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20005 > ecg > Flashcards

ecg Flashcards

1
Q

what do the axis of an ecg show

A
  • vertical is voltage
  • horizontal is time
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2
Q

what is hypertrophy

A

when one side of the heart is larger than the other

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3
Q

what is on the vertical axis of an ecg

A
  • voltage, in mV
  • the higher the voltage the more that is drawn to this side of the heart
  • suggest hypertrophy if big
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4
Q

what is shown on the horizontal axis of an ecg

A
  • time, in milliseconds and seconds
  • longer time shows a blockage in the normal electrical circuit
  • increased time suggests heart damage
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5
Q

what are the different limb leads

A

aVL, Lead I, II, III, aVF, aVR

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6
Q

what are the different chest leads

A

V1, V2, V3, V4, V5, V6

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7
Q

what are the different views of limb leads

A
  • lateral
  • inferior
  • right
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8
Q

what are the different views of the chest lead

A
  • septal
  • anterior
  • lateral
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9
Q

which leads show a lateral view

A

aVL, lead I and lead II

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10
Q

which leads show an inferior view

A

lead II, lead III and aVF

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11
Q

which leads show the right view

A

aVR

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12
Q

which leads show a septal view

A

V1 and V2

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13
Q

which leads show an anterior view

A

V2, V3 and V4

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14
Q

which leads show a lateral view

A

V5 and V6

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15
Q

what does the septal ecg view show

A

the middle section of the heart

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16
Q

what does the anterior ecg view show

A

the main functioning wall of the heat

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17
Q

what is einthovens triangle

A

the net current of 2 limb leads

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18
Q

what view does aVL give

A

view of the heart from the left shoulder

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19
Q

what view does aVR give

A

view of the heart from the right shoulder

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20
Q

what view does aVF give

A

view of the heart from the foot looking up form the bottom

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21
Q

what view does lead I give

A

right arm to left arm

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22
Q

what view does lead II give

A

right arm to left leg

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23
Q

what view does lead III give

A

left arm to left leg

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24
Q

what is the path of conduction in the heart

A
  1. SA node fires to the AV node
  2. AV node then fires to bundle of his
  3. bundle of his signalling is sent down the heart septum and up the pirkinje fibres
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25
Q

what do the different ecg waves represent in conduction

A
  • P wave in SAN to AVN firing
  • Gap is the space between the AV and bundle of his firing
  • QRS is the bundle branches down to the purkinje fibres
  • T wave is relaxation
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26
Q

what are the 4 different cardiomyocytes

A
  • intercalated discs
  • desmosomes
  • gap junctions
  • contraction
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27
Q

what are desmones

A

scaffolding that holds everything together

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28
Q

what are gap junctions

A

water permeable junctions that allows sodium to leave through pours. when sodium leaves so does potassium

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29
Q

what are the contraction cardiomyocytes

A

the action potentials in the heart

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30
Q

what is the trigger for action potentials

A

a change in the voltage across membranes at -70mV

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31
Q

what do the pacemaker cardiomyocytes do

A
  • they innate automatically without outside influence
  • SAN - 60-90bpm
  • AVN - 40-60bpm
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32
Q

what are the 2 phases of pacemaker cardiomyocytes

A
  • phase 0, the climb phase
  • phage 3, the plummet
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33
Q

what occurs in phase 0/ climb

A
  • depolarisation
  • calcium ion channels opens and calcium enters the cell making it more positive (upping the mV)
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34
Q

what occurs in phase 3/ plummet

A
  • full repolarisation
  • the potassium channels open and leave the cell causing full relaxation
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35
Q

what do the non-pacemaker cardiomyocytes do

A
  • contractile muscle cells in the atria and ventricles
  • do not generate spontaneous action potentials
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36
Q

what is the mV for resting membrane potential

A

-90mV

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37
Q

what is the mV for action potential trigger

A

-70mV

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38
Q

what are the stages of non-pacemaker cardiomyocytes

A
  • summit/0
  • plummet/1
  • continue/2
  • plummet/3
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39
Q

what happens in phase 0 of non pacemaker cardiomyocytes

A
  • depolarisation
  • sodium ion channels enter and sodium enters the cell making it more positive
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40
Q

what happens in phase 1 of non-pacemaker cardiomyocytes

A
  • slight repolarisation
  • potassium channels open and potassium leaves the cell making it more negative
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41
Q

what happens in phase 2 of non pacemaker cardiomyocytes

A
  • slight repolarisation
  • L type calcium channels open and calcium enters the cell and there is full contraction
42
Q

what happens in phase 3 of non-pacemaker cardiomyocytes

A
  • full repolarisation
  • potassium ion channels open and potassium leaves the cells causing full relaxation
43
Q

what is contraction-coupling

A

all cardiomyocytes are electrically couples and have gap junctions that link opposite cells to allow electrical activity to pass through

44
Q

what are some accessory pathways in contraction couplin

A
  • atriofascicular - RA to RBB
  • atrio-Hisian - atrium to His
  • nodofascicular - AV to RBB
  • nodoventricular - AV to RV
  • fasciculoventricular - His to ventricles
45
Q

which axis show positive deflection in cardiac axis

A

lead II, I and aVF

46
Q

which axis shows negative deflections in cardiac axis

A

aVR

47
Q

which axis shows biphasic deflection

A
  • lead III and aVL
  • which one is more positive says the way the signal is travelling from
  • if bigger it shows where the signal is being pulled from
48
Q

what does a positive deflection show

A

signal towards the lead

49
Q

what does negative deflection show

A

signal away from the lead

50
Q

what does biphasic deflection show

A

signal perpendicular to the lead

51
Q

what is right axis deviation

A

when depolarisation is being pulled to the right side of the heart
- increases positive deflection in lead III and negative deflection in aVL

52
Q

what is left axis deviation

A

when depolarisation is pulled to the left side of the heart
- increases negative deflection of lead III and positive deflection of aVL

53
Q

what are examples of a right axis deviation

A
  • RV hypertrophy
  • RV strain
  • lateral stemi
  • Wolff-parkinson-white
54
Q

what are examples of left axis deviation

A
  • LV hypertrophy
  • LBBB
  • inferior stemi
  • Wolff-Parkinson-White
55
Q

signs of situs inversus

A
  • lead 1 net QRS negative and P negative
  • lack of precordial R wave progression
  • mirror-image dextrocardia
56
Q

positioning of 12 lead ecg

A
  • V1 = 4th intercostal space, right sternal edge
  • V2 = 4th intercostal space, left sternal edge
  • V3 = between V2 and V4
  • V4 = 5th intercostal space, mid clavicular
  • V5 = level of V4 at anterior axillary line
  • V6 = level of V4/5 mix auxiliary line
57
Q

lead grouping on ecgs

A
  • Big LII (i,ii,iii)
  • Little LI (aVL,iii)
  • SAALL (V1,2,3,4,5,6)
58
Q

what are the main blood vessels of the heart

A
  • left anterior descending
  • proximal left anterior descending
  • left circumflex
  • right coronary artery
  • distal left anterior descending
59
Q

which vessels are blocked in an anterior STEMI

A

left anterior descending

60
Q

which vessels are blocked in a septal STEMI

A

proximal left anterior descending

61
Q

which vessels are blocked in a lateral STEMI

A

left circumflex

62
Q

which vessels are blocked in an inferior STEMI

A

right coronary artery and left circumflex

63
Q

which vessels are blocked in an apical STEMI

A

distal left anterior descending, left circumflex or right coronary artery

64
Q

which vessels are blocked in a posterior STEMI

A

right coronary artery or left circumflex

65
Q

what does a normal p wave look like

A
  • atrial depolarisation
  • <3 small squares
  • smooth hump, smaller than a t wave
  • upright in L1 and L2 and inverted in aVR, biphasic in V1
66
Q

what does a p wave look like in atrial enlargement

A
  • left - looks m shaped
  • right - looks peaked
67
Q

what should a pr interval space be

A

3-5 squares

68
Q

what does it mean when there is an change in pr interval length

A
  • > 5 squares is an AV block
  • <3 square is preexcitation/ junctional rhythm
69
Q

how should a QRS look on an ecg

A
  • normal = 3 small squares
  • narrow = <3 supraventricular origin
  • broad = >3 bundle branch block
70
Q

what is the j point

A

the interval of ventricular depolarisation and repolarisation

71
Q

what does a t wave show

A
  • repolarisation phase
  • is upright and asymmetric
72
Q

what is the QT interval

A

the period of ventricular systole from contraction to relaxation
- measured in L2 or V5-6

73
Q

changes to QT interval

A
  • prolonged is >440ms (men) or >460 (women)
  • shortened in fast HR and lengthened in slower HR
  • > 500ms can lead to torsade de points
74
Q

what causes changes in QT interval

A

either due to drug overdose or electrolyte imbalance

75
Q

what is a U wave

A
  • either: delayed purkinje fibre repolarisation, mid-myocardial repolarisation or ventricular wall after potentials
  • proceeding T waves
76
Q

what are the Chamberlin’s 10 rules

A
  1. PR interval 3-5 squares
  2. QRS complex <3 squares
  3. QRS upright in L1 and L2
  4. QRS and T waves in limb leads have same direction
  5. aVR all waves negative
  6. R waves grow V1-4 and S waves grow V1-3
  7. ST segment isoelectric in V1 and V2
  8. P waves upright in L1,2 and V2-6
  9. q waves absent or <1 square in L1,2 and V2-6
  10. T waves upright in L1,2 and V2-6
77
Q

what are atrial ectopic waves

A
  • electrical activity outside the SA node
  • P wave present but not normal
78
Q

what are ventricular ectopic waves

A
  • electrical activity outside AV node
  • broad QRS complex
  • may have atrial pre-capture
79
Q

what are Bi/Tri/Quad-rigeminy

A
  • ectopic between beats, in any rhythm
  • can trigger re-entrant tachycardia
80
Q

what is the rhythm in a first degree AV block

A

regular rhythm with a prolonged PR interval

81
Q

what is the rhythm in a second degree AV block type 2

A

irregular rhythm with a normal PR interval and a wide QRS. ratios of 2:1, 3:1, 4:1

82
Q

what is the rhythm in a second degree AV block type 1

A

an increasingly prolonged rhythm with irregular PR intervals until a QRS is dropped

83
Q

what is the rhythm in a 3rd degree AV block

A

a regular rhythm with no PR interval and P wave that are not related to the QRS complex

84
Q

what is pre-excitation

A

an accessory pathway from atria to ventricles with earlier activation then in a normal circuit

85
Q

what are different pacing spikes

A
  • vertical spike <2ms
  • atrial pace spike precedes p waves
  • ventricular pace spike precedes QRS
  • dual pace spike precedes both
86
Q

what are common pacemakers

A
  • atrial pace
  • ventricle pace
  • dual pace
87
Q

what does ST elevation show

A

ST segment shit indicating MI, caused by a coronary artery occlusion

88
Q

what does ST depression show

A

upside down ST elevation indicating ischaemia or reciprocal changes

89
Q

what happens in a right bundle branch block

A
  • delayed repolarisation of the right ventricle
  • wide QRS >120ms
  • RSR pattern in V1-3 (m shape)
  • wide S wave in V5-6 (W shape)
90
Q

what happens in a left bundle branch block

A
  • delayed depolarisation of left ventricle
  • QRS wide >120ms
  • dominant S wave V1 (W shape)
  • broad R wave V5-6 (M shape)
91
Q

what are escape rhythms

A

-when the SAN is disabled and the AV node or ventricular cells take over
- junctional escape rhythm and idioventricular escape rhythm

92
Q

what is torsades de pointes

A
  • type of polymorphic VT
  • self limits an can degenerate into VT or VF
  • crescendo and diminuendo look
93
Q

what can be seen in right ventricular hypertrophy

A
  • R:S ration >1 or R wave is >7mm in V1
  • ST depression and TWI in V1-3
94
Q

what can be seen in left ventricular hypertrophy

A
  • Sokolow Lyon criteria - s wave in V1 and R wave in V5 or V6 > 35mm
  • Modified Cornell criteria - r wave in aVL >12mm
95
Q

what are cerebral mimics

A
  • QTS prolongation and giant T wave inversion
  • caused by adrenaline surge
96
Q

what are electrical alternans

A
  • alternating beat variation
  • QRS - big, small, big, small
  • cardiac tamponade or pericardial effusion
97
Q

what causes peaked T waves

A
  • hyperkalaemia
  • the action potential duration in shortened increasing K+ channel conduction, creating excess repolarisation
98
Q

what causes prolonged PR and QT intervals

A
  • hypermagnesemia
  • AV ectopy, creating excess repolarisation
99
Q

steps for ECG interpretation

A
  1. rate
  2. rhythm
  3. axis
  4. p waves
  5. intervals
  6. qrs morphology
  7. q waves
  8. st segments
  9. t waves
100
Q
A

20005 (29 decks)

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