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BRS YR2 > Electrocardiography and Rhythm Disorders > Flashcards

Electrocardiography and Rhythm Disorders Flashcards

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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
Where is V5 placed ?
- Left anterior axillary line | - 5th intercostal space
26
What are the 3 augmented vector lead?
- Left mid axillary line | - 5th intercostal space
27
Can you shock during asystole?
No
28
What are the characteristics of sinus rhythm?
- every P wave is followed by a QRS complex - regular rate (even R-R intervals) - normal HR (60-100bpm)
29
What causes a sinus arrhythmia?
- stress - exercise - stimualtants
30
What are the characteristics of atrial fibrillation?
- oscillating baseline due to asynchronous atrial contraction - irregular rhythm, slow rate
31
What are the characteristics of atrial flutter?
- regular, saw tooth pattern in baseline | - atrial:ventricular contraction at 3:1,2:1 ratio or higher
32
What are the characteristics of a first degree heart block?
- prolonged PR segment/interval caused by slower AV conduction - regular rhythm (1:1, P waves:QRS complexes)
33
What are the characteristics of second degree heart block (Mobitz I / Wenckebach)?
- 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
34
What are the characteristics of second degree heart block (Mobitz II)?
- 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
35
What are the characteristics of third degree (complete) heart block?
- 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
when does something have a non-sinus rhythm?
when the electrical stimulation of the heart isn't initiated by the SA node
37
What are the characteristics of ventricular tachycardia?
- P waves hidden - dissociated atrial rhythm - rate is regular and fast (100-200bpm) - shockable rhythm
38
What are the characteristics of ventricular fibrillation?
- HR is irregular and >250bpm - heart is unable to generate output - shockable rhythm
39
What are the characteristics of an ST elevation?
- visible P waves followed by a QRS complex (1:1) - regular rate and rhythm - ST segment is elevated >2mm above the isoelectric line
40
What are the characteristics of an ST depression?
- visible P waves followed by a QRS complex (1:1) - regular rhythm and normal rate - depressed >2mm below the isoelectric line
41
What causes ST depression?
myocardial ischaemia - coronary insufficiency
42
What can cause ST elevation?
infarction (tissue death due to hypoperfusion) - STEMI
43
What risk increases when ventricular tachycardia occurs?
high risk of deteriorating into fibrillation (cardiac arrest)
44
What causes Mobitz-1 type second degree heart block?
a diseased AV node
45
What is first degree heart block indicative of?
benign, progressive disease of aging
46
Where does atrial flutter tend to be seen?
leads II, III, and aVF
47
What can be a complication associated with atrial fibrillation?
turbulent blood flow pattern increases the risk of clots
48
What is the impact of atrial fibrillation on cardiac output?
minimal, as atria are not essential to the cardiac cycle
49
What tends to cause sinus tachycardia?
often a physiological response, secondary to another factor
50
What can cause sinus bradycardia?
- can be normal/healthy - medication - vagal stimulation
51
What are the steps of reading an ECG?
- rate and rhythm - P wave and PR interval - QRS duration - QRS axis - ST segment
52
What is every small box on an ECG worth (s)?
0.04 seconds
53
What is every large box on an ECG worth (s)?
0.2 seconds
54
What is every small box on an ECG worth (mV)?
0.1mV
55
What is every large box on an ECG worth (mV)?
0.5mV
56
How do you calculate HR on an ECG?
count the number of big squares in the R-R interval | 300/number of boxes
57
Where is the negative electrode for the unipolar leads?
1/3 (RA+LA+LL) - middle of the body
58
What are the lateral leads?
I, aVL, V5, V6
59
What are the inferior leads?
II, III, aVF
60
What are the septal leads?
V1, V2
61
What are the anterior leads?
V3, V4
62
What coronary artery is associated with the lateral leads?
Left circumflex
63
What coronary artery is associated with the inferior leads?
Right coronary
64
What coronary artery is associated with the septal leads?
Left anterior descending
65
What coronary artery is associated with the anterior leads?
Left anterior descending
66
What is the normal length of an R-R interval?
0.6-1.2 seconds
67
What is the normal length of a P wave?
80ms
68
What is the normal length of a P-R interval?
120-200ms
69
What is the normal length of a QRS complex?
<120ms
70
What is the normal length of a Q-T interval?
420ms
71
What is the normal length of a T wave?
160ms
72
How do you calculate cardiac axis?
- 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
Where are the electrodes for aVF?
``` + = 1/2 (RA+LA) - = LL ```
74
Where are the electrodes for aVL?
``` + = LA - = 1/2 (RA+LL) ```
75
Where are the electrodes for aVR?
``` + = RA - = 1/2 (LA+LF) ```
76
What is the PR interval?
start of P wave to the start of the QRS complex
77
When is a change in the PR interval problematic?
>0.2 seconds (one big box)
78
What can cause a change in the PR interval?
atrial ectopic focus (irritable atrial cell) - father from AV, the longer the PR interval first degree heart block
79
What is a prolonged QRS complex?
>0.12seconds
80
What can cause changes in the QRS complex?
- ventricular ectopic focus - irritated ventricular cell - longer to depolarise > longer QRS
81
What condition is characterised by tachycardia and a long QT interval?
Torsades de Pointes
82
What is the relationship between the QT interval and heart rate?
as heart rate increases, QT interval shortens
83
What can causes changes (prolonged) QT interval?
- medications: amiodarone (impacts ion channels) | - congenital (LGTI 1, 2, 3)
84
What is Left Ventricular Hypertrophy?
abnormal musculature in the left ventricle | no new vasculature
85
How does Left Ventricular Hypertrophy present on an ECG?
an enlarged QRS complex - seen on lateral leads
86
What can cause Left Ventricular Hypertrophy?
- 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
What indicates an NSTEMI/Unstable angina?
- ST depression - T wave inversion Lead II and III

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