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Cardiovasc > ECG > Flashcards

ECG Flashcards

1
Q

In which direction does the ventricles depolarise in term of layers ?

A

Endocardium to Epicardium

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2
Q

What is normal sinus rhythm ?

A
  • Depolarisation initiated by SA node
  • 60-100 heart rate
  • Regular
  • P wave before each QRS
  • QRS< 3 small boxes (0,12s)
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3
Q

Why is the bundle of His the only path from atria to ventricles for the current ?

A

Because of the fibrous ring (containing the 4 valves) which prevents direct contact between atrial and ventricular myocytes

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4
Q

Describe the wave of depolarisation toward the electrode

A

Positive complex (up then down)

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5
Q

Describe depolarisation going away from electrode

A

Negative complex

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6
Q

Describe Repolarisation towards electrode

A

Negative complex

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7
Q

Where is the SA node ?

A
  • top right corner of right atrium

- near junction of SVC and right atrium

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8
Q

Can we see SA node depolarisation on an ECG ?

A

NO

Insufficient signal to register

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9
Q

What causes the P wave ?

A

Atrial depolarisation : spread through atrial muscles fibres and internodal pathways

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10
Q

In which direction does the atrial depolarisation occur ?

A

Downwards and to the left

Towards AV node

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11
Q

What happens at the AV node and why ?

A

Delay of current to allow time for atrial contraction

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12
Q

What contribute to the isoelectric segment 1b of an ECG ?

A
  • Delay of current at AV node

- Current traveling through Bundle of His and Purkinje system

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13
Q

With part of the myocardium depolarises first ? And in which direction ?

A
  • Interventricular septum

- from Left to right

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14
Q

What does the Septum depolarisation look like on an ECG and why ?

A
  • Q wave :small downward deflection

- Depolarisation from left to right , away from electrode so down , but oblique so small

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15
Q

What does the R wave represent ?

A

Depolarisation of Apex and Free ventricular wall

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16
Q

Describe the R wave , why does it look like that ?

A
  • Large upward deflection
  • upward because towards electrode
  • large because large muscle mass
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17
Q

What does the S wave represent ?

A

End of depolarisation .

Of base of ventricles

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18
Q

Why does Repolarisation cause an upward T wave ?

A

Repolarisation occurs in opposite direction of depolarisation , so away from electrode (double negative)

19
Q

What does QRS represent ?

A

Ventricular depolarisation

20
Q

How many electrodes are needed for the recording of an ECG ?

A

10
4 limbs
6 chest

21
Q

In which plane are the limb leads (views)?

A

Vertical

22
Q

In which plane are the chest leads ?

A

Horizontal

23
Q

How many views are given by the limb electrodes ? Which one?

A

6
aVF, aVR, aVL
I, II, III

24
Q

Which limb lead are looking at the inferior surface of the hear ?

A

II, III, aVF

25
Q

Lead I ,II and III are obtained thanks to which limb electrodes ?

A

I: right arm (-) to left arm (+)
II : right arm(-) to left leg (+)
III: left arm(-) to left leg (+)

26
Q

Which lead are the best to look at inferior myocardial infarction ?

A

II, III, aVF

27
Q

Lead I and aVL are looking at which side of the heart ?

A

Left

28
Q

Where are electrodes 1 and 2 located ?

A

4th intercostal space , on each side of the sternum

29
Q

Leads V1 and V2 face which part of the heart ?

A

Right ventricle and septum

30
Q

Where is the 4th chest lead ?

A

5th intercostal space , mid clavicle

31
Q

Where is the 6th chest electrode ?

A

5th intercostal space , below axilla

32
Q

Chest leads V3 and V4 face which part of the heart ?

A

Apex and wall of ventricles

33
Q

Which chest lead face the left ventricle ?

A

V5 and V6

34
Q

True or False : V1 and V6 have opposite traces ?

A

True , Q upwards for V1 and downwards for V6 because depolarisation from left to right (septum)

35
Q

How many seconds is a small square ?

A

0,04 s= 40ms

36
Q

2 large boxes up is womanly mV ?

A

1

37
Q

1 second is …large squares

A

5

38
Q

How do you calculate the heart rate (regular) ?

A

(300 squares = 1 minute)

300 / nbr of large boxes between 2 cardiac cycle (R-R)

39
Q

How do you calculate the heart rate for an irregular rhythm ?

A

Count nbr of QRS complex in 6 seconds (6x5 large boxes ) then multiply by 10

40
Q

What does PR represent? Where to measure ?

A
  • Time between atrial and ventricular depolarisation

- Start of P wave -Start of Q wave

41
Q

What does a longer PR interval indicates ?

A

Slow conduction from atria to ventricle = First degree heart block

42
Q

What is the ST segment and where do you measure ?

A
  • Isoelectric segment between end of depolarisation and Repolarisation
  • End of S to start of T wave
43
Q

What does raised or depressed ST segment indicates?

A

MI or Ischaemia

44
Q

What does a prolonged QT segment indicates ?

A

Prolonged Repolarisation > can lead to arrhythmias

Cardiovasc (3 decks)

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