Rapid Interpretations of EKGs - Chapter 7 highlights

Question 1

Axis refers to the ________ of depolarization as it passes through the heart.

Answer 1

direction

Question 2

We can demonstrate the general direction of the movement of depolarization by using a ______.

Answer 2

vector

Question 3

Vectors can represent both _______ and _______ of depolarization.

Answer 3

direction and magnitude

Question 4

Where in the heart does ventricular depolarization begin and where does it proceed to? (review from previous chapter)

Answer 4

it begins at the endocardial lining of the ventricles and proceeds through the thickness of the ventricular wall

Question 5

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

Answer 5

“Mean QRS Vector”

Question 6

Where does the Mean QRS Vector originate from?

Answer 6

the AV node

Question 7

Depolarization is an advancing wave of _____ ions.

Answer 7

Na+

Question 8

The “axis” of the heart is simply the Mean QRS Vector when located by degrees in the _______ plane.

Answer 8

frontal plane (the normal vector points downward and to the patient’s left, that is, between 0 and +90 degrees)

Question 9

If the heart is rotated toward the patient’s right side, the Mean QRS Vector moves toward the patient’s _______ side. (common in tall, slender people) In very obese people the diaphragm is pushed up (and also the heart), so the Mean QRS Vector may point directly to the patient’s ______.

Answer 9

right side

left

Question 10

In a hypertrophied ventricle, is there an increase or decrease in depolarization?

Answer 10

increase

(so, since there is more depolarization, the Mean QRS Vector deviates more toward the ventricle that is hypertrophied)

Question 11

In myocardial infarction, the necrotic (dead) area of heart has an increase or decrease in depolarization?

Answer 11

decrease (it doesn’t depolarize at all)

(so, the unopposed vectors from the other side of the heart draw the Mean QRS Vector away from the infarct)

Question 12

Which lead is the best for determining Right Axis Deviation?

Answer 12

Lead I

Question 13

If the QRS is negative in lead I, what does this signify?

Answer 13

Right Axis Deviation

Question 14

If the QRS in the AVF lead is positive, then which way does the vector point?

Answer 14

downward

Question 15

If the QRS in Lead I is positive and the QRS in AVF is positive, what does this mean?

Answer 15

Normal Axis

(two thumbs way up!)

Question 16

If the QRS in Lead I is positive and the QRS in AVF is negative, what does this mean?

Answer 16

Left Axis Deviation

Question 17

If the QRS in Lead I is negative and the QRS in AVF is negative, what does this mean?

Answer 17

Extreme Right Axis Deviation

Question 18

When depolarization moves in a direction perpendicular to the orientation of a lead, the deflection is minimal and is called “__________”.

Answer 18

“isoelectric”

(an isoelectric QRS records equal magnitudes of upward and downward deflection)

Question 19

To locate the position of the Vector (axis) more precisely (ie. in degrees) in the frontal plane, what are the two steps?

Answer 19

1st: locate the axis quadrant
2nd: note the limb lead in which the QRS is most isolelectric

Question 20

Although the axis may “deviate” in the frontal plane, the vector is said to “______” in the horizontal plane.

Answer 20

“rotate”

Question 21

The orientation of chest lead V2 makes it the most informative lead for the determination of what?

Answer 21

both anterior and posterior infarction

Question 22

Axis ________ is in the frontal plane. Axis ________ is in the horizontal plane.

Answer 22

deviation = frontal plane

rotation = horizontal plane