Physiological Basis of EKG

Question 1

What are the nine EKG electrodes?

Answer 1

RA, LA, LL

V1, V2, V3, V4, V5, V6

Question 2

What are the heart rates of the big boxes on an EKG tracing?

Answer 2

300, 150, 100, 75, 60 , 60 , 43

Question 3

What is the directional axis of the aVL tracing?

Answer 3

• 30 degrees

- left axis deviation

Question 4

What is the directional axis of the I tracing?

Answer 4

0 degrees

Question 5

What is the directional axis of the aVR tracing?

Answer 5

• 150 degrees

- extreme right axis deviation

Question 6

What is the directional axis of the II tracing?

Answer 6

60 degrees

-normal axis

Question 7

What is the directional axis of the aVF tracing?

Answer 7

90 degrees

Question 8

What is the directional axis of the III tracing?

Answer 8

120 degrees

-right axis deviation

Question 9

What does the I tracing represent?

Answer 9

bipolar representation from RA to LA

Question 10

What does the II tracing represent?

Answer 10

bipolar representation from RA to LL

Question 11

What does the III tracing represent?

Answer 11

bipolar representation from LA to LL

Question 12

What does the aVR tracing represent?

Answer 12

the average of the LA and LL electrodes, heading in the direction of the RA electrode

Question 13

What does the aVL tracing represent?

Answer 13

the average of the RA and LL electrodes, heading in the direction of the LA electrode

Question 14

What does the aVF tracing represent?

Answer 14

the average of the RA and LA electrodes, heading in the direction of the LL electrode

Question 15

What do the precordial (chest) leads detect?

Answer 15

what’s going on electrically immediately beneath the electrode’s placement

Question 16

What is represented by the P wave on the EKG?

Answer 16

atrial depolarization

Question 17

What is represented by the QRS complex on the EKG?

Answer 17

ventricular depolarization

Question 18

What is the relationship bw the duration of the QRS complex in relation to the P wave, and why?

Answer 18

they are similar, bc even though the ventricular ctx is larger, the conduction velocity of the electric impulse is faster in the ventricles than in the atria

Question 19

What is represented by the T wave on an EKG?

Answer 19

ventricular repolarization

Question 20

What is the PR interval on an EKG?

Answer 20

time bw initial atrial depolarization and initial ventricular depolarization

Question 21

What does the length of the PR interval represent?

Answer 21

the time for AV node conduction

Question 22

What is the QT interval on an EKG?

Answer 22

initial ventricular depolarization to final ventricular repolarization

Question 23

What does the ST segment represent on an EKG?

Answer 23

the plateau of ventricular action potential

phase 2

Question 24

What is the normal time duration of the P wave?

Answer 24

0. 06-0.11 seconds

1. 5-2.75 small boxes

Question 25

What is the normal time duration of the PR segment?

Answer 25

0.12-0.20 seconds | 3-5 small boxes

Question 26

What is the normal time duration of the QRS wave?

Answer 26

0.08-0.10 seconds | 2-2.5 small boxes

Question 27

What is the normal time duration of the QT segment?

Answer 27

0.36-0.44 seconds | 9-11 small boxes

Question 28

What is the normal time duration of the ST segment?

Answer 28

0.08 seconds | 2 small boxes

Question 29

What is the normal time duration of the T wave?

Answer 29

0. 1-0.25 seconds | 2. 5-6.25 small boxes

Question 30

What will happen to the EKG tracing if the conduction velocity through the atria decreases?

Answer 30

P wave will get longer in duration

Question 31

What will happen to an EKG tracing if the right atrium is enlarged?

Answer 31

P wave will get taller

Question 32

What does a wide QRS complex indicate?

Answer 32

bundle branch block

Question 33

What will happen to an EKG tracing in the case of left ventricular hypertrophy?

Answer 33

tall QRS complex

Question 34

What will happen to an EKG tracing in the case of lost ventricular myocardium?

Answer 34

short QRS complex

Question 35

What does a tall T wave indicate?

Answer 35

hyperkalemia

Question 36

What will happen to an EKG if the patient has an AV block?

Answer 36

PR segment will lengthen horizontally

Question 37

What would happen to an EKG tracing in a case of hypokalemia?

Answer 37

QT segment will lengthen horizontally

Question 38

What might a depressed ST segment indicate?

Answer 38

hypokalemia

Question 39

What might an elevated ST segment indicate?

Answer 39

MI or pericarditis

Question 40

What does an EKG electrode detect?

Answer 40

the extracellular voltage

Question 41

What is the mechanism for how an EKG electrode detects a positive voltage during depolarization?

Answer 41

as the atria or ventricles depolarize from upper R to lower L, the extracellular space on the L now has a positive charge when compared to the extracellular space on the R

Question 42

What two leads are considered when determining the deviation of axis?

Answer 42

I and aVF

Question 43

What is the deviation of the axis if the QRS complexes in both I and aVF are upright?

Answer 43

normal

Question 44

What is the deviation of the axis if the QRS complex in I is upright, but aVF is inverted?

Answer 44

left axis deviation

Question 45

What is the deviation of the axis if the QRS complex in I is inverted, but aVF is upright?

Answer 45

right axis deviation

Question 46

What is the deviation of the axis if the QRS complex in I is inverted and also inverted in aVF?

Answer 46

extreme right axis deviation

Question 47

What kind of axis deviation would left ventricular hypertrophy cause?

Answer 47

left axis deviation

Question 48

What kind of axis deviation would right ventricular hypertrophy cause?q

Answer 48

right axis deviation