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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
are the aV leads unipolar or bipolar
unipolar
26
are the chest leads unipolar or bipolar
unipolar
27
what leads provide a picture of the heart from a vertical plane
I, II, III, aVR, aVL, and aVF
28
what leads provide a picture of the heart from a horizontal plane
V1 to V6 (chest leads)
29
what is the recording electrode for lead 1
RA-ve to LA+ve
30
what is the recording electrode for lead 2
RA-ve to LL+ve
31
what is the recording electrode for lead 3
LA-ve to LL+ve
32
what is bipolarity
A lead composed of two electrodes of opposite polarity is called bipolar lead
33
what is unipolarity
A lead composed of a single positive electrode and a reference point is a unipolar lead
34
what is the right legs role in an ECG
is earthed
35
from which direction does lead 2 see the heart
from an inferior direction
36
why is the p wave an positive deflection when shown in lead 2
as depolarisation spreads from SA node inferiorly and to the left
37
what is a normal duration for a P wave in an ECG and what does it represent
time for atrial muscle depolarisation. normally less than 0.120s
38
what is the downward deflection preceding and R wave called
Q wave
39
what is an R wave
an upwards deflection irrespective of whether it is proceeded by a Q wave
40
what is an s wave
a downward deflection following an R wave
41
what does the QRS complex represent
ventricular depolarisation
42
how long does a normal QRS complex last
0.1s or less
43
what causes the Q wave as seen via lead 2
as ventricular depolarisation starts in the inter ventricular septum and spreads from left to right
44
describe the R wave and what causes it
following the Q wave the main free walls of the ventricles depolarise causing a tall and narrow R wave
45
describe the S wave and what causes it
finally the ventricles at the base of the heart depolarize, producing a small and narrow S wave
46
what does the T wave represent
ventricular repolarisation
47
describe the deflection of the T wave seen from lead 2
an upward (positive) deflection because the wave of repolarization is spreading away from the recording electrode
48
where does the PR interval start and end
from start of P wave to the start of the QRS complex
49
what does the PR complex reflect
time for the SA node impulse to reach the ventricles
50
what is the PR interval normally
0.12 – 0.2 s
51
what is the PR interval strongly influenced by
delay in conduction through the AV node
52
what is the position of the ST segment
is from the end of the QRS complex to the start of the T wave
53
describe the ST segment
normally isoelectric – elevation, or depression, is diagnostically important
54
what is the QT interval
from the start of the QRS complex to the end of the T wave
55
what does the QT interval reflect
primarily reflects the time for ventricular depolarization and repolarization
56
what is the normal duration of the QT interval in males and females
0.44s in males, 0.46 in females
57
what does prolongation of the QT interval predispose an individual to
disturbances of cardiac rhythm
58
describe goldberger's method
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
does the machine use the positive or negative electrode to see the lead
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
what is the negative reference for the chest leads
average of all limb leads, same for all chest electrodes
61
what is the hexaxial reference system
6 views of the heart in the frontal plane via standard (1-3) and augmented leads
62
describe aVR waves
negative as predominant vector is depolarisation moving away from the recording electrode
63
describe lead 2 waves
are positive and well resolved – predominant vector is depolarization moving towards the recording electrode
64
what are lateral leads and which leads are they
I and aVL- each has the recording electrode on the left arm and views the heart from the left
65
what are inferior leads and which leads are they
II, III and aVF- each has the recording electrode on the left foot and views the heart from an inferior direction
66
describe the view of the heart provided by the chest leads
different positions in the horizontal plane
67
what do leads V1 and V2 look and from what direction
the interventricular septum from the right
68
what do leads V3 and V4 look and from what direction
anterior of the heart
69
what do leads V5 and V6 look and from what direction
later aspect (left ventricle) of the heart
70
in V1 what is the first positive defection in the QRS complex and the negative deflection that immediately follows
R wave then S wave
71
what happens to the R wave and S wave that follow as you go from V1 to V6
R wave progressively increases and S wave progressively decreases
72
where is V1 placed
fourth intercostal space immediately right of sternum
73
where is V2 placed
fourth intercostal space immediately left of sternum
74
where is V3 placed
mid way between V2 and V4
75
what is V4 placed
fifth intercostal space in the midclavicular line
76
where is V5 placed
same horizontal level as V4 in the anterior axillary line
77
where is V6 placed
same horizontal level as V4 in the mid axillary line
78
where are the ECG waves bets seen
lead 2
79
how long does a P wave usually last
0.8 to 10 sec
80
how long does a QRS complex last
less than 0.10 sec
81
at what part of the ECG do the ventricle contract
ST segment (systole)
82
at what part of the ECG do the ventricles relax
TP segment (diastole)
83
what is the P wave and how long does it usually last
atrial depolarization (0.08 - 0.10 sec)
84
what does the QRS complex represent
ventricular depolarisation
85
what does the T wave represent
ventricular repolarisation
86
what does the QT interval represent
depolarisation and repolarisation
87
how do you calculate heart rate from an ECG
300/number of large squares between beat (R-R intervals)
88
what time does a big box on an ECG represent
0.2 seconds
89
what time does a small box on an ECG represent
0.04 seconds
90
what in the ECG rhythm strip
prolonged recording of one lead (usually lead 2) which allows you to detect rhythm disturbance
91
what reasons (3) show the need for 12 leads
- 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
what are the 6 key steps in analysing an ECG
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
what 7 questions do you ask yourself to workout rhythm
``` 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
how many small squares should the PR interval be
3-5 small/ 1 big
95
what are three heart diseases which have a normal resting ECG
myocardial infarction (may or may not have ECG changes). intermittent rhythm disturbance, stable angina (do exercise ECG)
96
how long is each small square
0.04 seconds
97
how long is each big square
0.2 seconds
98
how do you calculate the heart rate when its irregular
count number or QRS complexes in 30 big squares and times by 10
99
what leads are inferior and what coronary artery is this
II, III, aVF right coronary artery
100
what leads are anterior and what coronary artery is this
V1-4 left anterior descending
101
what leads are lateral and what coronary artery is this
I, V5-6 circumflex
102
how is right axis deviation shown on an ECG
lead I down, lead aVF up
103
how is left axis deviation shown on an ECG
lead I up, lead aVF down
104
how long is the PR interval usually
bigger than 3 small, smaller than 1 big
105
what are the 6 steps in reading an ECG
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
when is ST elevation significant
when at least 2mm in 2 adjacent chest leads or 1mm in limb leads
107
what does no P waves and irregularity mean on an ECG
A fib
108
what does tall QRS's in V4, 5 and 6 mean
LVH
109
what leads show anteroseptal
V1-4
110
what leads show anterolateral
I, aVL, V1-6
111
which coronary artery is usually affected in an inferior MI
right coronary
112
what coronary artery is usually affected in an anterior MI
left coronary

Cardiovascular (34 decks)

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