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BMD221 Biomedical Physiology > Week 2 ECG > Flashcards

Week 2 ECG Flashcards

1
Q

How are electrical signals of the heart detected

A
  1. Electrodes are placed on skin
  2. Machine records heart rhythm
  3. By recording waves of electrical activity
  4. Produces an ECG
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2
Q

What does an ECG measure

A

Effect on anatomical features of the heart
Not cell membrane potential
Shows PQRS wave

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3
Q

What does the PQRS wave show

A

Movement of an electrical wave across skin

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4
Q

P of PQRS

A

Atrial depol / contraction

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5
Q

QRS of PQRST

A

Bundle of His, purkinje fibres
Ventricular depol
Contraction

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6
Q

T of PQRST

A

Ventricular relaxation / repolarisation

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7
Q

SAN relation to ECG

A
  1. Not seen much as there are not a lot of cells
  2. Also Not directional
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8
Q

Atrial muscle relation to ECG

A

Takes up most of the P wave
- lots of muscle tissue
- depol = upward

  1. Steep opening of sodium channels ⬆️
  2. L type calcium ion channels open = plateau
  3. Calcium channels close, K+ continues to flow out
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9
Q

AVN relation to ECG

A

Small mass - seen at the end of the P wave

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10
Q

Common bundle, branches and purkinje fibres + ECG

A

Not seen due to small area

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11
Q

Ventricular muscle relation to ECG

A
  • largest muscle mass
  • shows as PQRST complex
  • depolarisation + repolarisation
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12
Q

What is happening at the level stage between S and T

A

L type calcium channels remain open for a long time

So there is no change = levelling on the ECG

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13
Q

What is happening during the T wave

A

Repolarisation but in the opposite direction

So is seen as upwards - the same as depol

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14
Q

What anatomical feature of the heart has the largest impact on the ECG

A

Ventricular muscle

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15
Q

What direction is an ECG

A

Too left to bottom right

^ affects how depol and repol are seen

  • depol is normally up, repol is down
    Reversed when going from bottom right to top left
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16
Q

What are segments on an ECG

A

Area between waves
1. PR
2. ST

17
Q

What are the two intervals on an EVG

A

PR and QT

Named from the first wave

18
Q

What is an atrioventricular block

A

Abnormal or absent conduction
So downstream tissue will not be excited by the travelling AP wave

19
Q

How is an AV block managed

A

Pacemaking tissue further along will generate its own APs

20
Q

Conduction in 1st degree AV blocks

A

Conduction through AVN is slowed but not interrupted

21
Q

P-QRS in 1st degree AV block

A

One P for every QRS (as normal)
But there is a longer gap
Of more than 200ms

22
Q

Conduction in 2nd degree AV block

A

Partially interrupted
But mostly proceeds

23
Q

P-QRS complexes in 2nd degree AV blocks

A

Several QRS complexes have no P wave

24
Q

Conduction in 3rd degree AV blocks

A

Conduction through the AVN is blocked

25
P-QRS complexes in 3rd degree AV blocks
No correspondence QRS complexes are very infrequent Less than 40bpm
26
Why is the PQRS complex irregular in 3rd degree AV block
Myogenic cells beyond the AVN produce their own APs But at a much slower rate So is not coordinated with the SAN
27
What is Arrhythmia
Normal beating but SAN sends irregular signals
28
What does arrhythmia look like on an ECG
Normal PQRS complex but is irregular
29
Tachycardia
A very fast rhythm Can apply to atria/ventricles/both Very high rate = flutter
30
What does tachycardia look like on an ECG
Complexes are normal and evenly spaced But rate > 100bpm
31
Bradycardia
Slow heart beat Atria/ventricles/both
32
What does bradycardia look like on an ECG
Complexes normal and evenly spaced but rate < 60 bpm
33
What is fibrillation
One or both chambers locked in constant uncoordinated beating
34
What does atrial fibrillation look like on an ECG
Baseline and ventricular response both irregular
35
What does ventricular fibrillation look like on an ECG
Rapid wide irregular ventricular complexes
36
What causes fibrillation
Re-entry - conducted wave circles back on itself
37
What is wolf Parkinson white syndrome
A common re-entry - occurs when the bundle of Kent (conductive tissue) crosses atrium to the ventricle - so signal passes along the ventricle - some parts contract before others - so there is no synchrony

BMD221 Biomedical Physiology (6 decks)

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