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Cardiology > Electrocardiography I and II > Flashcards

Electrocardiography I and II Flashcards

1
Q

3 determinants of amplitude of electrical vectors

A
  1. mass of muscle generating signal
  2. conduction velocity
  3. degree of cancellation of electrical forces
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2
Q

What do we see if an electrical vector is perpendicular to the orientation of the lead?

A

no deflection on EKG

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3
Q

What do we see if an electrical vector is at an angle to the orientation of the lead?

A

amplitude of deflection correlated with the projection (parallel component) of the vector

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4
Q

What is the role of the right leg in the lead system?

A

not directly involved in any lead –> is simply the grounding to account for ambient electrical activity

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5
Q

Vector orientation and setup of: Lead 1

A

negative pole on right arm, positive pole on left arm –> vector going right to left

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6
Q

Vector orientation and setup of: Lead 2

A

negative pole on right arm, positive pole on left leg –> vector pointing down and toward left from right arm

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7
Q

Vector orientation and setup of: Lead 3

A

negative pole on left arm, positive pole on left leg –> vector pointing down and toward right from left arm

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8
Q

Vector orientation and setup of: aVR

A

negative pole on left arm/leg, positive pole on right arm –> vector pointing up and toward right arm

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9
Q

Vector orientation and setup of: aVL

A

negative pole on right arm/left leg, positive pole on leftarm –> vector pointing up and toward leftarm

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10
Q

Vector orientation and setup of: aVF

A

negative pole on arms, positive pole on left leg –> vector pointing down

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11
Q

Angular orientation of: lead 1

A

0

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12
Q

Angular orientation of: lead 2

A

60

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13
Q

Angular orientation of: lead 3

A

120

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14
Q

Angular orientation of: aVF

A

90

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15
Q

Angular orientation of: aVR

A

-150

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16
Q

Angular orientation of: aVL

A

-30

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17
Q

Setup of V leads

A

negative poles on left leg and arms –> creates virtual negative pole/central terminal of wilson in chest –> 6 positive poles V1-V6 on chest

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18
Q

Placement of: V1

A

4th intercostal space, right of sternum

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19
Q

Placement of: V2

A

4th intercostal space, left of sternum

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20
Q

Placement of: V3

A

halfway between v2 and v4

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21
Q

Placement of: V4

A

5th intercostal space, midclavicular

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22
Q

Placement of: V5

A

lateral to v4 in anterior axillary line

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23
Q

Placement of: V6

A

lateral to v4 in the mid axillary line

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24
Q

Is the SA node depolarization visible on EKG?

A

no –> slow conduction and small voltage –> not visible

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25
Q

Is atrial depolarization visible on EKG?

A

yes –> P wave

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26
Q

Is the atrial repolarization visible on EKG?

A

no

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27
Q

Is the AV node depolarization visible on EKG?

A

no

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28
Q

Is the his/bundle depolarization visible on EKG?

A

no

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29
Q

Is ventricular depolarization visible on EKG?

A

yes –> QRS complex

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30
Q

Is the ventricular plateau visible on EKG?

A

yes –> ST –> flat portion b/c all ventricular muscle is at same potential so no voltage

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31
Q

Is the ventricular repolarization visible on EKG?

A

yes –> T wave

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32
Q

Which wave is an initial downward deflection in QRS?

A

Q wave

33
Q

Which wave is the first upward deflection in QRS?

A

R wave

34
Q

Which wave is a downward deflection after an R in QRS?

A

S wave

35
Q

Which wave is a second upward deflection in QRS?

A

R’

36
Q

How do we know if we are using standard paper/paper speed for an EKG reading?

A

initial square pulse is 2 boxes tall (10mm) and 1 box wide (5mm)

37
Q

What is the time passage associated with one big box on EKG (5mm)?

A

200 ms

38
Q

What is the time passage associated with one small box on EKG (1mm)?

A

40ms

39
Q

How many big boxes on EKG is 1 second of time passage?

A

5 boxes

40
Q

Which leads are used for rhythm strips?

A

lead II or V1 b/c they have good p waves

41
Q

Which leads look at the lower part of the inferior wall of the heart?

A

leads II, III, and aVF

42
Q

Which leads look at the septal part of the heart?

A

V1 and V2

43
Q

Which leads look at the anterior wall of the heart?

A

V3 and V4

44
Q

Which leads look at the lateral wall of the heart?

A

I, aVL, V5, V6

45
Q

5 steps in analysing an EKG

A
  1. rate
  2. rhythm
  3. intervals (PR, QRS, QT)
  4. QRS axis
  5. configuration (P wave, QRS, ST segment, T wave)
46
Q

What does the RR interval tell us?

A

heart rate –> 1 box = 300 beat/min, 5 box =60 beat/min ~ hr = 300/# of large boxes OR # of intervals in a 10 second strip * 6

47
Q

P waves are upright during normal sinus rhythm with normal AV conduction in which leads?

A

I, II, aVF b/c p waves should are going from upper right to lower left of heart –> pointing in the direction of I/II/aVF (between 0 and 90 degrees)

48
Q

What is the PR interval?

A

time between beginning of P wave and beginning of QRS complex (regardless of whether there is a q wave on a given lead) –> spread of depolarization through the atrium + delay in AV node –> can tell you if there is abnormal conduction in AV node

49
Q

What is the QRS interval?

A

from beginning of QRS to end of QRS –> tells how long it takes to achieve ventricular depolarization

50
Q

What is the QT interval?

A

time between beginning of QRS and end of T wave –> describes duration of ventricular depolarization/repolarization

51
Q

Normal length of PR interval

A

0.12-0.2 sec (3 little boxes to one big box)

52
Q

Normal length of QRS interval

A

<0.10 sec (2-3 little boxes)

53
Q

What does a PR interval >0.2 tell us?

A

AV nodal conduction velocity is slower than normal

54
Q

What happens to QT as heart rate increases?

A

increase hr –> reduce AP duration –> shorter QT

55
Q

At a hr of about 60 beats/min, how long should a QT be (approximately)

A

2 big boxes (around 400 ms)

56
Q

What does a QRS >012 seconds tell us?

A

slow ventricular depolarization –> not using left and right bundle branches AKA bundle branch block or ventricular origin

57
Q

What does a prolonged QT tell us?

A

prolonged ventricular APs

58
Q

What is the frontal plane QRS axis?

A

the orientation of the greatest net QRS amplitude in the frontal plane

59
Q

What can cause a shifted QRS axis?

A

fascicular block , infarctions, left/right ventricular hypertrophy, ventricular tachycardia, etc –> anything that changes the direction of ventricular depolarization

60
Q

What is the easiest way to determine the QRS axis?

A

look for the isoelectric lead (the lead that has 0 amplitude or positive/negative deflections that are small and cancel each other out) –> this one is 90 degrees to the direction of the depolarization

61
Q

Normal QRS morphology; what does it look like and which lead does it show up on: septal depolarization

A

first part of ventricular activation is septal activation –> goes from left ventricle toward right ventricle –> in direction of V1 –> upward deflection of V1 and possible downward deflection in lateral leads (since vector is going away from these)

62
Q

What does absence of R wave in V1 during QRS suggest?

A

septal infarct –> there is no conduction across septum from left to right

63
Q

Where does the net vector in the middle of QRS point and how does it appear?

A

towards apex of LV–> increasing upward deflection in progression v3/4/5/6 (max on v5) and decreasing downward deflection in progression v1/2/3

64
Q

Where does the net vector at late QRS point and how does it appear?

A

up and toward left (along left ventricular wall) –> positive deflection in v5/v6

65
Q

What does absence of progression of R wave in chest leads during QRS suggest?

A

anterior wall infarct

66
Q

Why are t-waves upright if they are repolarization?

A

the most recently depolarized area repolarizes first –> opposite direction of spread, from positive epicardium to negative endocardium –> opposite deflection than expected

67
Q

Why is the sequence of repolarization and direction of depolarization different in the heart?

A

AP durations are different –> epicardial AP is shorter than endocardial AP so even though it starts after endocardium, its AP ends earlier and starts to repolarize before the endocardium

68
Q

In what scenarios would we see inverted t waves/pointing downward)

A

anytime the QRS is longer than .120seconds –> t wave is a very sensitive indicator

69
Q

Normal range of QRS axis

A

-30 to 90 degrees

70
Q

What is right axis deviation?

A

any QRS axis that is >90 degrees

71
Q

What is left axis deviation?

A

any QRS axis that is <-30 degrees

72
Q

T/F twaves should go in the same direction as qrs

A

mostly true except in the chest leads –> there should be a normal progression of positive t waves whether or not qrs is pointing up or down

73
Q

What kind of AV block? every P followed by QRS but PR > 0.20/1 big box

A

first degree AV block

74
Q

What kind of AV block? some Ps followed by QRSs, some not aka intermittent block

A

second degree AV block

75
Q

What kind of AV block? complete heart block, Ps not followed by QRSs at a regular interval

A

third degree AV block –> could have absent QRS or random QRSs or irregular intervals

76
Q

Which leads reveal bundle branch patterns?

A

I, V1, V6

77
Q

What does a right bundle branch block look like?

A

RSR’ on V1 –> delayed right ventricle depolarization creates R’

78
Q

What does a left bundle branch block look like?

A

large wide S wave on V1, large wide R wave on 1 and V6

Cardiology (41 decks)

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