Rapid Interpretations of EKGs - Chapter 7 highlights Flashcards
Axis
Axis refers to the ________ of depolarization as it passes through the heart.
direction
We can demonstrate the general direction of the movement of depolarization by using a ______.
vector
Vectors can represent both _______ and _______ of depolarization.
direction and magnitude
Where in the heart does ventricular depolarization begin and where does it proceed to? (review from previous chapter)
it begins at the endocardial lining of the ventricles and proceeds through the thickness of the ventricular wall
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.
“Mean QRS Vector”
Where does the Mean QRS Vector originate from?
the AV node
Depolarization is an advancing wave of _____ ions.
Na+
The “axis” of the heart is simply the Mean QRS Vector when located by degrees in the _______ plane.
frontal plane (the normal vector points downward and to the patient’s left, that is, between 0 and +90 degrees)
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 ______.
right side
left
In a hypertrophied ventricle, is there an increase or decrease in depolarization?
increase
(so, since there is more depolarization, the Mean QRS Vector deviates more toward the ventricle that is hypertrophied)
In myocardial infarction, the necrotic (dead) area of heart has an increase or decrease in depolarization?
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)
Which lead is the best for determining Right Axis Deviation?
Lead I
If the QRS is negative in lead I, what does this signify?
Right Axis Deviation
If the QRS in the AVF lead is positive, then which way does the vector point?
downward
If the QRS in Lead I is positive and the QRS in AVF is positive, what does this mean?
Normal Axis
(two thumbs way up!)