Biomedical Engineering Reference
In-Depth Information
(
∀
l
1
,k
1
·
l
1
∈
LEADS
∧
k
1
∈
LEADS
∧
((ST
_
elevation(l
1
)
=
FA L S E
∨
ST
_
elevation(k
1
)
=
FA L S E )
((ST
_
seg
_
ele(l
1
)<
1000
∨
ST
_
seg
_
ele(k
1
)<
1000
)
(Abnormal
_
Shaped
_
ST(l
1
)
∨
Abnormal
_
Shaped
_
ST(k
1
)
=
FA L S E )))
⇒
l
1
=
k
1
))
grd2
:∀
l
·
l
∈
LEADS
⇒
T
_
inversion(l) >
5000
grd3
:∀
l
·
l
∈
LEADS
⇒
T
_
inversion
_
l
_
d(l)
=
Diffuse
grd4
:
T
_
Normal
_
Status
=
FA L S E
THEN
act1
:
Disease
_
step
8_
B
:∈ {
Cardiomyopathy, other
_
nonspecific
}
END
=
FA L S E
10.5.9 Eighth Refinement: Assess Electrical Axis
After finding all kinds of information about abnormal ECG, it is also essential to
check the electrical axis (see Table
10.1
) using two simple clues:
•
If leads I and aVF are upright; the axis is normal.
•
The axis is perpendicular to the lead with the most equiphasic or smallest QRS
deflection. Left-axis deviation and the commonly associated left anterior fascicu-
lar block are visible in ECG signal.
This refinement is very essential refinement for the ECG interpretation because
of the different angle of the ECG signal gives different output and angle based pre-
diction can be changed [
16
]. So, for accuracy of the ECG interpretation electri-
cal axis must be included. New variables
minAngle
,
maxAngle
,
Axis_Devi
and
Dis-
Table 10.1
Electrical axis
Most equiphasic lead
Lead perpendicular
Axis
Lead I and aVF positive
=
normal axis
III
aVR
Normal
=+
30 degrees
aVL
II
Normal
60 degrees
Lead I positive and aVF negative
=+
=
Left axis
II
aVL (QRS positive)
Left
=−
30 degrees
aVR
III (QRS negative)
Left
=−
60 degrees
I
aVF (QRS negative)
Left
90 degrees
Lead I negative and aVF positive
=−
=
right axis
aVR
III (QRS positive)
Right
=+
120 degrees
II
aVL (QRS negative)
Right
=+
150 degrees
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