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Cardiovascular System > A First Look at the ECG > Flashcards

A First Look at the ECG Flashcards

1
Q

What plane do SLLs look at events in the heart?

A

vertical/frontal

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2
Q

How does SLL I record activity?

A

Records from LL wrt RA

i.e. + electrode is at the LA

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3
Q

How does SLL II record activity?

A

Records from the LL wrt to the RA

i.e. + electrode is at the LL

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4
Q

How does SLL III record activity?

A

Records from the LL wrt the LA

i.e. + electrode is at the LL

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5
Q

What are the three basic principles behind ECG readings?

A
  • Fast events are transmitted well
  • Slow events are not
  • A wave of approaching depolarisation causes an upward blip.
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6
Q

How would depolarisation and repolarisation of the action potential be transmitted on the ECG?

A

Very well (i.e. larger wave)

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7
Q

How would the plateu of the action potential be transmitted on the ECG?

A

Not very well

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8
Q

What exactly is it that the ECG is recording between the electrodes?

A

The difference in potential between the recording electrode and another with respect to it.

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9
Q

Why SLL records the main wave of depolarisation?

A

SLL II

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10
Q

As the wave of _____________ passes the electrode on the left leg it creates a _________ potential relative to the right arm.

A

depolarisation

positive

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11
Q

SLL II:

A wave of repolarisation approaching the left leg will cause a ________ potential relative to the right arm.

A

negative

downward blip

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12
Q

SLL II:

A wave of depolarisation approaching the left leg will cause a __________ potential relative to the right arm.

A

positive

upward blip

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13
Q

SLL II:

It follows that a wave of repolarisation going away from the left leg will cause a _________ potential relative to the right arm.

A

positive

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14
Q

SLL II:

It follows that a wave of depolarisation going away from the left leg will cause a _________ potential relative to the right arm.

A

negative

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15
Q

Which direction would be considered the direction of forward travel?

  • negative to positive
  • positive to negative
A

negative to positive

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16
Q

P wave is caused be ____ _____.

A

atrial depolarisation

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17
Q

____ complex is caused by ____ ____.

A

QRS

ventricular depolarisation

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18
Q

T wave is caused by ____ _____.

A

ventricular repolarisation

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19
Q

What does the PR interval correspond to?

A

time from atrial depolarisation to ventricular depolarisation

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20
Q

What is the normal value for the PR interval?

A

0.12 - 0.2 sec

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21
Q

What does the duration of the QRS complex correspond to?

A

time taken for the whole of the ventricle to depolarise.

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22
Q

What is the normal time range for the QRS complex?

A

0.08 sec

23
Q

What does the QT interval correspond to?

A

time spent while ventricles are depolarised.

24
Q

What is the normal time range for the QT interval?

A

normally around 0.42 sec at 60bpm

25
Q

Why is the PR interval longer than the QRS complex?

A

There is slow transmission through the AV node between the atria and ventricles.

26
Q

Why can we not see atrial repolarisation on an ECG recording?

A
  • Atrial repolarisation coincides with ventricular depolarisation.
  • Ventricular depolarisation involves much more tissue depolarising much faster so it swamps any signal from atrial repolarisation.
  • It is there, but it is lost.
27
Q

Why is the QRS complex so complex?

A

Because different parts of the ventricle depolarise at different times in different directions.

28
Q

The interventricular septum depolarises from _____ to _____.

This produces an _______ facing blip.

A

left, right

downward

29
Q

The bulk of the ventricle depolarises from the endocardial to the epicardial surface.

The _________ arrow travels towards the _______, which is the ________ electrode.

This produces a _____ wave facing in the ________ direction.

A

resultant
LL
positive

large
upward

30
Q

The upper part of the interventricular septum depolarises in the direction ________ the positive electrode.

This produces a _________ facing curve.

A

opposite

downward

31
Q

Why is the R phase larger than the Q and S phase?

A

The R phase spreads in the direct path of SLL II therefore produces the strongest reading on the ECG.

The main vector of depolarisation is in line with the axis of recording.

32
Q

Why is the T-wave positive-going if it is a repolarisation phase?

A

Seen as the wave for repolarisation is running in the opposite direction to the wave of depolarisation, that is that it is travelling towards the RA from the LL.

Negative phase in negative direction = positive wave

33
Q

What would happen if the heart was rotated to the left, or developed hypertrophy on the left, or atrophy on the right?

A

Causes axis deviation, readings would be skewed.

34
Q

What extra information do the augmented limb leads give you?

A

By recording from one limb lead with respect to the other two combined, it gives you 3 other perspective on events in the heart.

35
Q

How many different views of events can be measured from the vertical plane?

What leads are used?

A

6

SLL I-III
aVL, aVR, aVF

36
Q

How does aVR record readings on an ECG?

A

From the RA wrt to the LA and LL.

37
Q

How does aVF record readings on an ECG?

A

From the LL wrt to the RA and LA.

38
Q

How does aVL record readings on an ECG?

A

From the LA wrt to the RA and LL.

39
Q

What extra information do the precordial (chest) leads give you?

A

They look at events in the heart in the transverse plane.

40
Q

There are 6 precordial leads attached to the chest (V1-V6).

Which one will produce the most negative going wave, and why?

A

V1

It records depolarisation from an angle most distant from the resultant vector.

41
Q

What is the phenomena known as where the recording changes from V1 - V6 with precordial leads?

A

Progression

42
Q

The limb leads look at the spread of depolarisation (and repolarisation) from ___ angles in the _______ plane.

A

6

frontal

43
Q

the precordial leads look at the spread of depolarisation (and repolarisation) from ____ angles in the _________ plane.

A

6

transverse

44
Q

What can you calculate from the rhythm strip?

A

HR

Whether a patient is sinus bradycardia, sinus tachycardia

45
Q

On the rhythm strip, paper should run at ________.

A

25mm/sec

46
Q

Calibrating pulse is ____ sec = 1 large square (5mm)

A

0.2

47
Q

How do you determine HR from a rhythm strip?

A

Count the R waves in 30 large squares (30 x 0.2 = 6 sec) and multiply by 10 (to give for 60s).

48
Q

What is normal range for HR?

A

60-100bpm

49
Q

When is a patient bradycardic?

A

Below 60bpm

50
Q

When is a patient tachycardic?

A

Above 100bpm

51
Q

On the rhythm strip, what could an abnormal PT interval suggest?

(i.e. <0.12s or >0.2s)

A

Stage 1 heart block

52
Q

What does STEMI and NSTEMI mean?

A

ST elevated myocardial infarction

non-ST elevated myocardial infarction

53
Q

Which is more serious, STEMI or NSTEMI?

A

STEMI

Cardiovascular System (37 decks)

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