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MSS - CV Exam 1 > Physiologic Basis for ECG > Flashcards

Physiologic Basis for ECG Flashcards

1
Q

what does ECG measure?

A

potential differences between recording electrodes generated by currents from the heart to body surface

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2
Q

ECG measurement?

A

SUM of all electrical potentials

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3
Q

different ECG leads

A

view electrical vectors of heart from different angles

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4
Q

what contributes to the rate and rhythm of ECG?

A

1 - automaticity
2 - conduction system order and timing
3 - functional syncytium

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5
Q

P wave

A

atrial depolarization

immediately precedes atrial contraction

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6
Q

QRS complex

A

ventricular depolarization
atria repolarizing simultaneously

immediately precedes ventricular contraction

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7
Q

T wave

A

ventricular repolarization

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8
Q

ventricular contraction?

A

remain until after T wave of repolarization

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9
Q

what happens during P wave

A

begins at SA node, spreads toward AV node

right atrium begins to depolarize before left atrium

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10
Q

what happens during QRS wave?

A

depolarization at IV septum (Q wave)
AVERAGE current flows from base of heart to apex (R wave)
current reverses flows toward outer wall of ventricles near base (S wave)

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11
Q

what is the Q wave

A

interventricular septum depolarization

begins at IV septum and endocardial surfaces

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12
Q

what is the R wave

A

current flows from base of heart to apex

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13
Q

what is the S wave

A

current reverses, flows toward outer walls of ventricle near the base

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14
Q

first deflection downward?

A

Q wave

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15
Q

first upward deflection?

A

R wave

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16
Q

second upward deflection?

A

R’

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17
Q

first downward deflection following an upward deflection?

A

S wave

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18
Q

if entire configuration consists solely of one downward deflection?

A

QS wave

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19
Q

ventricular repolarization?

A

T wave

  • begins in last area that was depolarized
  • travels toward base of heart in opposite direction of depolarization
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20
Q

P wave

A

atrial depolarization

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21
Q

PR interval?

A

atrial depolarization and AV node delay

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22
Q

QRS?

A

ventricular depolarization

and atrial repolarization

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23
Q

QT interval?

A

ventricular depolarization/repolarization

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24
Q

ST segment?

A

ventricular contraction and ejection

**isoelectric line

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25
Q

RR interval?

A

heart rate

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26
Q

TP interval

A

ventricular relaxation and filling

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27
Q

T wave

A

ventricular repolarization

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28
Q

Units of ECG?

A

1 small square = 0.04s (1mm)
1 large square = 0.2s
5 large squares = 1s

2 large squares vertically = 1mV

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29
Q

importance of PR interval?

A

atrial depolarization to ventricular depolarization
-includes delay in conduction that occurs at AV node

important for identifying AV blocks:
primary, secondary, tertiary

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30
Q

what is the normal PR interval

A

0.12-0.2 seconds

3-5mm on EKG paper

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31
Q

what pathology can be found on PR interval?

A

AV blocks:
primary
secondary (Mobitz I and II)
tertiary

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32
Q

importance of ST segment?

A

time from end of ventricular depolarization to start of ventricular repolarization

generally horizontal or gently up-sloping in all leads

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33
Q

deviation from isoelectric line in ST segment?

A

indicates myocardial ischemia or injury

S-T elevation:
MI
acute pericarditis
LVH
hyperkalemia
34
Q

importance of QT interval

A

time from beginning of ventricular depolarization to end of ventricular repolarization

all electrical events in the ventricles

heart rate dependent

more time repolarization phase

35
Q

long QT syndrome?

A

congenital:
mutant Na+ failure to inactivate
K+ defective repolarization

acquired:
electrolyte imbalance
pharmacologic

36
Q

normal PR interval?

A

0.12 - 0.2s

37
Q

normal QT interval?

A

less than or equal to .44 s

38
Q

normal QRS?

A

0.08 - 0.12s

39
Q

normal P wave?

A

0.08 - 0.10s

40
Q

estimation of heart rate based on number of boxes?

A 
1 - 300
2 - 150
3 - 100
4 - 75
5 - 60
6 - 50
7 - 43
8 - 38
9 - 33
10 - 30
41
Q

estimation of heart rate tip?

A

divide 300 by number of large boxes

ex/ 4 large boxes: 300/4 = 75 bpm

42
Q

second method for heart rate estimation?

A

three tick marks = 6 seconds

count number of RR intervals per 6 second interval
-multiply by 10

43
Q

wave or depolarization towards positive electrode?

A

records positive voltage

44
Q

wave of depolarization away from positive electrode?

A

negative voltage

45
Q

wave of repolarization away from positive electrode?

A

positive voltage

46
Q

wave or repolarization toward positive electrode?

A

negative voltage

47
Q

waves perpendicular to lead axis?

A

no net voltage

-isoelectric

48
Q

wave of depolarization perpendicular to positive electrode?

A

records biphasic wave (no net voltage)

positive deflection precedes negative deflection

49
Q

wave of repolarization perpendicular to positive electrode?

A

records biphasic wave

negative deflection precedes positive deflection

50
Q

12 leads of EKG?

A

bipolar standard limb (1+, 1-)
leads I, II, III

unipolar augmented leads (1+, 2-)
leads aVL, aVR, aVF

unipolar chest leads
V1-V6

51
Q

set up for 12 lead EKG?

A

2 arm electrodes and 2 leg electrodes

6 chest electrodes

52
Q

what do limb leads measure?

A

record electrical activity moving up/down and left/right in the coronal plane

53
Q

direction lead goes?

A

to its positive electrode

54
Q

lead at 0 degrees?

A

lead I

55
Q

lead at -30 degrees?

A

aVL

56
Q

lead at 60 degrees?

A

lead II

57
Q

lead at 90 degrees?

A

aVF

58
Q

lead at 120 degrees?

A

lead III

59
Q

lead at -150 degrees?

A

aVR

60
Q

what is einthoven’s triangle?

A

RA, LA, LL electrodes

sets up the standard limb leads I, II, III

61
Q

what makes up lead I?

A

LA + to RA -

angle of orientation = 0

62
Q

what makes up lead II?

A

LL + to RA -

angle of orientation = 60

63
Q

what makes up lead III?

A

LL + to LA -

angle of orientation 120

64
Q

set up for augmented leads?

A

1 positive electrode
2 negative electrodes

negative electrodes averaged together to create a composite reference lead

65
Q

aVL lead setup?

A

RA,LL - to LA +

angle of orientation = -30

66
Q

aVR lead setup?

A

LA, LL - to RA +

angle of orientation = -150

67
Q

aVF lead setup?

A

RA, LA - to LL +

angle of orientation = 90

68
Q

mnemonic for frontal plane leads?

A

Three Little Ones Ran Too Far

69
Q

what leads give inferior view of heart?

A

Lead II
Lead III
Lead aVF

70
Q

what gives left lateral view of heart?

A

Lead I

Lead aVL

71
Q

what gives right-sided view of heart?

A

lead aVR

72
Q

what do precordial leads measure?

A

electrical activity moving anteriorly/posteriorly in horizontal plane

73
Q

placement of chest electrodes?

A 
V1 - 4th intercostal, right of sternum
V2 - 4th intercostal left of sternum
V3 - between V2 and V4
V4 - 5th intercostal space midclavicular
V5 - between V4 and V6
V6 - 5th intercostal space, midaxillary
74
Q

V1 view of heart?

A

over right ventricle

75
Q

V2 and V3 view of heart?

A

iver interventricular septum

76
Q

V4 view of heart?

A

over apex of left ventricle

77
Q

V5 and V6 view of heart?

A

over lateral left ventricle

78
Q

orientation of right and left ventricles?

A

right - anterior and medial

left - posterior and lateral

79
Q

anterior view of heart leads?

A

V2, V3, V4**

80
Q

left lateral view of heart leads?

A

I, aVL, V5, V6**

81
Q

inferior view of heart leads?

A

II, III, aVF**

82
Q

right ventricular view of heart leads?

A

aVR, V1**

MSS - CV Exam 1 (14 decks)

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