ECG Revisted Flashcards

1
Q

What can ECGs helps see?

A
  • Conduction abnormalities
  • Structural abnormalities
  • Perfusion abnormalities
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2
Q

Why are ECGs helpful?

A
  1. Relatively cheap and easy to undertake
  2. Reproducible between people and centres
  3. Quick turn around on results/report
  4. Leads are views of the heart
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3
Q

What is a vector?

A

A quantity that has both magnitude and direction

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4
Q

How is a vector usually shown?

A

by an arrow in the net direction of movement, whose size reflects the magnitude

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5
Q

What does an isoelectric line represent?

A

no net change in voltage I.e. vectors are perpendicular to the lead

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6
Q

What does the width of of the deflection show?

A

‘duration’ of the event

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7
Q

Which direction are upward deflection?

A

towards the cathode (+)

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8
Q

Which direction are downward deflection?

A

towards the anode (-)

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9
Q

What is each wave composed of?

A

both the up and downstrokes

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10
Q

What is the P wave?

A

electrical signal that signifies relaxation of the ventricles

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11
Q

What is the QRS complex?

A

electrical signal that stimulates contraction of the ventricles (ventricular systole)

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12
Q

What is the T wave?

A

electrical signal that stimulates contraction of the atria

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13
Q

What happens at the SAN? What does it look like on a ECG?

A
  1. Auto-rhythmic myocytes (sponateanously depolarising)
  2. Atrial depolarisation
  3. Wide as slow and not high as small and going more towards positive then negative vector
    (P)
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14
Q

What happens at the AVN?

A
  1. AVN depolarisation
    2, Isoelectric ECG
  2. Slow signal transduction
  3. Protective
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15
Q

What happens at the bundle of his?

A
  • Rapid conduction

- Insulated

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16
Q

What happens at the bundle branches?

A

Septal depolarisation (S)

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17
Q

What happens at the purkinje fibres (1)?

A

Ventricular depolarisation (R)

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18
Q

What happens at the purkinje fibres (2)?

A

Late ventricular depolarisation (S)

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19
Q

What does the fully depolarised ventricles look like on ECG?

A

Isoelectric line

20
Q

What is ventricular repolarisation?

A

T wave

21
Q

Where is lead I placed?

A
  • Right Arm to Left Arm

- One L

22
Q

Where is lead II placed?

A
  • Right Arm to Left Leg

- Two L’s

23
Q

Where is lead III placed?

A
  • Left Arm to Left Leg

- Three L’s

24
Q

How do you read electrode placement?

A
  1. English is read left to right and top to bottom, polarity does that too
  2. Drawn as a triangle and reading left to right and top to bottom, the first electrode of each pair you reach is the anode (-ve)
25
Q

Where is V1 placed?

A
  • Right sternal border

- In the 4th intercostal space

26
Q

Where is V2 placed?

A
  • Left sternal border

- In the 4th intercostal space

27
Q

Where is V3 placed?

A

-Halfway between V2 and V4

28
Q

Where is V4 placed?

A
  • Mid-clavicular line

- 5th intercostal space

29
Q

Where is V5 placed?

A
  • Anterior axillary line

- At level of V4

30
Q

Where is V6 placed?

A
  • Mid-axillary line

- At level of V4

31
Q

What is the bottom of the ECG reading?

A

Rhythm strip

32
Q

What does sinus rhythm look like?

A
  1. Each P wave is followed by a QRS complex (1:1)
  2. Rate is regular (even R-R intervals) and normal (83bpm)
  3. Otherwise unremarkable
33
Q

What does sinus bradycardia look like?

A
  1. Each P wave is followed by a QRS complex (1:1)
  2. Rate is regular (even R-R intervals) and slow (56bpm)
  3. Can be healthy, caused by medication or vagal stimulation
34
Q

What does sinus tachycardia look like?

A
  1. Each P wave is followed by a QRS wave (1:1)
  2. Rate is regular (even. R-R intervals) and fast (107bpm)
  3. Often a physiological response (I.e. secondary)
35
Q

What does sinus arrhythmia look like?

A
  1. Each P wave is followed by a QRS wave
  2. Rate is irregular (variable R-R intervals) and normal-ish (65-100mph)
  3. R-R interval varies with breathing cycle
36
Q

What does atrial fibrillation look like?

A
  1. Oscillating baseline - atria contracting asynchronously
  2. Rhythm can be irregular and rate may be slow
  3. Turbulent flow pattern increases clot risk
  4. Atria not essential for cardiac cycle
37
Q

What does atrial flutter look like?

A
  1. Regular saw tooth pattern in baseline (II,III, avF)
  2. Atrial to ventricular beats a 2:1 ratio, 3:1 ratio or higher
  3. Saw-tooth not always visible in all leads
38
Q

What does first-degree heart block look like?

A
  1. Prolonged PR segment/interval caused by slower AV conduction
  2. Regular rhythm 1:1 ratio of P-waves to QRS complexes
  3. Most benign heart block, but a progressive disease of ageing
39
Q

What does secondary degree heart block (Mobitz I) look like?

A
  1. Gradual prolongation of the PR interval until beat skipped
  2. Most P-waves followed by QRS; but some P waves are not
  3. Regular irregular: caused by a diseased AV node
  4. Also called Wenckebach
40
Q

What does secondary degree heart block (Mobitz II) look like?

A
  1. P waves are regular but only some are followed by QRS
  2. No P-R prolongation
  3. Regular irregular: success to failures (e.g. 2:1) or random
  4. Can rapidly deteriorate into third degree heart block
41
Q

What does third degree (complete) heart block look like?

A
  1. P waves are regular, QRS are regular, but no relationship
  2. P waves can be hidden within bigger vectors
  3. A truly non-sinus rhythm - back-up pacemaker in action
42
Q

What does ventricular tachycardia look like?

A
  1. P waves hidden: dissociated atrial rhythm
  2. Rate is regular and fast (100-200bpm)
  3. At high risk of deteriorating into fibrillation (Cardiac arrest)
  4. Shockable rhythm - defibrillators widely available
43
Q

What does ventricular fibrillation look like?

A
  1. Heart rate irregular and 250 bpm and above
  2. Heart unable to generate an output
  3. Shockable rhythm - defibrillators widely available
44
Q

What does ST elevation look like?

A
  1. P waves visible and always followed by QRS
  2. Rhythm is regular and rate is normal (85bpm)
  3. ST-segment is elected >2mm above the isoelectric line
  4. Caused by infarction (tissue death caused by hypo perfusion)
45
Q

What does ST depression look like?

A
  1. P Waves visible and always followed by QRS
  2. Rhythm is regular and rate is normal (95bpm)
  3. ST-segment is depressed >2mm below the isoelectric line
  4. Caused by myocardial ischaemia (coronary insufficiency)