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Electrocardiography and Rhythm Disorders Flashcards

1
Q

What can ECGs show?

A

the electrical activity of the heart

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2
Q

What are the advantages of using an ECG?

A
  • cheap
  • reproducible
  • quick
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3
Q

What is a vector?

A

a force with both a magnitude and a direction

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4
Q

What does the isoelectric line represent?

A

no net change in voltage (of that the vector is perpendicular to the lead)

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5
Q

What does the steepness of the line show?

A

the speed of the action potential/electric conduction

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6
Q

What does the width of the wave represent?

A

the duration of the action potential

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7
Q

What does the p wave represent?

A

the signal for atrial contraction given by the SA node

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8
Q

What does the QRS complex indicate?

A

septal depolarisation, ventricular depolarisation and late ventricular depolarisation

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9
Q

What does the T wave indicate?

A

ventricular repolarisation

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10
Q

What part of the heart does the P wave represent?

A

the atria

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11
Q

what does the SA node do?

A

Auto-rhythmic myocytes that electrically signal for atrial depolarisation

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12
Q

What does the AV node do?

A
  • Slows signal conduction
  • Allows for ventricular filling
  • Protective
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13
Q

What part of an ECG represents the action of the AVN?

A

the PR segment

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14
Q

*why is there no deflections shown during the conduction by the Bundle of His?

A

Rapid, Insulated conduction that is perpendicular to the direction of the lead (therefore doesn’t show on the trace)

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15
Q

What is responsible for Q?

A

Bundle branches cause septal depolarisation

- left side is slightly less insulated, therefore the signal escapes against Lead II direction.

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16
Q

What causes an R wave?

A

Purkinje fibres causing ventricular depolarisation

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17
Q

What causes an S wave?

A

Late depolarisation of Purkinje fibres

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18
Q

What causes the T wave?

A

Ventricular repolarisation

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19
Q

What is the rule of Ls?

A

Lead I - RA > LA (one L)
Lead II - RA > LL (two Ls)
Lead III - LA > LL (three Ls)

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20
Q

What is the rule of reading ?

A

Read from Left to Right, and then Top to Bottom

The first time you come across a lead, it is negative

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21
Q

where is V1 placed?

A
  • Right of sternum

- 4th intercostal space

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22
Q

Where is V2 placed?

A
  • Left of the sternum

- 4th intercostal space

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23
Q

Where is V3 placed?

A
  • Left

- between V2 and V4

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24
Q

Where is V4 placed?

A
  • Left mid-clavicular line

- 5th intercostal space

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25
Q

Where is V5 placed ?

A
  • Left anterior axillary line

- 5th intercostal space

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26
Q

What are the 3 augmented vector lead?

A
  • Left mid axillary line

- 5th intercostal space

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27
Q

Can you shock during asystole?

A

No

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28
Q

What are the characteristics of sinus rhythm?

A
  • every P wave is followed by a QRS complex
  • regular rate (even R-R intervals)
  • normal HR (60-100bpm)
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29
Q

What causes a sinus arrhythmia?

A
  • stress
  • exercise
  • stimualtants
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30
Q

What are the characteristics of atrial fibrillation?

A
  • oscillating baseline due to asynchronous atrial contraction
  • irregular rhythm, slow rate
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31
Q

What are the characteristics of atrial flutter?

A
  • regular, saw tooth pattern in baseline

- atrial:ventricular contraction at 3:1,2:1 ratio or higher

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32
Q

What are the characteristics of a first degree heart block?

A
  • prolonged PR segment/interval caused by slower AV conduction
  • regular rhythm (1:1, P waves:QRS complexes)
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33
Q

What are the characteristics of second degree heart block (Mobitz I / Wenckebach)?

A
  • gradual prolongation of the PR interval until a beat is skipped (missing QRS complex)
  • most P waves are followed by QRS complexes, some are not
  • regularly irregular
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34
Q

What are the characteristics of second degree heart block (Mobitz II)?

A
  • regular P waves, only some are followed by a QRS complex
  • no PR elongation
  • regularly irregular (success:failure, 2:1)
  • can rapidly deteriorate into 3rd degree heart block
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35
Q

What are the characteristics of third degree (complete) heart block?

A
  • regular P waves, regular QRS complexs - BUT 0 relationship
  • P waves can be hidden in bigger vectors (QRS complexes)
  • truly non-sinus rhythm, back up pacemaker is in action
36
Q

when does something have a non-sinus rhythm?

A

when the electrical stimulation of the heart isn’t initiated by the SA node

37
Q

What are the characteristics of ventricular tachycardia?

A
  • P waves hidden - dissociated atrial rhythm
  • rate is regular and fast (100-200bpm)
  • shockable rhythm
38
Q

What are the characteristics of ventricular fibrillation?

A
  • HR is irregular and >250bpm
  • heart is unable to generate output
  • shockable rhythm
39
Q

What are the characteristics of an ST elevation?

A
  • visible P waves followed by a QRS complex (1:1)
  • regular rate and rhythm
  • ST segment is elevated >2mm above the isoelectric line
40
Q

What are the characteristics of an ST depression?

A
  • visible P waves followed by a QRS complex (1:1)
  • regular rhythm and normal rate
  • depressed >2mm below the isoelectric line
41
Q

What causes ST depression?

A

myocardial ischaemia - coronary insufficiency

42
Q

What can cause ST elevation?

A

infarction (tissue death due to hypoperfusion) - STEMI

43
Q

What risk increases when ventricular tachycardia occurs?

A

high risk of deteriorating into fibrillation (cardiac arrest)

44
Q

What causes Mobitz-1 type second degree heart block?

A

a diseased AV node

45
Q

What is first degree heart block indicative of?

A

benign, progressive disease of aging

46
Q

Where does atrial flutter tend to be seen?

A

leads II, III, and aVF

47
Q

What can be a complication associated with atrial fibrillation?

A

turbulent blood flow pattern increases the risk of clots

48
Q

What is the impact of atrial fibrillation on cardiac output?

A

minimal, as atria are not essential to the cardiac cycle

49
Q

What tends to cause sinus tachycardia?

A

often a physiological response, secondary to another factor

50
Q

What can cause sinus bradycardia?

A
  • can be normal/healthy
  • medication
  • vagal stimulation
51
Q

What are the steps of reading an ECG?

A
  • rate and rhythm
  • P wave and PR interval
  • QRS duration
  • QRS axis
  • ST segment
52
Q

What is every small box on an ECG worth (s)?

A

0.04 seconds

53
Q

What is every large box on an ECG worth (s)?

A

0.2 seconds

54
Q

What is every small box on an ECG worth (mV)?

55
Q

What is every large box on an ECG worth (mV)?

56
Q

How do you calculate HR on an ECG?

A

count the number of big squares in the R-R interval

300/number of boxes

57
Q

Where is the negative electrode for the unipolar leads?

A

1/3 (RA+LA+LL) - middle of the body

58
Q

What are the lateral leads?

A

I, aVL, V5, V6

59
Q

What are the inferior leads?

A

II, III, aVF

60
Q

What are the septal leads?

61
Q

What are the anterior leads?

62
Q

What coronary artery is associated with the lateral leads?

A

Left circumflex

63
Q

What coronary artery is associated with the inferior leads?

A

Right coronary

64
Q

What coronary artery is associated with the septal leads?

A

Left anterior descending

65
Q

What coronary artery is associated with the anterior leads?

A

Left anterior descending

66
Q

What is the normal length of an R-R interval?

A

0.6-1.2 seconds

67
Q

What is the normal length of a P wave?

68
Q

What is the normal length of a P-R interval?

69
Q

What is the normal length of a QRS complex?

70
Q

What is the normal length of a Q-T interval?

71
Q

What is the normal length of a T wave?

72
Q

How do you calculate cardiac axis?

A
  • calculate the net deflection of the QRS complex of II and aVL (parallel leads)
  • SoH CaH ToA to find the angle
  • 60 - angle found =
73
Q

Where are the electrodes for aVF?

A 
\+ = 1/2 (RA+LA)
- = LL
74
Q

Where are the electrodes for aVL?

A 
\+ = LA
- = 1/2 (RA+LL)
75
Q

Where are the electrodes for aVR?

A 
\+ = RA
- = 1/2 (LA+LF)
76
Q

What is the PR interval?

A

start of P wave to the start of the QRS complex

77
Q

When is a change in the PR interval problematic?

A

> 0.2 seconds (one big box)

78
Q

What can cause a change in the PR interval?

A

atrial ectopic focus (irritable atrial cell)
- father from AV, the longer the PR interval
first degree heart block

79
Q

What is a prolonged QRS complex?

A

> 0.12seconds

80
Q

What can cause changes in the QRS complex?

A
  • ventricular ectopic focus
  • irritated ventricular cell
  • longer to depolarise > longer QRS
81
Q

What condition is characterised by tachycardia and a long QT interval?

A

Torsades de Pointes

82
Q

What is the relationship between the QT interval and heart rate?

A

as heart rate increases, QT interval shortens

83
Q

What can causes changes (prolonged) QT interval?

A
  • medications: amiodarone (impacts ion channels)

- congenital (LGTI 1, 2, 3)

84
Q

What is Left Ventricular Hypertrophy?

A

abnormal musculature in the left ventricle

no new vasculature

85
Q

How does Left Ventricular Hypertrophy present on an ECG?

A

an enlarged QRS complex - seen on lateral leads

86
Q

What can cause Left Ventricular Hypertrophy?

A
  • pressure overload
    increased BP > increased afterload > increased pressure > changes in modelling and increased stiffness (no relaxation)
  • volume overload
    changes in systolic function > heart works harder to maintain output
  • angiotension II
    sympathetic activation of the renin-aldosterone-angiotensin system
87
Q

What indicates an NSTEMI/Unstable angina?

A
  • ST depression
  • T wave inversion
    Lead II and III

BRS YR2 (70 decks)

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