<s>
The	O
QRS	B-Algorithm
complex	I-Algorithm
is	O
the	O
combination	O
of	O
three	O
of	O
the	O
graphical	O
deflections	O
seen	O
on	O
a	O
typical	O
electrocardiogram	B-Application
(	O
ECG	B-Application
or	O
EKG	B-Application
)	O
.	O
</s>
<s>
In	O
adults	O
,	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
normally	O
lasts	O
;	O
in	O
children	O
it	O
may	O
be	O
shorter	O
.	O
</s>
<s>
A	O
Q	O
wave	O
is	O
any	O
downward	O
deflection	O
immediately	O
following	O
the	O
P	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
An	O
R	B-Algorithm
wave	I-Algorithm
follows	O
as	O
an	O
upward	O
deflection	O
,	O
and	O
the	O
S	O
wave	O
is	O
any	O
downward	O
deflection	O
after	O
the	O
R	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
The	O
T	B-Algorithm
wave	I-Algorithm
follows	O
the	O
S	O
wave	O
,	O
and	O
in	O
some	O
cases	O
,	O
an	O
additional	O
U	B-Algorithm
wave	I-Algorithm
follows	O
the	O
T	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
To	O
measure	O
the	O
QRS	B-Algorithm
interval	O
start	O
at	O
the	O
end	O
of	O
the	O
PR	O
interval	O
(	O
or	O
beginning	O
of	O
the	O
Q	O
wave	O
)	O
to	O
the	O
end	O
of	O
the	O
S	O
wave	O
.	O
</s>
<s>
When	O
the	O
duration	O
is	O
longer	O
it	O
is	O
considered	O
a	O
wide	O
QRS	B-Algorithm
complex	I-Algorithm
.	O
</s>
<s>
Depolarization	O
of	O
the	O
heart	O
ventricles	O
occurs	O
almost	O
simultaneously	O
,	O
via	O
the	O
bundle	B-Algorithm
of	I-Algorithm
His	I-Algorithm
and	O
Purkinje	B-Algorithm
fibers	I-Algorithm
.	O
</s>
<s>
If	O
they	O
are	O
working	O
efficiently	O
,	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
duration	O
in	O
adults	O
is	O
.	O
</s>
<s>
Any	O
abnormality	O
of	O
conduction	O
takes	O
longer	O
and	O
causes	O
"	O
widened	O
"	O
QRS	B-Algorithm
complexes	I-Algorithm
.	O
</s>
<s>
In	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
,	O
there	O
can	O
be	O
an	O
abnormal	O
second	O
upward	O
deflection	O
within	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
.	O
</s>
<s>
Therefore	O
,	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
is	O
considerably	O
larger	O
than	O
the	O
P	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
The	O
QRS	B-Algorithm
complex	I-Algorithm
is	O
often	O
used	O
to	O
determine	O
the	O
axis	O
of	O
the	O
electrocardiogram	B-Application
,	O
although	O
it	O
is	O
also	O
possible	O
to	O
determine	O
a	O
separate	O
P	B-Algorithm
wave	I-Algorithm
axis	O
.	O
</s>
<s>
The	O
duration	O
,	O
amplitude	O
,	O
and	O
morphology	O
of	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
are	O
useful	O
in	O
diagnosing	O
cardiac	B-Application
arrhythmias	I-Application
,	O
conduction	B-Application
abnormalities	I-Application
,	O
ventricular	O
hypertrophy	O
,	O
myocardial	O
infarction	O
,	O
electrolyte	O
derangements	O
,	O
and	O
other	O
disease	O
states	O
.	O
</s>
<s>
High	O
frequency	O
analysis	O
of	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
may	O
be	O
useful	O
for	O
detection	O
of	O
coronary	O
artery	O
disease	O
during	O
an	O
exercise	O
stress	O
test	O
.	O
</s>
<s>
Parameter	O
Normal	O
value	O
Value	O
comments	O
Clinical	O
significance	O
QRS	B-Algorithm
duration	O
75	O
to	O
105ms	O
Shorter	O
in	O
childrenCompendium	O
for	O
interpretation	O
of	O
ECG	B-Application
at	O
Uppsala	O
Institution	O
for	O
Clinical	O
Physiology	O
.	O
</s>
<s>
Year	O
2010	O
Prolonged	O
duration	O
could	O
indicate	O
hyperkalemia	O
or	O
intraventricular	B-Algorithm
conduction	I-Algorithm
delay	I-Algorithm
such	O
as	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
.	O
</s>
<s>
in	O
V1	O
Measured	O
in	O
increased	O
QRS	B-Algorithm
amplitude	O
Q	O
wave	O
Duration	O
up	O
to	O
40ms	O
in	O
leads	O
other	O
than	O
III	O
and	O
aVRLoyola	O
University	O
Chicago	O
Stritch	O
School	O
of	O
Medicine	O
.	O
</s>
<s>
A	O
pathologic	O
Q	O
wave	O
is	O
defined	O
as	O
having	O
a	O
deflection	O
amplitude	O
of	O
25%	O
or	O
more	O
of	O
the	O
subsequent	O
R	B-Algorithm
wave	I-Algorithm
,	O
or	O
being	O
(	O
40ms	O
)	O
in	O
width	O
and	O
in	O
amplitude	O
.	O
</s>
<s>
Looking	O
at	O
the	O
precordial	O
leads	O
,	O
the	O
R	B-Algorithm
wave	I-Algorithm
usually	O
progresses	O
from	O
showing	O
an	O
rS-type	O
complex	O
in	O
V1	O
with	O
an	O
increasing	O
R	O
and	O
a	O
decreasing	O
S	O
wave	O
when	O
moving	O
toward	O
the	O
left	O
side	O
.	O
</s>
<s>
There	O
is	O
usually	O
a	O
qR-type	O
of	O
complex	O
in	O
V5	O
and	O
V6	O
,	O
with	O
the	O
R-wave	B-Algorithm
amplitude	O
usually	O
taller	O
in	O
V5	O
than	O
in	O
V6	O
.	O
</s>
<s>
It	O
is	O
normal	O
to	O
have	O
a	O
narrow	O
QS	O
and	O
rSr	O
 '	O
patterns	O
in	O
V1	O
,	O
and	O
this	O
is	O
also	O
the	O
case	O
for	O
qRs	B-Algorithm
and	O
R	O
patterns	O
in	O
V5	O
and	O
V6	O
.	O
</s>
<s>
The	O
transition	O
zone	O
is	O
where	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
changes	O
from	O
predominantly	O
negative	O
to	O
predominantly	O
positive	O
(	O
R/S	O
ratio	O
becoming	O
>1	O
)	O
,	O
and	O
this	O
usually	O
occurs	O
at	O
V3	O
or	O
V4	O
.	O
</s>
<s>
In	O
biomedical	O
engineering	O
,	O
the	O
maximum	O
amplitude	O
in	O
the	O
R	B-Algorithm
wave	I-Algorithm
is	O
usually	O
called	O
"	O
R	O
peak	O
amplitude	O
"	O
,	O
or	O
just	O
"	O
R	O
peak	O
"	O
.	O
</s>
<s>
Accurate	O
R	O
peak	O
detection	O
is	O
essential	O
in	O
signal	O
processing	O
equipment	O
for	O
heart	O
rate	O
measurement	O
and	O
it	O
is	O
the	O
main	O
feature	O
used	O
for	O
arrhythmia	B-Application
detection	O
.	O
</s>
<s>
The	O
definition	O
of	O
poor	O
R	B-Algorithm
wave	I-Algorithm
progression	O
(	O
PRWP	O
)	O
varies	O
in	O
the	O
literature	O
.	O
</s>
<s>
It	O
may	O
be	O
defined	O
,	O
for	O
example	O
,	O
as	O
R	B-Algorithm
wave	I-Algorithm
of	O
less	O
than	O
2	O
–	O
4mm	O
in	O
leads	O
V3	O
or	O
V4	O
and/or	O
presence	O
of	O
a	O
reversed	O
R	B-Algorithm
wave	I-Algorithm
progression	O
,	O
which	O
is	O
defined	O
as	O
R	O
in	O
V4	O
<	O
R	O
in	O
V3	O
or	O
R	O
in	O
V3	O
<	O
R	O
in	O
V2	O
or	O
R	O
in	O
V2	O
<	O
R	O
in	O
V1	O
,	O
or	O
any	O
combination	O
of	O
these	O
.	O
</s>
<s>
Poor	O
R	B-Algorithm
wave	I-Algorithm
progression	O
is	O
commonly	O
attributed	O
to	O
anterior	O
myocardial	O
infarction	O
,	O
but	O
it	O
may	O
also	O
be	O
caused	O
by	O
left	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
,	O
Wolff	O
–	O
Parkinson	O
–	O
White	O
syndrome	O
,	O
right	O
and	O
left	O
ventricular	O
hypertrophy	O
,	O
or	O
a	O
faulty	O
ECG	B-Application
recording	O
technique	O
.	O
</s>
<s>
R	B-Algorithm
wave	I-Algorithm
peak	O
time	O
(	O
RWPT	O
)	O
represents	O
the	O
time	O
from	O
the	O
onset	O
of	O
QRS	B-Algorithm
complex	I-Algorithm
to	O
the	O
peak	O
of	O
R	B-Algorithm
wave	I-Algorithm
,	O
which	O
is	O
usually	O
measured	O
in	O
aVL	O
and	O
V5	O
or	O
V6	O
leads	O
.	O
</s>
<s>
R-peak	O
time	O
for	O
right	O
ventricle	O
is	O
measured	O
from	O
leads	O
V1	O
or	O
V2	O
,	O
where	O
upper	O
range	O
of	O
normal	O
is	O
35	O
ms.	O
R	B-Algorithm
wave	I-Algorithm
peak	O
time	O
for	O
left	O
ventricle	O
is	O
measured	O
from	O
lead	O
V5	O
or	O
V6	O
and	O
45	O
ms	O
is	O
the	O
upper	O
range	O
of	O
normal	O
.	O
</s>
<s>
R	B-Algorithm
wave	I-Algorithm
peak	O
time	O
is	O
considered	O
to	O
be	O
prolonged	O
if	O
it	O
's	O
more	O
than	O
45	O
ms.	O
</s>
<s>
The	O
point	O
where	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
meets	O
the	O
ST	B-Algorithm
segment	I-Algorithm
is	O
the	O
J-point	O
.	O
</s>
<s>
The	O
J-point	O
is	O
easy	O
to	O
identify	O
when	O
the	O
ST	B-Algorithm
segment	I-Algorithm
is	O
horizontal	O
and	O
forms	O
a	O
sharp	O
angle	O
with	O
the	O
last	O
part	O
of	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
.	O
</s>
<s>
However	O
,	O
when	O
the	O
ST	B-Algorithm
segment	I-Algorithm
is	O
sloped	O
or	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
is	O
wide	O
,	O
the	O
two	O
features	O
do	O
not	O
form	O
a	O
sharp	O
angle	O
and	O
the	O
location	O
of	O
the	O
J-point	O
is	O
less	O
clear	O
.	O
</s>
<s>
Not	O
every	O
QRS	B-Algorithm
complex	I-Algorithm
contains	O
a	O
Q	O
wave	O
,	O
an	O
R	B-Algorithm
wave	I-Algorithm
,	O
and	O
an	O
S	O
wave	O
.	O
</s>
<s>
By	O
convention	O
,	O
any	O
combination	O
of	O
these	O
waves	O
can	O
be	O
referred	O
to	O
as	O
a	O
QRS	B-Algorithm
complex	I-Algorithm
.	O
</s>
<s>
However	O
,	O
correct	O
interpretation	O
of	O
difficult	O
ECGs	B-Application
requires	O
exact	O
labeling	O
of	O
the	O
various	O
waves	O
.	O
</s>
<s>
If	O
both	O
complexes	O
were	O
labeled	O
RS	O
,	O
it	O
would	O
be	O
impossible	O
to	O
appreciate	O
this	O
distinction	O
without	O
viewing	O
the	O
actual	O
ECG	B-Application
.	O
</s>
<s>
Monomorphic	O
refers	O
to	O
all	O
QRS	B-Algorithm
waves	I-Algorithm
in	O
a	O
single	O
lead	O
being	O
similar	O
in	O
shape	O
.	O
</s>
<s>
Polymorphic	O
means	O
that	O
the	O
QRS	B-Algorithm
change	O
from	O
complex	O
to	O
complex	O
.	O
</s>
<s>
These	O
terms	O
are	O
used	O
in	O
the	O
description	O
of	O
ventricular	B-Application
tachycardia	I-Application
.	O
</s>
<s>
A	O
common	O
algorithm	O
used	O
for	O
QRS	B-Algorithm
complex	I-Algorithm
detection	O
is	O
the	O
Pan-Tompkins	B-Algorithm
algorithm	I-Algorithm
(	O
or	O
method	O
)	O
;	O
another	O
is	O
based	O
on	O
the	O
Hilbert	B-Algorithm
transform	I-Algorithm
.	O
</s>
