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Cardiovascular system > Introduction to the ECG > Flashcards

Introduction to the ECG Flashcards

1
Q

what is an SLL I ECG?

A

standard limb lead I, recordings made from left arm with respect to right arm

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2
Q

what is an SLL II ECG?

A

recordings made from left leg with respect to right arm

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3
Q

what is an SLL III ECG?

A

recordings made from left leg with respect to left arm

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4
Q

a wave of depolarisation moving from left leg to right arm will show what sort of blip on a SLL II ECG?

A

a negative blip

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5
Q

a wave of depolarisation from the right arm to the left leg will show what on a SLL II ECG?

A

a positive blip, like in atrial depolarisation and ventricular depolarisation

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6
Q

a wave of repolarisation moving from the left leg to the right arm will show what on a SLL II ECG?

A

a positive blip, like in ventricular repolarisation

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7
Q

what is the PR interval?

A

time from atrial depolarisation and ventricular depolarisation, the time is mainly due to the transmission through the AV node

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8
Q

what is the QT interval?

A

time spent while ventricles are depolarised

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9
Q

why can’t atrial repolarisation be seen on the ECG?

A

Because atrial repolarisation coincides with ventricular depolaristion. Ventricular depolarisation involves much more tissue depolarising much faster so it swamps any signal from atrial repolarisation.

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10
Q

why does the QRS complex contain three blips?

A

1st blip – the interventricular septum depolarises from left to right, direction is towards right arm so is negative
2nd blip – the bulk of the ventricle depolarises from the endocardial to the epicardial surface, this produces a vector towards the left leg
3rd – the upper part of the interventricular septum depolarises towards the right arm so is negative

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11
Q

why is the T wave positive

A

Because the action potential is longer in endocardial cells than in epicardial cells, so the wave of repolarisation runs in the opposite direction to the wave of depolarisation. ie a wave of repolarisation moving away from the recording electrode produces another positive-going blip.

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12
Q

Why is the R-wave bigger in SLL II than in SLL I or SLL III?

A

Because the main vector of depolarisation is in line with the axis of recording from the left leg with respect to the right arm.

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13
Q

What happens to the magnitude of the R wave whe the heart is rotated left or develops hypertrophy on the left or atrophy on the right?

A

this causes axis deviation. which means that, blip in SLL I will be larger and the blips in SLL II and III willl be smaller

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14
Q

what are the augmented limb leads?

A

aVR, aVL, aVF

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15
Q

what is aVR?

A

a recording made from the right arm with respect to half way between the left leg and arm (SLL III)

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16
Q

what is aVL?

A

a recording made from the left arm with respect to half way between the left leg and right arm (SLL II)

17
Q

what is aVF?

A

a recording made from the left leg to half way between the left and right arm (SLL I)

18
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

19
Q

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

A

These are arranged in front of the heart and therefore look at the same events, but in the horizontal (or transverse) plane

20
Q

how do the blips on the ECG change moving from precodial lead V1 to V6?

A

it is negative at V1 and increases up until it is greatest at V5, V6 is slightly smaller than V5

21
Q

what is the rhythm strip on an ECG?

A

a continuous line of SLL II trace

22
Q

how fast does an ECG run?

23
Q

how long is the calibrating pulse and how much space does it take up?

A

0.2 sec and 1 large square

24
Q

how do you determine the HR from the rhythm strip?

A

either:
measure the R-R interval and work out how many in 60 sec
or
count 30 large squares (=6sec) then multiply by 10

25
Q

what us bradycardia?

26
Q

what is tachycardia?

27
Q

what does the U wave correspond to and where does it lie?

A

the repolarisation of the papillary muscle, it lies after the T wave

28
Q

what is STEMI?

A

ST elevated myocardial infarction, the ST region on the ECG is raised

29
Q

what is an NSTEMI?

A

a non-ST elevated myocadial infarction

30
Q

which MI is more serious, STEMI or NSTEMI?

31
Q

what is the normal range for the PR interval?

A

0.12-0.2 sec

32
Q

what is the normal time for QRS?

33
Q

what is the normal time for QT interval?

A

varies heart rate, but normally 0.42 at 60 bpm

Cardiovascular system (40 decks)

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