Pre-Excitation Syndrome And Axis

Question 1

What is Wolff-Parkinson-White Syndrome? (WPW)

Answer 1

1. An abnormal, accessory AV conduction pathway
   *bundle of Kent will prematurely depolarize a portion of the ventricles

Question 2

What does WPW syndrome cause?

Answer 2

1. A delta wave on EKG
2. Upsloping at the beginning of the QRS complex

Question 3

What does the delta wave create on the EKG?

Answer 3

1. Shortened PR interval
2. Lengthened QRS complex

Question 4

What are the identifying EKG characteristics of WPW Syndrome?

Answer 4

1. Shortened PR interval (<0.12)
2. P wave is sinus
3. Wide QRS complex (>0.11)
4. Presence of a delta wave

Question 5

People with WPW syndrome are predispose to what?

Answer 5

1. Paroxysmal Tachycardia

Question 6

What are the mechanisms that WPW can cause paroxysmal tachycardia?

Answer 6

1. Rapid conduction
   *Supraventricular tachycardia
2. Kent bundles that contain automaticity foci can initiate an paroxysmal tachycardia
3. Re-entry

Question 7

What is Lown-Ganong-Levine (LGL) syndrome?

Answer 7

1. James bundle (which is an extension of the anterior internodal tract)
   *There will be conduction of the atrial depolarizations directly to the Bundle of His without delay

Question 8

What are some characteristics of LGL syndrome?

Answer 8

1. No significant PR interval delay
2. P waves are adjacent to the QRS complex

Question 9

What does axis refer to?

Answer 9

1. The direction of depolarization as it passes through the heart

Question 10

What is vector?

Answer 10

1. The direction in which depolarization is moving
   *the average direction of all of the positive charges as they travel through the myocardium

Question 11

What is the direction of the mean vector called?

Answer 11

The mean electrical axis

Question 12

Where is the average vector?

Answer 12

1. Towards the left
   *since the left ventricles is thicker, its vectors are bigger

Question 13

What is the normal mean electrical axis?

Answer 13

1. Between 0 to 90 degrees

Question 14

How does axis and hypertrophy relate to each other?

Answer 14

1. The larger ventricle would alter the axis

Question 15

What is the normal deflection in lead aVR?

Answer 15

Downward

Question 16

What is the normal deflection in lead aVL?

Answer 16

Upward

Question 17

What is the normal deflection in lead aVF?

Answer 17

Upward

Question 18

What is the angle of orientation of lead I

Answer 18

1. 0 degrees
   *Lead or is right arm (-) to left arm (+)

Question 19

What is the angle of orientation of lead II?

Answer 19

1. +60 degrees
   *Right arm (-) to left leg (+)

Question 20

What is the angle of orientation of lead III?

Answer 20

1. +120 degrees
   *Left arm (-) to left leg (+)

Question 21

What is the angle of orientation of aVR?

Answer 21

1. -150 degrees
   *Right arm (+) and other limbs (-)

Question 22

What is the angle of orientation of aVL?

Answer 22

1. -30 degrees
   *Left arm (+) and other limbs (-)

Question 23

What is the angle of orientation of aVF?

Answer 23

1. +90 degrees
   *Left leg (+) and other limbs (-)

Question 24

What are the anterior leads?

Answer 24

1. V1 and V2
   *Over right ventricle
2. V3 and V4
   *over interventricular septum

Question 25

What are the left lateral leads?

Answer 25

1. V5 and V6
   *Over the left ventricle

Question 26

What leads are looking at the anterior part of the heart?

Answer 26

1. V1
2. v2
3. V3
4. V4

Question 27

What leads are looking over the left lateral part of the heart?

Answer 27

1. I
2. aVL
3. V5
4. V6

Question 28

What leads are looking over the inferior portion of the heart?

Answer 28

1. II
2. III
3. aVF

Question 29

Where is the average direction of the vectors pointing to during ventricular depolarization?

Answer 29

1. Downward and to the patients left

Question 30

What are some variations in the heart placement and how could it affect the vector?

Answer 30

1. Vertical heart (tall and slim patients)
2. Horizontal heart (larger patients)
   *The mean vector is also displaced in the same direction

Question 31

How can hypertrophy affect vector?

Answer 31

1. The greater depolarization activity of the hypertrophied side displaces the mean QRS vector towards the hypertrophied side

Question 32

How can an area of infarction affect vector?

Answer 32

1. The unopposed vectors from the other side draw the mean QRS vector away from the infarct

Question 33

What are the steps to determining axis?

Answer 33

1. Look at lead I
2. Look at lead aVF

Question 34

What is the normal deflection in lead I and aVF?

Answer 34

I: upright
AVF: upright

Question 35

If the QRS complex in lead I is upright or downward what side of the heart is it on?

Answer 35

Upright: Left
Downward: Right

Question 36

If the QRS complex in aVF is upright or downward is pointing up or down? (towards positive pole)

Answer 36

Upright: down/bottom of circle (towards positive electrode)
Downward: up/top of circle (towards negative electrode)

Question 37

What are some causes of axis deviation?

Answer 37

1. Abnormal position of the heart
2. Ventricular hypertrophy
3. Conduction blocks
4. MI

Question 38

How to find precise axis determination?

Answer 38

1. Find the most isoelectric limb lead (or the smallest)
2. The axis is 90 degrees from the orientation of the most isoelectric limb lead
3. A “little” positive or negative (move 10 degrees in the direction of the most isoelectric lead)
   *larger component is <2x in measurement
4. A “lot” positive or negative (move 20 degrees)
   *larger component is >2x in measurement

Question 39

How to check your work with axis?

Answer 39

1. Look at the lead closest to the direction that the axial arrow is pointing
   *lead should be the tallest
2. Look at the lead that is directly opposite of the axis
   *That lead should be the deepest