Chapter 7: Axis Flashcards

1
Q

Axis refers to the _________ of the ________ of ______________.

A

direction, movement, depolarization

p. 203

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2
Q

We can demonstrate the general direction of the movement of depolarization by…

A

…using a vector.

p. 204

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3
Q

______________ of the ventricles and their ___________ is represented by the QRS complex.

A

Depolarization, contraction

p. 205

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4
Q

If we add up all the small _______ of ventricular depolarization (considering both _________ and _________), we have one large “____ ___ ______” that represents the general direction of ventricular depolarization.

A

vectors, direction, magnitude
“Mean QRS Vector”
(p. 207)

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5
Q

By convention, we consider the origin of the Mean QRS Vector to be the __ ____, so the ____ of the vector is always the __ ____.

A

AV Node, tail, AV Node

p. 207

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6
Q

Since the depolarization vectors of the thicker left ventricle are larger, the Mean QRS Vector points more toward the ____.

A

left

p. 207

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7
Q

The limb leads are used to determine the position (“____”) of the mean QRS Vector in the _______ plane.

A

Axis, frontal

p. 209

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8
Q

The Vector normally points ________ and to the patient’s ____, that is, between _ and __ degrees.

A

downward, left
0, 90
(p. 209)

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9
Q

The axis of the heart is simply the Mean QRS Vector when located by degrees in the frontal plane. Note that 0 degrees is on the patient’s ____, that the lower half of the circle is “________” degrees, and that axis is often denoted in the medical literature as “_”, as in “A = 30 degrees”, and it may be called __________ ____.

A

left, positive, A, electrical axis

p. 209

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10
Q

In obese individuals the increased __________ _______ often pushes the diaphragm upward so the position of the displaced heart may be called “__________ _____”.

A

abdominal pressure, horizontal heart

p. 210

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11
Q

With hypertrophy of one ventricle, the greater depolarization activity of the hypertrophied side displaces the Mean Vector…

A

…toward the hypertrophied side.

p. 211

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12
Q

In a myocardial infarction, there is a necrotic area of the heart that has lost its _____ ______ and does not __________. The unopposed vectors from the other side draw the Mean Vector…

A

…blood supply, depolarize.

…away from the infarct.
p. 212

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13
Q

“Axis” is the Mean QRS Vector when given in _______, and the normal axis range is _ to __ degrees in the _______ plane.

A

degrees, 0 to 90, frontal

p. 213

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14
Q

Lead I uses the left arm as the _______ electrode and the right arm as the ________ electrode.

A

positive, negative

p. 215

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15
Q

The inferior leads are ___, ___, and ___, and use the ____ ____ as the positive electrode.

A

II, III, AVF, left foot

p. 218

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16
Q

The lateral leads are ___ and ___, and use the ____ ____ as the positive electrode.

A

I and AVL, left arm

p. 218

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17
Q

The only horizontal lead is lead __ and the only vertical lead is __.

A

lead I, AVF

p. 218

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18
Q

Considering Lead I, if the QRS is mainly negative (downward), the Vector points to the patient’s ____ side.

A

right

p. 220

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19
Q

If the QRS is negative in lead I (Vector points toward patient’s right side), this is known as _____ ____ _________.

A

right axis deviation

p. 221

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20
Q

Which lead is the best for detecting right axis deviation (RAD)?

A

Lead I

p. 222

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21
Q

If the QRS complex is positive in lead I (which it _______ __), this indicates that there is no ____, because the Vector is pointing to the left side of the patient.

A

usually is
R.A.D.
(p. 222)

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22
Q

When we switch the EKG machine to monitor lead AVF, the machine makes the electrode on the ____ ____ positive. The lower half of the imaginary sphere is ________. The center of the sphere is the __ ____.
Considering lead AVF of the EKG, if the QRS is mainly positive on the tracing, then the Mean QRS Vector points ________ into the positive half of the sphere, toward the positive (lead AVF) electrode.

A
left foot
positive
AV Node
downward
(p. 223)
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23
Q

If the QRS is positive in lead I and also positive in AVF, the Vector points _________ and to the patient’s ____. This is the ______ axis range.

A

downward, left
normal
(p. 227)

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24
Q

If the Vector points upward (from the AV Node) and to the patient’s left, this is ____ ____ _________.

A

left axis deviation

p. 228

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25
Q

If the Vector points to the patient’s right side, this is _____ ____ _________.

A

right axis deviation

p. 228

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26
Q

If the QRS is positive in Lead I, and negative in AVF, that places the Vector in the _____ _____ quadrant. This is _____ ____ deviation.

A

upper left
left axis
(p. 230)

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27
Q

Any time the QRS complex is negative in lead I…

A

…there is right axis deviation.

p. 231

28
Q

Any time the QRS complex is positive in lead I and negative in lead AVF…

A

…there is left axis deviation.

p. 231

29
Q

When depolarization moves in a direction perpendicular to the orientation of a lead, the deflection is…

A

…minimal and/or isoelectric.

p. 232

30
Q

To locate the position of the Vector (Axis) more precisely, in degrees in the frontal plane: first locate the ____ ________, and then note the ____ ____ in which the QRS is most isoelectric.

A

axis quadrant
limb lead
(p. 233)

31
Q

A patient with left axis deviation has a Vector between _ and __ degrees.

A

0 and -90 degrees

p. 233

32
Q

A patient with left axis deviation, and an isoelectric QRS in lead I has an electrical axis of…

A

… -90 degrees

p. 233

33
Q

A patient with left axis deviation, and an isoelectric QRS in lead AVR has an electrical axis of…

A

… -60 degrees

p. 233

34
Q

A patient with left axis deviation, and an isoelectric QRS in lead II has an electrical axis of…

A

… -30 degrees

p. 233

35
Q

A patient with left axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…

A

… 0 degrees

p. 233

36
Q

A patient with an axis deviation in the normal range, and an isoelectric QRS in lead AVF has an electrical axis of…

A

… 0 degrees

p. 233

37
Q

A patient with an axis deviation in the normal range, and an isoelectric QRS in lead III has an electrical axis of…

A

… +30 degrees

p. 233

38
Q

A patient with an axis deviation in the normal range, and an isoelectric QRS in lead AVL has an electrical axis of…

A

… +60 degrees

p. 233

39
Q

A patient with an axis deviation in the normal range, and an isoelectric QRS in lead I has an electrical axis of…

A

… +90 degrees

p. 233

40
Q

The Axis is about 90 degrees from the orientation of the…

A

…most isoelectric lead.

p. 232

41
Q

A patient with extreme right axis deviation, and an isoelectric QRS in lead I has an electrical axis of…

A

… -90 degrees

p. 234

42
Q

A patient with extreme right axis deviation, and an isoelectric QRS in lead AVL has an electrical axis of…

A

… -120 degrees

p. 234

43
Q

A patient with extreme right axis deviation, and an isoelectric QRS in lead III has an electrical axis of…

A

… -150 degrees

p. 234

44
Q

A patient with extreme right axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…

A

… -180 degrees

p. 234

45
Q

A patient with right axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…

A

… +180 degrees

p. 234

46
Q

A patient with right axis deviation, and an isoelectric QRS in lead II has an electrical axis of…

A

… +150 degrees

p. 234

47
Q

A patient with right axis deviation, and an isoelectric QRS in lead AVR has an electrical axis of…

A

… +120 degrees

p. 234

48
Q

A patient with right axis deviation, and an isoelectric QRS in lead I has an electrical axis of…

A

… +90 degrees

p. 234

49
Q

A patient with an axis of 0 to +90 degrees has a…

A

…normal axis.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

50
Q

A patient with an axis of +91 to + or - 180 degrees has a…

A

…right axis deviation.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

51
Q

A patient with an axis of -1 to -30 degrees may have a…

A

…physiologic left axis deviation.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

52
Q

A patient with an axis of -31 to -90 degrees has a…

A

…pathologic left axis deviation.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

53
Q

A patient with an axis of -91 to + or -180 degrees has an…

A

…extreme right axis deviation, or an indeterminate axis.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

54
Q

Determining the Axis:
Step 1 – Look at Lead I
a.) Count the # of mm of positive deflection of the QRS complex.
b.) Count the number of mm of negative deflection of the QRS complex.
c.) Subtract the negative deflection # from the positive deflection #. This number is the ___ _______ # for Lead I.
Step 2 – Repeat the process for Lead AVF.
Step 3 – Draw a perpendicular line through Lead I on the hexaxial reference plane at the spot marked.
Step 4 – Draw a perpendicular line through Lead AVF at the spot marked.
Step 5 – Connect the intersection of these 2 lines with the central terminal. This final line points to the number of degrees.

A

NET VECTOR

55
Q

Remember that an electrical axis of 0 degrees is actually considered…

A

…normal.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

56
Q

Determining the axis via the “easier method”:
Look at Lead I and Lead AVF.
If the QRS’s are both pointing up, the patient has a…

A

…normal axis.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

57
Q

If the QRS’s are pointing together (meaning lead 1 points down and AVF points up).
(Remember: right together, left apart.)

A

…there is right axis deviation.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

58
Q

If the QRS’s are pointing apart (meaning lead I points up and AVF points down)…
(Remember: right together, left apart.)

A

…there is left axis deviation.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

59
Q

If both QRS’s are pointing down…

A

…there is extreme right axis deviation (a. k. a. an indeterminate axis).
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)

60
Q

A left axis deviation is normal in…

A

…older people, obese people, and pregnant women.

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

61
Q

What disease processes often cause left axis deviation?

A

Emphysema
Left ventricular hypertrophy
Left anterior fascicular block
Inferior wall MI
LBBB
Ventricular tachycardias (but can cause all kinds of axis deviations)
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)

62
Q

What disease processes often cause right axis deviation?

A
Emphysema
COPD
Right ventricular hypertrophy
RBBB
Left posterior fascicular block
Ventricular tachycardias
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)
63
Q

What disease processes often cause indeterminate (extreme right) axis deviation?

A

Ventricular tachycardias
Bifascicular block
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)

64
Q

When an EKG is interpreting R-wave progression, which leads is it most likely using?

A

The precordial leads

YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0

65
Q

If left axis deviation is present, examine lead __ to determine if this deviation is pathologic. If the QRS in lead __ is predominantly ________, the LAD is non-pathologic, if it is predominately ________, it is pathologic.

A

II
II
positive
negative