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brs (phase 1b) > (cardioresp) electrocardiography & rhythm disorders > Flashcards

(cardioresp) electrocardiography & rhythm disorders Flashcards

1
Q

what is the clinical relevance of the ECG?

A

helps to identify conduction abnormalities, structural abnormalities and perfusion abnormalities

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2
Q

what are the advantages of ECGs?

A

relatively cheap and easy to undertake

reproducible between people and centres and over time

quick turnaround on results and reports

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3
Q

what are the components to an ECG?

A

electrodes (stick onto skin directly)

cables/wires (connect to electrodes)

leads (results - representation of electrical activity from a specific perspective)

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4
Q

what are the electrodes in an ECG?

A

small, conductive patches that stick to the skin and are placed at certain spots on the limbs to record electrical activity

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5
Q

what are the leads in an ECG?

A

an ECG lead is a graphical representation of the heart’s electrical activity which is calculated by analysing data from several ECG electrodes.

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6
Q

what are the cables/wires in an ECG?

A

cables/wires connect the electrodes on the skin surface to the ECG machine

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7
Q

how many electrodes, cables and leads are present in an ECG?

A

10 electrodes
10 cables/wires
12 leads

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8
Q

why is an ECG important?

A

used to record the electrical activity of the heart from different angles to both identify and locate pathology

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9
Q

what is a vector?

A

a quantity that has both magnitude and direction

typically represented by an arrow in the net direction of movement, whose size reflected the magnitude of the vector

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10
Q

how is a vector respresented?

A

typically represented by an arrow in the net direction of movement, whose size reflected the magnitude of the vector

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11
Q

which electrode are upward deflections towards?

A

positive electrode

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12
Q

which electrode are downward deflections towards?

A

negative electrode

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13
Q

what does the steepness of the vector line denote?

A

the velocity of the action potential

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14
Q

what does the width of the vector line denote?

A

the duration of the event

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15
Q

what does an isoelectric line represent?

A

no net change in voltage = no depolarisation occuring

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16
Q

what does an isoelectric line look like?

A

vectors are perpendicular to the lead

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17
Q

describe the electrical conduction pathway within the heart

A

sinoatrial node

(via internodal tracts)

atrioventricular node

(via bundle of His)

branched bundles (i.e left and right bundle branches)

Purkinje fibres

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18
Q

when does the line deflect downwards on an ECG?

A

wave of depolarisation moving towards –ve from +ve

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19
Q

when does the line deflect upwards on an ECG?

A

wave of depolarisation moving towards +ve from -ve

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20
Q

what are the letter components of an ECG?

A

P, Q, R, S and T

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21
Q

what is a P wave?

A

the electrical signal that stimulates atrial depolarisation, preceding contraction of the atria (atrial systole) = a few milliseconds apart

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22
Q

what is the QRS complex?

A

the electrical signal that stimulates ventricular depolarisation, preceding contraction of the ventricles (ventricular systole) = a few milliseconds apart

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23
Q

what is a T wave?

A

the electrical signal that stimulates ventricular repolarisation, preceding relaxation of the ventricles (ventricular diastole) = a few milliseconds apart

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24
Q

what does the QRS complex precede?

A

ventricular contraction = occurs a few milliseconds after

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25
Q

how is atrial systole shown on an ECG?

A

P wave

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26
Q

how is ventricular systole systole shown on an ECG?

A

QRS complex

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27
Q

how is ventricular diastole shown on an ECG?

A

T wave

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28
Q

when does the electrical activity occur in comparison to the mechanical contraction?

A

electrical activity precedes the myocardial contraction (mechanical activity) = a few milliseconds apart

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29
Q

what is the function of the sinoatrial node?

A

stimulates atrial depolarisation

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30
Q

what does the sinoatrial node consist of?

A

autorhythmic myocytes

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31
Q

what are autorhythmic myocytes?

A

self‐excitable cells that are able to generate an action potential without external stimulation by nerve cells

e.g. SAN, AVN, Purkinje fibres

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32
Q

what is the function of the atrioventricular node and why is this important?

A

‘electrical gatekeeper; between the atria and ventricles’

to delay the conduction of the wave of depolarisation from the SAN

= delay allowing for proper atrial contraction AND efficient ventricular filling

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33
Q

what is the sinoatrial node linked to on an ECG?

A

P wave

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34
Q

what is the atrioventricular node linked to on an ECG?

A

isoelectric on an ECG (as no depolarisation BUT slows down the conduction of the wave of depolarisation)

= allow sufficient time for complete atrial contraction AND efficient ventricular filling

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35
Q

how does the speed of conduction change from the SAN to the AVN?

A

slower signal transduction than at SAN

= delay introduced allows sufficient time for ventricular filling

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36
Q

how does the speed of conduction change from the AVN to the Bundle of His?

A

goes back to rapid conduction (more rapid than SAN)

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37
Q

how is the Bundle of His adapted for rapid conduction?

A

insulated

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38
Q

what are the bundle branches responsible for?

A

septal depolarisation

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39
Q

what are the Purkinje fibres responsible for?

A

ventricular depolarisation

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40
Q

what part of an ECG are Purkinje fibres linked to?

A

QRS complex

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41
Q

what do fully depolarised ventricles look like on an ECG?

A

isoelectric on an ECG

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42
Q

what does ventricular repolarisation look like on an ECG?

A

T wave

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43
Q

explain why there is a dip from the isoelectric line to point Q during septal depolarisation

A

septal depolarisation occurs from left-to-right depolarisation of the interventricular septum

= opposite to the direction of the electrode
(BUT only minor negative deflection)

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44
Q

what are the three types of leads in ECG?

A

chest leads (unipolar)

limb leads (bipolar)

augmented limb leads (unipolar)

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45
Q

list the leads that make up a 12-lead ECG

A

unipolar chest leads
V1
V2
V3
V4
V5
V6

unipolar augmented limb leads
aVR
aVL
aVF

bipolar limb leads
lead I
lead II
lead III

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46
Q

name the bipolar leads and describe their placement

A

bipolar limb leads

lead I = right arm to left arm
lead II = right arm to left leg
lead III = left arm to left leg

(rule of Ls)

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47
Q

name the chest leads and describe their placement

A

unipolar chest leads

V1 = 4th ICS, right sternal border
V2 = 4th ICS, left sternal border
V3 = halfway between V2 and V4
V4 = 5th ICS, mid-clavicular line
V5 = 5th ICS, anterior axillary line
V6 = 5th ICS, mid-axillary line
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48
Q

name the augmented leads and describe their placement

A

unipolar augmented limb leads

aVR (augmented Vector Right) = +ve electrode on right shoulder

aVL (augmented Vector Left) = +ve electrode on left shoulder

aVF (augmented Vector Foot) = +ve electrode on (left) foot

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49
Q

name the unipolar leads and explain why they are called so

A
  • unipolar chest leads: V1-V6
  • unipolar augmented leads: avf, aVR, aVL

called unipolar because they only assess the signal at one electrode

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50
Q

name the bipolar leads and explain why they are called so

A
  • bipolar limb leads: lead I-III

called bipolar because they compare the signals at two electrodes

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51
Q

where is V1 placed and what colour is associated with it most commonly?

A

4th ICS, right sternal border

red

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52
Q

where is V2 placed and what colour is associated with it most commonly?

A

4th ICS, left sternal border

yellow

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53
Q

where is V3 placed and what colour is associated with it most commonly?

A

5th ICS, between V2 and V4

green

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54
Q

where is V4 placed and what colour is associated with it most commonly?

A

5th ICS, mid-clavicular line

brown

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55
Q

where is V5 placed and what colour is associated with it most commonly?

A

5th ICS, anterior axillary line

black

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56
Q

where is V6 placed and what colour is associated with it most commonly?

A

5th ICS, mid-axillary line

purple

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57
Q

where is RA placed and what colour is associated with it most commonly?

A

either on the right shoulder or right wrist

(wrist/shoulder consistent w left side)

red

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58
Q

where is LA placed and what colour is associated with it most commonly?

A

either on the left shoulder or left wrist

(wrist/shoulder consistent w right side)

yellow

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59
Q

where is RL placed and what colour is associated with it most commonly?

A

either on the right thigh or right ankle

(thigh/ankle consistent w left side tho)

black

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60
Q

where is LL placed and what colour is associated with it most commonly?

A

either on the left thigh or left ankle

(thigh/ankle consistent w right side tho)

green

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61
Q

what information can you see on this ECG?

A

(should have patient info)

bottom

  • date and time ECG taken
  • where it was done
  • rate of the paper = 25mm/sec (common)
  • amplitude/voltage = 10mm/mV

each lead
- labels of all twelve leads (all look at the heart in diff way/diff perspective = diff waves)

upper

  • heart rate calculated
  • loads of intervals worked out
  • axis worked out
  • key voltages in diff leads
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62
Q

why is the normal, most common rate of ECG paper?

A

normally 25mm/second but can differ rarely (so must check!)

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63
Q

what must you remember about the limb leads when taking an ECG?

A

always pair wrist placement with ankle placement

always pair shoulder placement with thigh placement

(cannot do wrist and thigh - bit random :/ as well as shoulder and ankle)

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64
Q

what is the length of a small square on ECG paper?

(x axis)

A

0.04 seconds = 40 milliseconds (!)

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65
Q

what is the length of a large square on ECG paper?

(x axis)

A
  1. 2 seconds (200 ms)
    (0. 04 x 5 = 0.2)
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66
Q

what is the height of a small square on ECG paper?

(y axis)

A

0.1 mV

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67
Q

what is the height of a large square on ECG paper?

(y axis)

A
  1. 5 mV
    (0. 1 x5 = 0.5)
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68
Q

what are the ECG artery territories?

A

each of the leads of the ECG (barring aVR) are associated with a region of the heart and a specific coronary artery

= tells us how effectively the cardiac muscle of that region is being perfused by that specific coronary artery

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69
Q

name the ECG artery territories

A

lateral
inferior
septal
anterior

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70
Q

which leads are septal leads?

A

V1
V2

(associated with the LAD artery)

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71
Q

which leads are anterior leads?

A

V3
V4

(associated with the LAD)

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72
Q

which leads are lateral leads?

A

V5
V6
lead I
avL

(associated with the LCx artery)

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73
Q

which leads are inferior leads?

A

lead II
lead III
aVF

(associated with the RCA)

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74
Q

which coronary artery are the septal leads associated with?

A

left anterior descending (LAD)

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75
Q

which coronary artery are the anterior leads associated with?

A

left anterior descending (LAD)

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76
Q

which coronary artery are the lateral leads associated with?

A

left circumflex artery (LCx)

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77
Q

which coronary artery are the inferior leads associated with?

A

right coronary artery (RCA)

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78
Q

what is the rhythm strip and why is it important?

A

to assess the cardiac rhythm accurately, a prolonged recording from one lead is used to provide a rhythm strip

= lead II, which usually gives a good view of the P wave, is most commonly used to record the rhythm strip

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79
Q

how long are most leads time-wise on an ECG?

A

approx 2.5 seconds

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80
Q

how long is the rhythm strip time-wise on an ECG?

A

approx 10 seconds (usually of lead II)

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81
Q

which lead is most commonly used as the rhythm strip and why?

A

lead II - as it usually gives a good view of the P wave

82
Q

what does ST elevation in leads II, III and aVF indicate?

A

obstruction of the RCA

83
Q

summarise the

  • location (chest/limb)
  • polarity
  • plane (coronal/horizontal)
  • +ve electrode
  • view (S/A/L/I)
  • artery

of each of the leads in a 12-lead ECG

A
84
Q

how many milliseconds make a second?

A

100ms = 1 second

(so 0.04s of a small ECG square 40ms)

85
Q

name the intervals commonly calculated from an ECG

A

single wave calculations:
P-R interval
Q-T interval
S-T interval

adjacent wave calculations:
R-R interval

86
Q

name the durations commonly calculated from an ECG

A

P wave duration
QRS complex duration
T wave duration

87
Q

differentiate between a P-R interval and a P-R segment

A

a P-R interval = time from the onset of the P wave to the start of the QRS complex

a P-R segment = flat, usually isoelectric segment between end of the P wave and the start of the QRS complex

88
Q

differentiate between an S-T interval and an S-T segment

A

an S-T interval = time from the end of the QRS complex to the end of the T wave

an S-T segment = flat, usually isoelectric segment between end of the QRS complex and the start of the T wave

89
Q

label the segments, intervals, and waves on the following ECG

A
90
Q

how is heart rate calculated from an ECG?

A

method 1: 300/number of large squares

method 2: 60,000/(40 x number of small squares)

91
Q

what is the direction of lead I?

A

from the RA (-ve) to the LA (+ve)

92
Q

what is the direction of lead II?

A

from the RA (-ve) to the LL (+ve)

93
Q

what is the direction of lead III?

A

from LA (-ve) to the LL (+ve)

94
Q

what is the direction of aVR?

A

from lead III (-ve) to the RA (+ve)

95
Q

what is the direction of lead aVL?

A

from lead II (-ve) to the LA (+ve)

96
Q

what is the direction of lead aVF?

A

from lead I (-ve) to the LL (+ve)

97
Q

what is cardiac axis?

A

gives us an idea of the overall direction of electrical activity

= average direction of ventricular depolarisation during ventricular contraction

98
Q

how is the cardiac axis calculated using exact calculations?

A
99
Q

how else can this cardiac axis be worked out?

A
100
Q

what must you do before interpreting an ECG?

A

always verify voltage = 10mm/mV and paper speed = 25mm/s

(!!! - very standardised but still)

101
Q

what are the steps to analysing ECGs?

A

step 1 = rate & rhythm

step 2 = P wave duration, P-R interval

step 3 = QRS duration

step 4 = QRS axis

step 5 = S-T segment

(step 6 = Q-T interval)
(step 7 = T wave)

102
Q

what is the normal QRS axis?

A

normal axis deviation = -30 ro 90 degrees

103
Q

summarise how ECGs are reported

A
104
Q

interpret the following ECG and explain your reasoning

A

sinus rhythm

  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and normal (83 bpm)
  • otherwise unremarkable
105
Q

what are the characteristic features of sinus rhythm on an ECG?

A
  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and normal
  • otherwise unremarkable
106
Q

what is a normal heart rate?

A

60-100 bpm

107
Q

interpret the following ECG and explain your reasoning

A

sinus bradycardia

  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and SLOW (56 bpm)
108
Q

what are the characteristic features of sinus bradycardia on an ECG?

A
  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and SLOW (56 bpm)
109
Q

what can sinus bradycardia be caused by?

A

can be caused by medication or vagal stimulation

= can be healthy, not always pathological!

110
Q

interpret the following ECG and explain your reasoning

A

sinus tachycardia

  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and FAST (107 bpm)
111
Q

what can sinus tachycardia be caused by?

A

most often a physiological response to something (i.e. secondary)

112
Q

what are sinus waves and what are the ‘types’?

A

normal rhythm waves
= sinus rhythm, sinus bradycardia, sinus tachycardia

!! each P wave is followed by a QRS complex (1:1) !!

113
Q

interpret the following ECG and explain your reasoning

A

sinus arrhythmia

  • each P wave is followed by a QRS complex (1:1)
  • rate is IRREGULAR (variable R-R intervals) and normal-ish (65-100 bpm)
114
Q

why are the R-R intervals so erratic in this ECG?

A

varies with breathing cycle

= irregular breathing, irregular R-R intervals

115
Q

what indicates a normal rate?

A

approx 60-100 bpm

116
Q

what indicates normal rhythm?

A

even R-R intervals

117
Q

what indicates irregular rhythm?

A

variable R-R intervals

118
Q

what are the characteristic features of sinus tachycardia on an ECG?

A
  • each P wave is followed by a QRS complex (1:1)
  • rate is regular (even R-R intervals) and FAST (107 bpm)
119
Q

what are the characteristic features of sinus arrhythmia on an ECG?

A
  • each P wave is followed by a QRS complex (1:1)
  • rate is IRREGULAR (variable R-R intervals) and normal-ish (65-100 bpm)
120
Q

what usually slows down heart rate to within the expected interval?

A

vagal parasympathetic stimulation

121
Q

interpret the following ECG and explain your reasoning

A

atrial fibrillation

  • oscillating baseline, not exactly flat and isoelectric (atria contracting asynchronously)
  • rhythm can be irregular and rate can be variable and slower than normal
122
Q

why does the baseline oscillate in atrial fibrillation on an ECG?

A

the atria are contracting asynchronously (i.e. haphazardly)

= turbulent flow
= increases clot risk (so patient may be on warfarin)

123
Q

what is the impact of the asynchronous contraction of the atria in atrial fibrillation?

A

results in turbulent flow
= increased risk of clot formation

124
Q

how is the increased risk of clot formation mitigated in atrial fibrillation?

A

patient likely to be prescribed warfarin

125
Q

what are the characteristic features of atrial fibrillation on an ECG?

A
  • oscillating baseline (as atria are contracting asynchronously)
  • rhythm may be irregular and rate may be slow
126
Q

interpret the following ECG and explain your reasoning

A

atrial flutter

  • regular ‘saw-tooth’ pattern in baseline (lead II, lead III, aVF) - not always visible in all leads
  • atrial to ventricular beats are a 2:1, 3:1 ratio or higher
127
Q

what are the characteristic features of atrial flutter on an ECG?

A
  • regular ‘saw-tooth’ pattern in baseline (lead II, lead III, aVF) - not always visible in all leads
  • atrial to ventricular beats are a 2:1, 3:1 ratio or higher
128
Q

where is the ‘saw-tooth’ pattern seen in an atrial flutter ECG?

A

usually seen in lead II, lead III and aVF (inferior leads)

= not always seen in every lead (!!)

129
Q

describe the ratio of atrial to ventricular contraction in atrial flutter on an ECG?

A

atrial to ventricular beats at a 2:1 ratio, 3:1 ratio, or higher

130
Q

interpret the following ECG and explain your reasoning

A

first degree heart block

  • prolonged PR segment/interval caused by slower AVN conduction
  • regular rhythm
  • 1:1 ratio of P waves to QRS complexes
131
Q

what are the characteristic features of first-degree heart block?

A
  • prolonged PR segment/interval caused by slower AVN conduction
  • regular rhythm
  • 1:1 ratio of P waves to QRS complexes
132
Q

how does first-degree heart block compare to other degrees of heart block?

A

most benign form of heart block

usually a progressive disease of ageing

133
Q

(briefly) explain the pathophysiology of first-degree heart block

(link to features on an ECG)

A
  • AVN takes longer to conduct signal = elongated P-R segment/interval
  • conduction system is functional = all P waves result in QRS complexes (1:1 ratio)
134
Q

what are the two types of second-degree heart block?

A

Mobitz I
Mobitz II

135
Q

interpret the following ECG and explain your reasoning

A

second-degree heart block (mobitz I)

  • gradual prolongation of the PR interval until beat skipped
  • most P-waves are followed by QRS; but some P-waves are not
  • regularly irregular (caused by a diseaed AV node)
136
Q

what are the characteristic features of second-degree heart block (Mobitz I)?

A
  • gradual prolongation of the PR interval until beat skipped (QRS dropped)
  • most P-waves are followed by QRS; but some P-waves are not
  • regularly irregular (caused by a diseased AV node)
137
Q

what is Mobitz I second-degree heart block also called?

A

Wenkebach’s block

138
Q

(briefly) explain the pathophysiology of second-degree heart block (Mobitz I)

(link to features on an ECG)

A

varying failure of conduction through the diseased AVN occurs = some P waves may not be followed by a QRS complex

(i.e. the 1:1 P:QRS ratio maintained in first-degree heart block no longer is)

139
Q

interpret the following ECG and explain your reasoning

A

second degree heart block (Mobitz II)

  • regular P waves but only some are followed by QRS complexes
  • no P-R prolongation
  • regularly irregular: successes to failures (e.g. 2:1) or random
140
Q

what are the characteristic features of second-degree heart block (Mobitz II)?

A

refers to periodic atrioventricular block with constant PR intervals in the conducted beats

  • regular P waves but only some are followed by QRS complexes
  • no P-R prolongation
  • regularly irregular: successes to failures (e.g. 2:1) or random
141
Q

(briefly) explain the pathophysiology of second-degree heart block (Mobitz II)

(link to features on an ECG)

A

the AVN becomes periodically blocked but when it is not, there are regular P waves and P-R intervals

142
Q

what must you remember about all kinds of heart block?

A

can rapidly deteriorate into the next degree of heart block

143
Q

differentiate between the two types of second-degree heart block

A

Mobitz I (Wenkebach) = gradual prolongation of the P-R interval until a subsequent QRS complex in dropped (conduction through the AVN does occur but can at times be impaired)

Mobitz II = refers to periodic atrioventricular block with constant PR intervals in the conducted beats

144
Q

what happens if second degree Mobitz II heart block is left untreated?

A

will rapidly progress onto third degree heart block

145
Q

interpret the following ECG and explain your reasoning

A

third-degree heart block (complete)

  • all P-waves are regular, QRS complexes are regular, but no relationship
  • P waves can be hidden within bigger vectors
  • non-sinus rhythm (require back-up pacemaker cells = i.e. ventricle tries to compensate)
146
Q

what are the characteristic features of third-degree heart block?

A
  • all P-waves are regular, QRS complexes are regular, but no relationship
  • P waves can be hidden within bigger vectors
  • non-sinus rhythm (require back-up pacemaker cells = i.e. ventricle tries to compensate)
147
Q

(briefly) explain the pathophysiology of third-degree heart block

(link to features on an ECG)

A

the electrical signal from the atria to the ventricles is completely blocked

= ventricle usually starts to beat on its own acting as a substitute pacemaker but the heartbeat is slower and often irregular and not reliable

148
Q

third-degree heart block presents with a non-sinus rhythm - explain what this is and how this is overcome :)

A

abnormal rhythm of the heart where electrical stimuli are not always initiated properly in the SA node and may not follow the normal conduction pathway in the heart

= the ventricular cells (blocked from atrial SAN communication will begin to act as their own pacemaker cells)

149
Q

what is the implication of third-degree heart block?

A

as non-sinus rhythm occurs due to complete blockage between the atria and the ventricles

= alternative cells need to act as pacemaker cells (in this case, ventricular myocytes)

150
Q

differentiate between the pathophysiology of the three types of heart block

A

first-degree = conduction through the AVN is slowed and impaired but not stopped (i.e. conduction system is still intact)

second-degree (Mobitz I) = conduction is slowed through the AVN node but can sometimes be completely stopped (but often returns to conduction)

second-degree (Mobitz II) = periodic atrioventricular block with constant PR intervals in the conducted beats

third-degree = complete block of the electrical signal from the atria to the ventricles

151
Q

differentiate between the presentation of the three types of heart block on an ECG

A

first-degree = elongated P-R intervals

second-degree (Mobitz I) = gradual elongation of P-R intervals until beat skipped

second-degree (Mobitz II) = normal ECG except some P waves may not be followed by QRS complexes

third-degree = regular P waves and regular QRS complexes but no relationship between the two

152
Q

interpret the following ECG and explain your reasoning

A

ventricular tachycardia

  • P-waves hidden within QRS complexes so cannot see (dissociated atrial rhythm)
  • rate is regular & fast (100-200bpm)
153
Q

what are the characteristic features of ventricular tachycardia?

A
  • P-waves hidden within QRS complexes so cannot see (dissociated atrial rhythm)
  • rate is regular & fast (100-200bpm)
    (- even though rhythm is very fast, it is still functional)
154
Q

what must you remember about ventricular tachycardia?

A

shockable rhythm (!!!!!!!) = defibrillators widely available

if not acted on swiftly, can risk deterioration into ventricular fibrillation (cardiac arrest)

155
Q

what does ventricular tachycardia risk if it is not addressed immediately?

A
  • at high risk of deteriorating into fibrillation (cardiac arrest)
156
Q

how do P waves appear in ventricular tachycardia?

A

hidden within the QRS complexes, not very pronounced/distinguishable

157
Q

why must you shock a patient who has ventricular tachycardia?

A

v tach = poorly perfusing rhythm and patients may present with or without a pulse

so to regulate rhythm and allow the SAN to overtake as the primary pacemaker cells

158
Q

interpret the following ECG and explain your reasoning

A

ventricular fibrillation

  • heart rate irregular and 250 bpm and above
  • heart unable to generate an output
  • shockable rhythm – defibrillators widely available
159
Q

what are the characteristic features of ventricular fibrillation?

A
  • heart rate irregular and 250 bpm and above
  • heart unable to generate an output
  • shockable rhythm – defibrillators widely available
160
Q

differentiate between ventricular tachycardia and ventricular fibrillation

A

tachycardia

  • still likely to have some cardiac output, but very fast rhythm that needs to be defibrillated back to normal
  • 100-200 bpm (regular)

fibrillation

  • extremely fast rhythm so ventricular filling does not properly occur before contraction so no blood is being pumped out
  • above 250 bpm (irregular)

(both are shockable rhythms!)

161
Q

why can a cardiac output not be generated properly in ventricular fibrillation?

A

heart rate is very very fast and very irregular

= no time for proper ventricular filling before the ventricles contract so sometimes, no blood is pumped out (!!!!!)

162
Q

name the two shockable rhythms

A

ventricular tachycardia

ventricular fibrillation

163
Q

interpret the following ECG and explain your reasoning

A

ST elevation

  • P waves visible and always followed by QRS (1:1)
  • rhythm is regular and rate is normal (85 bpm)
  • ST-segment is elevated >2mm above the isoelectric line
164
Q

what are the characteristic features of ST elevation?

A
  • P waves visible and always followed by QRS (1:1)
  • rhythm is regular and rate is normal (85 bpm)
  • ST-segment is elevated >2mm above the isoelectric line
165
Q

what is ST elevation?

A

when the ST-segment is elevated >2mm above the isoelectric line

166
Q

what causes ST elevation?

A

caused by infarction (tissue death caused by hypoperfusion)

= infarcted myocardium leads to muscle death

167
Q

interpret the following ECG and explain your reasoning

A

ST depression

  • P waves visible and always followed by QRS
  • rhythm is regular and rate is normal (95 bpm)
  • ST-segment is depressed >2mm below the isoelectric line
168
Q

what are the characteristic features of ST depression?

A
  • P waves visible and always followed by QRS
  • rhythm is regular and rate is normal (95 bpm)
  • ST-segment is depressed >2mm below the isoelectric line
169
Q

what is ST depression?

A

when the ST-segment is depressed >2mm below the isoelectric line

170
Q

what causes ST depression?

A

caused by myocardial ischaemia (coronary insufficiency)

= reduction in the oxygen supply causing slower damage

171
Q

differentiate between ST elevation and ST depression

A

ECG

  • while ST elevation is when the ST segment is >2 mm above the isoelectric line
  • ST depression is when the ST segment is <2 mm below the isoelectric line

pathophysiology

  • ST elevation is caused by myocardial infarction (muscular blood supply completely lost)
  • ST depression is caused by myocardial ischaemia (muscular blood supply significantly reduced, but not lost)
172
Q

what is the key feature of atrial fibrillation on an ECG?

A

oscillating baseline

(high risk of clots managed with oral anticoagulation)

173
Q

what is the key feature of atrial flutter on an ECG?

A

sawtooth pattern

often occurring in a 2:1 or 3:1 ratio of P to QRS

174
Q

what is the key feature of first-degree heart block on an ECG?

A

PR interval longer than normal, due to slower conduction

175
Q

what is the key feature of second-degree (Mobitz I) heart block on an ECG?

A

PR interval gradually elongates until a beat is missed

176
Q

what is the key feature of second-degree (Mobitz II) heart block on an ECG?

A

P waves are regular, but some beats not conducted (e.g. 2:1 is two beats conducted then one missed)

177
Q

what is the key feature of third-degree heart block on an ECG?

A

atria and ventricles beat asynchronously – HR at non-sinus rhythm

178
Q

what is the key feature of ventricular tachycardia on an ECG?

A

very fast ventricular rate, can rapidly progress and needs defibrillation

179
Q

what is the key feature of ventricular fibrillation on an ECG?

A

cardiac arrest; asynchronous ventricular contract, no output, needs defibrillation

180
Q

what is the key feature of ST elevation and depression on an ECG?

A

>2 mm baseline deviation up or down indicates infarction or ischaemia, respectively

181
Q

what is cardiac arrest alternatively known as?

A

ventricular fibrillation

182
Q

what does the following ECG show? explain your reasoning

A

second degree heart block (Mobitz II)

= P-R interval elongates gradually until for one of the waves the QRS complex is dropped

183
Q

what does the following ECG show? explain your reasoning

A

sinus rhythm

= regular rate; regular rhythm + every P wave is followed by a QRS (1:1)

184
Q

what does the following ECG show? explain your reasoning

A

ventricular tachycardia

= P waves are hidden in the QRS complex; rate is regular & fast

185
Q

what does the following ECG show? explain your reasoning

A

first-degree heart block

= prolonged P-R interval (!!!)

= regular rate and rhythm

= P waves are followed by QRS complexes (1:1)

186
Q

what does the following ECG show?

explain your answer

A

sinus tachycardia

= rate increased, rhythm regular

= normal P:QRS ratio of 1:1

187
Q

what does the following ECG show?

explain your answer

A

ST depression

= the ST segment is depressed >2mm below the isoelectric line

= regular rate and rhythm + normal P:QRS ratio

188
Q

what does the following ECG show?

explain your answer

A

atrial flutter

= classic ‘saw-tooth’ baseline pattern (in II, III, avF)

= atrial:ventricular beats are 2:1/3:1

189
Q

what does the following ECG show?

explain your answer

A

ventricular fibrillation

= very irregular rate and rhythm

190
Q

what does the following ECG show?

explain your answer

A

sinus bradycardia

= rate reduced, rhythm normal

= normal P:QRS ratio

191
Q

what does the following ECG show?

explain your answer

A

third-degree (complete) heart block

= regular P waves, regular QRS complexes but no relationship bw them (i.e. non-sinus rhythm)

192
Q

what does the following ECG show?

explain your answer

A

sinus arrhythmia

= normal P:QRS complex ratio BUR rate is very irregular, yet usually normal

193
Q

what does the following ECG show?

explain your answer

A

ST-elevation

= normal P:QRS, normal rate and rhythm

= BUT the ST segment is elevated >2mm above the isoelectric line

194
Q

what does the following ECG show?

explain your answer

A

second-degree heart block (Mobitz I) - Wenkebach

= gradual prolongation of the P-R interval until eventually the subsequent QRS after a P wave is dropped

195
Q

what does the following ECG show?

explain your answer

A

atrial fibrillation

= oscillating baseline

= may have an irregular rhythm

196
Q

what does the PR interval represent?

A

the time between atrial depolarization and ventricular depolarization

197
Q

what does the PR segment represent?

A

the time delay between atrial and ventricular depolarisation

198
Q

what does the QT interval represent?

A

the time from the beginning of ventricular depolarisation to the end of ventricular repolarisation

199
Q

what does the ST segment represent?

A

the interval between the end of ventricular depolarization (QRS complex) and the beginning of repolarization (T wave)

200
Q

differentiate between the PR interval and the PR segment

A

while the PR interval takes the P wave into account, the PR segment occurs from the end of the P wave to the peak of the QRS complex

PR interval = time from atrial depolarisation to ventricular depolarisation

PR segment = the time delay in the conduction of the electrical impulse as it travels through the AVN

brs (phase 1b) (71 decks)

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