndrome	O
,	O
and	O
in	O
the	O
setting	O
of	O
intracranial	O
hemorrhage	O
.	O
</s>
<s>
An	O
inverted	O
U	B-Algorithm
wave	I-Algorithm
may	O
represent	O
myocardial	O
ischemia	O
(	O
and	O
especially	O
appears	O
to	O
have	O
a	O
high	O
positive	O
predictive	O
accuracy	O
for	O
left	O
anterior	O
descending	O
coronary	O
artery	O
disease	O
)	O
or	O
left	O
ventricular	O
volume	O
overload	O
.	O
</s>
