Chapter 7: Axis Flashcards
Axis refers to the _________ of the ________ of ______________.
direction, movement, depolarization
p. 203
We can demonstrate the general direction of the movement of depolarization by…
…using a vector.
p. 204
______________ of the ventricles and their ___________ is represented by the QRS complex.
Depolarization, contraction
p. 205
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.
vectors, direction, magnitude
“Mean QRS Vector”
(p. 207)
By convention, we consider the origin of the Mean QRS Vector to be the __ ____, so the ____ of the vector is always the __ ____.
AV Node, tail, AV Node
p. 207
Since the depolarization vectors of the thicker left ventricle are larger, the Mean QRS Vector points more toward the ____.
left
p. 207
The limb leads are used to determine the position (“____”) of the mean QRS Vector in the _______ plane.
Axis, frontal
p. 209
The Vector normally points ________ and to the patient’s ____, that is, between _ and __ degrees.
downward, left
0, 90
(p. 209)
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 __________ ____.
left, positive, A, electrical axis
p. 209
In obese individuals the increased __________ _______ often pushes the diaphragm upward so the position of the displaced heart may be called “__________ _____”.
abdominal pressure, horizontal heart
p. 210
With hypertrophy of one ventricle, the greater depolarization activity of the hypertrophied side displaces the Mean Vector…
…toward the hypertrophied side.
p. 211
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…
…blood supply, depolarize.
…away from the infarct.
p. 212
“Axis” is the Mean QRS Vector when given in _______, and the normal axis range is _ to __ degrees in the _______ plane.
degrees, 0 to 90, frontal
p. 213
Lead I uses the left arm as the _______ electrode and the right arm as the ________ electrode.
positive, negative
p. 215
The inferior leads are ___, ___, and ___, and use the ____ ____ as the positive electrode.
II, III, AVF, left foot
p. 218
The lateral leads are ___ and ___, and use the ____ ____ as the positive electrode.
I and AVL, left arm
p. 218
The only horizontal lead is lead __ and the only vertical lead is __.
lead I, AVF
p. 218
Considering Lead I, if the QRS is mainly negative (downward), the Vector points to the patient’s ____ side.
right
p. 220
If the QRS is negative in lead I (Vector points toward patient’s right side), this is known as _____ ____ _________.
right axis deviation
p. 221
Which lead is the best for detecting right axis deviation (RAD)?
Lead I
p. 222
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.
usually is
R.A.D.
(p. 222)
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.
left foot positive AV Node downward (p. 223)
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.
downward, left
normal
(p. 227)
If the Vector points upward (from the AV Node) and to the patient’s left, this is ____ ____ _________.
left axis deviation
p. 228
If the Vector points to the patient’s right side, this is _____ ____ _________.
right axis deviation
p. 228
If the QRS is positive in Lead I, and negative in AVF, that places the Vector in the _____ _____ quadrant. This is _____ ____ deviation.
upper left
left axis
(p. 230)
Any time the QRS complex is negative in lead I…
…there is right axis deviation.
p. 231
Any time the QRS complex is positive in lead I and negative in lead AVF…
…there is left axis deviation.
p. 231
When depolarization moves in a direction perpendicular to the orientation of a lead, the deflection is…
…minimal and/or isoelectric.
p. 232
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.
axis quadrant
limb lead
(p. 233)
A patient with left axis deviation has a Vector between _ and __ degrees.
0 and -90 degrees
p. 233
A patient with left axis deviation, and an isoelectric QRS in lead I has an electrical axis of…
… -90 degrees
p. 233
A patient with left axis deviation, and an isoelectric QRS in lead AVR has an electrical axis of…
… -60 degrees
p. 233
A patient with left axis deviation, and an isoelectric QRS in lead II has an electrical axis of…
… -30 degrees
p. 233
A patient with left axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…
… 0 degrees
p. 233
A patient with an axis deviation in the normal range, and an isoelectric QRS in lead AVF has an electrical axis of…
… 0 degrees
p. 233
A patient with an axis deviation in the normal range, and an isoelectric QRS in lead III has an electrical axis of…
… +30 degrees
p. 233
A patient with an axis deviation in the normal range, and an isoelectric QRS in lead AVL has an electrical axis of…
… +60 degrees
p. 233
A patient with an axis deviation in the normal range, and an isoelectric QRS in lead I has an electrical axis of…
… +90 degrees
p. 233
The Axis is about 90 degrees from the orientation of the…
…most isoelectric lead.
p. 232
A patient with extreme right axis deviation, and an isoelectric QRS in lead I has an electrical axis of…
… -90 degrees
p. 234
A patient with extreme right axis deviation, and an isoelectric QRS in lead AVL has an electrical axis of…
… -120 degrees
p. 234
A patient with extreme right axis deviation, and an isoelectric QRS in lead III has an electrical axis of…
… -150 degrees
p. 234
A patient with extreme right axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…
… -180 degrees
p. 234
A patient with right axis deviation, and an isoelectric QRS in lead AVF has an electrical axis of…
… +180 degrees
p. 234
A patient with right axis deviation, and an isoelectric QRS in lead II has an electrical axis of…
… +150 degrees
p. 234
A patient with right axis deviation, and an isoelectric QRS in lead AVR has an electrical axis of…
… +120 degrees
p. 234
A patient with right axis deviation, and an isoelectric QRS in lead I has an electrical axis of…
… +90 degrees
p. 234
A patient with an axis of 0 to +90 degrees has a…
…normal axis.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
A patient with an axis of +91 to + or - 180 degrees has a…
…right axis deviation.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
A patient with an axis of -1 to -30 degrees may have a…
…physiologic left axis deviation.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
A patient with an axis of -31 to -90 degrees has a…
…pathologic left axis deviation.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
A patient with an axis of -91 to + or -180 degrees has an…
…extreme right axis deviation, or an indeterminate axis.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
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.
NET VECTOR
Remember that an electrical axis of 0 degrees is actually considered…
…normal.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
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…
…normal axis.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
If the QRS’s are pointing together (meaning lead 1 points down and AVF points up).
(Remember: right together, left apart.)
…there is right axis deviation.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
If the QRS’s are pointing apart (meaning lead I points up and AVF points down)…
(Remember: right together, left apart.)
…there is left axis deviation.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
If both QRS’s are pointing down…
…there is extreme right axis deviation (a. k. a. an indeterminate axis).
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)
A left axis deviation is normal in…
…older people, obese people, and pregnant women.
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
What disease processes often cause left axis deviation?
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)
What disease processes often cause right axis deviation?
Emphysema COPD Right ventricular hypertrophy RBBB Left posterior fascicular block Ventricular tachycardias (YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)
What disease processes often cause indeterminate (extreme right) axis deviation?
Ventricular tachycardias
Bifascicular block
(YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0)
When an EKG is interpreting R-wave progression, which leads is it most likely using?
The precordial leads
YouTube video: https://www.youtube.com/watch?v=Mu71NqijEu0
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.
II
II
positive
negative
