Chapter 1 EKG

Question 1

from the point of an electrocardiographer what are the 3 types of cells in the heart?

Answer 1

Pacemaker cells (electrical power source)
electrical conducting cells
myocardial cells

Question 2

define Action potential?

Answer 2

record one electrical cycle of depolarization and repolarization from a single cell.

Question 3

what does the action potential of pacemaker cells look like?

Answer 3

electrical charge drops to a minimal negative potential of -60mV.

Question 4

what is the frequency of the SA node?

Answer 4

60-100Hz

the denervated heart will beat at 100bpm.

Question 5

what is the bundle of nerves called that go from the Left to right atrium?

Answer 5

Bachmann’s bundle.

Question 6

what element plays a role in excitation-contraction coupling?

Answer 6

Calcium.

Question 7

how much time does one small square represent?

Answer 7

0.04 seconds

Question 8

how much time does one large square represent?

Answer 8

0.2 seconds (0.04 x 5)

Question 9

the vertical axis, one small square represents?

Answer 9

0.1mV

Question 10

the vertical axis, one large square represents?

Answer 10

0.5mV

Question 11

what part of the heart depolarizes 1st?

Answer 11

the right atrium since that is where the SA node is. The first half of the P-wave is the right atrium depolarization, and the other half is the left atrium.

Question 12

why is the conduction delay in the AV node necessary?

Answer 12

to allow the ventricles to fill up with blood from the atria before they contract.

Question 13

Name the 3 parts of the ventricular conducting system?

Answer 13

• Bundle of His
• Bundle branches
• Terminal purkinje fibers

Question 14

Name the 3 branches of the left bundle branch?

Answer 14

Septal fascicle: depolarizes the interventricular septum
Anterior fascicle: runs along anterior wall of left ventricle
Posterior fascicle: posterior wall of left ventricle

Question 15

Why does the QRS complex have such a high amplitude?

Answer 15

do to higher muscle mass in the ventricles. Most of the QRS is the left ventricle due to higher muscle mass.

Question 16

the voltage of the P or Q wave is lower?

Answer 16

T wave is less than that of the Q-wave.

Question 17

when it comes to ECG what is the difference between a segment and an interval?

Answer 17

Segment = straight line
interval = encompasses at-least one wave plus.

Question 18

what are the 3 intervals/segments?

Answer 18

• PR interval (includes P wave + straight line connecting to QRS segment), from atrial depol to vent. deplo.
• PR segment time delay of AV node.
• QT interval includes the QRS complex, the ST segment and the T-wave.
• QRS interval measures QRS complex duration.

Question 19

how do waves show up on the EKG?

Answer 19

waves of depolarization moving towards positive electrode show upward deflection.

Question 20

where should a electrode be placed to create a bi-phasic wave.

Answer 20

perpendicular to the wave of depolarization.

Question 21

Lead I angle?

Answer 21

zero degrees

Question 22

Lead II angle?

Answer 22

60 degrees

Question 23

Lead III angle?

Answer 23

120 degrees

Question 24

how are augmented leads set up?

Answer 24

a single lead is chosen to be positive and all the others are made negative, with their average essentially serving as the negative electrode.

Question 25

Lead aVL setup?

Answer 25

left arm positive and other limbs negative (-30 degrees)

Question 26

lead aVR setup?

Answer 26

right arm positive and the other limbs negative (-150 degrees)

Question 27

lead aVF setup?

Answer 27

legs positive and other limbs negative. (+90 degrees)

Question 28

what are the inferior leads?

Answer 28

Lead II, III, aVF.

Question 29

what are the left lateral leads?

Answer 29

Lead I and aVL, V5, V6

Question 30

what are the right-sided limb leads?

Answer 30

aVR, V1

Question 31

where is V1 electrode placed?

Answer 31

4th IC space right of sternum

Question 32

where is V2 electrode placed?

Answer 32

4th IC space left of sternum

Question 33

where is V3 electrode placed?

Answer 33

placed between V2 and V4

Question 34

where is V4 electrode placed?

Answer 34

5th IC space in the midclavicular line

Question 35

where is V5 electrode placed?

Answer 35

between V4 and V6

Question 36

where is V6 electrode placed?

Answer 36

5th IC space in midaxillary line

Question 37

what does all of the 6 precordial leads see?

Answer 37

V1 = over right ventricle V2, V3 = over the interventricular septum V4 = over the apex of left ventricle V5, V6 over the lateral left ventricle

Question 38

what are the anterior leads?

Answer 38

V2, V3, V4

Question 39

how long is the PR interval?

Answer 39

0.12-0.2 seconds

Question 40

what direction does the interventricular septum depolarize?

Answer 40

left to right do to the left bundle branch being responsible for rapidly delivering the wave to this part. this is seen as a Q wave which is RARELY seen in Lead II.

Question 41

what is R wave progression?

Answer 41

the pattern of progressively increasing R wave amplitude moving right to left in the precordial leads. V1 has small R-wave, Lead V5 has largest R-wave.

Question 42

Duration of the QRS complex?

Answer 42

0.06 - 0.1 seconds.

Question 43

why does both ventricular depolarization and repolarization cause a deflection in the same direction?

Answer 43

depolarization and repolarization occur in opposite direction. first to depolarize is the last to repolarize.

Question 44

QT interval duration?

Answer 44

heart rate dependent. Faster beating heart means shorter QT interval.