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Cardiovascular > ECG > Flashcards

ECG Flashcards

1
Q

describe how repolarisation spreads through the heart tissue

A

epicardium to endocardium

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2
Q

describe how depolarisation spreads through the heart tissue

A

endocardium to epicardium

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3
Q

what is an ECG

A

recording of potential changes detected by electrodes positioned on the body surface, allows monitoring of heart activity

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4
Q

where do the potentials detected arise from

A

currents that flow when the membrane potential of myocardial tissue is changing (de/repolarisation)

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5
Q

why does the left ventricle have a bigger influence on the ECG

A

as bigger mass

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6
Q

can you detect the electrical activity in the nodes

A

no too small

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7
Q

is it the intra and extracellular current that is detected by an ECG

A

extra

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8
Q

what is an electric dipole

A

electrical vector-separated charges, move from atria to ventricles, positive charge first

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9
Q

what are the components of the vector electrical dipole

A

magnitude and direction

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10
Q

what allows the electrical axis of the heart to be estimated

A

lines of potential created by the cardiac dipole and their direction

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11
Q

what determines the mass of the electrical vector

A

the mass of the cardiac muscle

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12
Q

what determines the direction of the electrical vector

A

overall activity of the heart

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13
Q

describe the direction of depolarisation during the P wave on an ECG

A

atrial depolarisation moving towards the recording electrode

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14
Q

describe the direction of depolarisation during the Q wave on an ECG

A

left to right depolarization of the interventricular septum moving slightly away from the recording electrode

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15
Q

describe the direction of depolarisation during the R wave on an ECG

A

depolarization of the main ventricular mass moving towards the recording electrode

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16
Q

describe the direction of depolarisation during the S wave on an ECG

A

depolarization of ventricles at the base of the heart moving away from the recording electrode

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17
Q

describe the direction of repolarisation during the T wave on an ECG

A

ventricular repolarization moving in a direction opposite to that of depolarization accounts for the usually observed upward deflection

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18
Q

what is an ECG lead

A

the electrical picture obtained of the heart, not the wire

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19
Q

what type of deflect does depolarisation cause when moving towards the electrode

A

upward deflect

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20
Q

what type of deflect does depolarisation cause when moving away from the electrode

A

downward deflection

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21
Q

describe an isopotential deflection

A

no movement of current, no deflection

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22
Q

what are the bipolar leads

A

standard limb leads (I,II and III)

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23
Q

decsribe the reletionship between the augmented voltage leads

A

one recording two linked as reference (three all together)

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24
Q

what are the three augmented voltage leads

A

aVright, aVleft, aVfoot

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25
Q

are the aV leads unipolar or bipolar

A

unipolar

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26
Q

are the chest leads unipolar or bipolar

A

unipolar

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27
Q

what leads provide a picture of the heart from a vertical plane

A

I, II, III, aVR, aVL, and aVF

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28
Q

what leads provide a picture of the heart from a horizontal plane

A

V1 to V6 (chest leads)

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29
Q

what is the recording electrode for lead 1

A

RA-ve to LA+ve

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30
Q

what is the recording electrode for lead 2

A

RA-ve to LL+ve

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31
Q

what is the recording electrode for lead 3

A

LA-ve to LL+ve

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32
Q

what is bipolarity

A

A lead composed of two electrodes of opposite polarity is called bipolar lead

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33
Q

what is unipolarity

A

A lead composed of a single positive electrode and a reference point is a unipolar lead

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34
Q

what is the right legs role in an ECG

A

is earthed

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35
Q

from which direction does lead 2 see the heart

A

from an inferior direction

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36
Q

why is the p wave an positive deflection when shown in lead 2

A

as depolarisation spreads from SA node inferiorly and to the left

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37
Q

what is a normal duration for a P wave in an ECG and what does it represent

A

time for atrial muscle depolarisation. normally less than 0.120s

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38
Q

what is the downward deflection preceding and R wave called

A

Q wave

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39
Q

what is an R wave

A

an upwards deflection irrespective of whether it is proceeded by a Q wave

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40
Q

what is an s wave

A

a downward deflection following an R wave

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41
Q

what does the QRS complex represent

A

ventricular depolarisation

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42
Q

how long does a normal QRS complex last

A

0.1s or less

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43
Q

what causes the Q wave as seen via lead 2

A

as ventricular depolarisation starts in the inter ventricular septum and spreads from left to right

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44
Q

describe the R wave and what causes it

A

following the Q wave the main free walls of the ventricles depolarise causing a tall and narrow R wave

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45
Q

describe the S wave and what causes it

A

finally the ventricles at the base of the heart depolarize, producing a small and narrow S wave

46
Q

what does the T wave represent

A

ventricular repolarisation

47
Q

describe the deflection of the T wave seen from lead 2

A

an upward (positive) deflection because the wave of repolarization is spreading away from the recording electrode

48
Q

where does the PR interval start and end

A

from start of P wave to the start of the QRS complex

49
Q

what does the PR complex reflect

A

time for the SA node impulse to reach the ventricles

50
Q

what is the PR interval normally

A

0.12 – 0.2 s

51
Q

what is the PR interval strongly influenced by

A

delay in conduction through the AV node

52
Q

what is the position of the ST segment

A

is from the end of the QRS complex to the start of the T wave

53
Q

describe the ST segment

A

normally isoelectric – elevation, or depression, is diagnostically important

54
Q

what is the QT interval

A

from the start of the QRS complex to the end of the T wave

55
Q

what does the QT interval reflect

A

primarily reflects the time for ventricular depolarization and repolarization

56
Q

what is the normal duration of the QT interval in males and females

A

0.44s in males, 0.46 in females

57
Q

what does prolongation of the QT interval predispose an individual to

A

disturbances of cardiac rhythm

58
Q

describe goldberger’s method

A

one +ve electrode (recording), two others linked as –ve. This effectively positions the reference (linked) electrode in the center of the heart to which the recording electrodes ‘look’

59
Q

does the machine use the positive or negative electrode to see the lead

A

positive, negative used as a reference. Line of site= neg to pos electrode or in unipolar average of neg electrodes to pos electrodes (e.g augmented)

60
Q

what is the negative reference for the chest leads

A

average of all limb leads, same for all chest electrodes

61
Q

what is the hexaxial reference system

A

6 views of the heart in the frontal plane via standard (1-3) and augmented leads

62
Q

describe aVR waves

A

negative as predominant vector is depolarisation moving away from the recording electrode

63
Q

describe lead 2 waves

A

are positive and well resolved – predominant vector is depolarization moving towards the recording electrode

64
Q

what are lateral leads and which leads are they

A

I and aVL- each has the recording electrode on the left arm and views the heart from the left

65
Q

what are inferior leads and which leads are they

A

II, III and aVF- each has the recording electrode on the left foot and views the heart from an inferior direction

66
Q

describe the view of the heart provided by the chest leads

A

different positions in the horizontal plane

67
Q

what do leads V1 and V2 look and from what direction

A

the interventricular septum from the right

68
Q

what do leads V3 and V4 look and from what direction

A

anterior of the heart

69
Q

what do leads V5 and V6 look and from what direction

A

later aspect (left ventricle) of the heart

70
Q

in V1 what is the first positive defection in the QRS complex and the negative deflection that immediately follows

A

R wave then S wave

71
Q

what happens to the R wave and S wave that follow as you go from V1 to V6

A

R wave progressively increases and S wave progressively decreases

72
Q

where is V1 placed

A

fourth intercostal space immediately right of sternum

73
Q

where is V2 placed

A

fourth intercostal space immediately left of sternum

74
Q

where is V3 placed

A

mid way between V2 and V4

75
Q

what is V4 placed

A

fifth intercostal space in the midclavicular line

76
Q

where is V5 placed

A

same horizontal level as V4 in the anterior axillary line

77
Q

where is V6 placed

A

same horizontal level as V4 in the mid axillary line

78
Q

where are the ECG waves bets seen

79
Q

how long does a P wave usually last

A

0.8 to 10 sec

80
Q

how long does a QRS complex last

A

less than 0.10 sec

81
Q

at what part of the ECG do the ventricle contract

A

ST segment (systole)

82
Q

at what part of the ECG do the ventricles relax

A

TP segment (diastole)

83
Q

what is the P wave and how long does it usually last

A

atrial depolarization (0.08 - 0.10 sec)

84
Q

what does the QRS complex represent

A

ventricular depolarisation

85
Q

what does the T wave represent

A

ventricular repolarisation

86
Q

what does the QT interval represent

A

depolarisation and repolarisation

87
Q

how do you calculate heart rate from an ECG

A

300/number of large squares between beat (R-R intervals)

88
Q

what time does a big box on an ECG represent

A

0.2 seconds

89
Q

what time does a small box on an ECG represent

A

0.04 seconds

90
Q

what in the ECG rhythm strip

A

prolonged recording of one lead (usually lead 2) which allows you to detect rhythm disturbance

91
Q

what reasons (3) show the need for 12 leads

A
  • to determine the axis of the heart
  • look for any ST segment or T wave that changes in relation to any specific region of the heart (crucial for ischaemic heart disease)
  • look for any voltage criteria changes (crucial for chamber hypertrophy)
92
Q

what are the 6 key steps in analysing an ECG

A

1 Verify patient details: name and date of birth

2 Check date and time ECG was taken

3 Check the calibration of the ECG paper

4 Determine the axis, if possible

5 Work out the rhythm

6 Look at individual leads for voltage criteria changes OR any ST or T-wave changes

93
Q

what 7 questions do you ask yourself to workout rhythm

A 
1 Is electrical activity present?
2 Is the rhythm regular or irregular?
3 What is the heart rate?
4 P-waves present?
5 What is the PR interval?
6 Is each P-Wave followed by a QRS complex? 
7 Is the QRS duration normal?
94
Q

how many small squares should the PR interval be

A

3-5 small/ 1 big

95
Q

what are three heart diseases which have a normal resting ECG

A

myocardial infarction (may or may not have ECG changes). intermittent rhythm disturbance, stable angina (do exercise ECG)

96
Q

how long is each small square

A

0.04 seconds

97
Q

how long is each big square

A

0.2 seconds

98
Q

how do you calculate the heart rate when its irregular

A

count number or QRS complexes in 30 big squares and times by 10

99
Q

what leads are inferior and what coronary artery is this

A

II, III, aVF

right coronary artery

100
Q

what leads are anterior and what coronary artery is this

A

V1-4

left anterior descending

101
Q

what leads are lateral and what coronary artery is this

A

I, V5-6

circumflex

102
Q

how is right axis deviation shown on an ECG

A

lead I down, lead aVF up

103
Q

how is left axis deviation shown on an ECG

A

lead I up, lead aVF down

104
Q

how long is the PR interval usually

A

bigger than 3 small, smaller than 1 big

105
Q

what are the 6 steps in reading an ECG

A

1-verify patient details
2-check date and time when ECG was taken
3-check calibration, 25mm per second and 1cm/1mV
4-determin the axis- look at lead I and aVF- if both upright axis normal
5-rhythm strip; electrical activity? Regular/ irregular? Rate? P-waves present? What is the PR interval? Each P wave followed by a QRS complex? QRS duration normal?
6-individual leads for voltage criteria changes OR ST or T wave changes

106
Q

when is ST elevation significant

A

when at least 2mm in 2 adjacent chest leads
or
1mm in limb leads

107
Q

what does no P waves and irregularity mean on an ECG

108
Q

what does tall QRS’s in V4, 5 and 6 mean

109
Q

what leads show anteroseptal

110
Q

what leads show anterolateral

A

I, aVL, V1-6

111
Q

which coronary artery is usually affected in an inferior MI

A

right coronary

112
Q

what coronary artery is usually affected in an anterior MI

A

left coronary

Cardiovascular (34 decks)

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