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S2 Cardiovascular System > 3/ a first look at the ECG > Flashcards

3/ a first look at the ECG Flashcards

1
Q

which pair of electrodes can recordings be made from?

A

any pair

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2
Q

which pair is referred to as SLL I?

A

left arm and right arm

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3
Q

which pair is referred to as SLL II?

A

left leg and right arm

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4
Q

which pair is referred to as SLL III?

A

left leg and left arm

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5
Q

what does a wave of approaching depolarisation cause on the recording?

A

an upward-going blip

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6
Q

which events are transmitted better between fast and slow ones?

A

fast

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7
Q

where is the typical ECG recorded from? which electrode is the reference?

A

standard limb lead II (SLL II), the recording is LL’s position relative to the RA

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8
Q

which direction does the main wave of depolarisation take?

A

down the ventricles, through the body fluids, towards the electrode on the left leg

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9
Q

a wave of depolarisation approaching the left leg will cause a positive/negative relative to the right arm?

A

positive

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10
Q

a wave of depolarisation going away from the left leg will cause a positive/negative relative to the right arm?

A

negative

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11
Q

a wave of repolarisation approaching the left leg will cause a positive/negative relative to the right arm?

A

negative

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12
Q

a wave of repolarisation going away from the left leg will cause a positive/negative relative to the right arm?

A

positive

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13
Q

what is the P wave caused by? (from SLL II)

A

atrial depolarisation

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14
Q

what is the QRS complex caused by? (from SLL II)

A

ventricular depolarisation

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15
Q

what is the T wave caused by? (from SLL II)

A

ventricular depolarisation

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16
Q

what does the PR interval correspond to? what does the impulse go through during this time? how long is the PR interval?

A

time from atrial depolarisation to ventricular depolarisation, mainly due to transmission through the AV node (0,12-0,2sec)

17
Q

what does the QRS time correspond to? how long is it usually?

A

time for the whole of the ventricle to depolarise (normally about 0,08sec)

18
Q

what does the QT interval correspond to? how long is the QT interval?

A

time spend while ventricles are depolarised (varies with HR but normally about 0,42sec at 60bpm)

19
Q

is atrial repolarisation visible on the ECG?

A

no because atrial repolarisation coincides with ventricular depolarisation- ventricular depolarisation involves much more tissue depolarising much faster so it swamps any signal from atrial repolarisation

20
Q

what does the Q part of the QRS complex correspond to?

A

the inter ventricular septum depolarises from left to right

21
Q

what does the R part of the QRS complex correspond to?

A

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

22
Q

what does the S part of the QRS complex correspond to?

A

the upper part of the inter ventricular septum depolarises

23
Q

why is the T-wave positive + going?

A

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

24
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

25
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

26
Q

what extra information do the augmented limb 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 (i.e. recordings from SLLs I, II, III and aVR, aVL, aVF give you 6 different views of events occurring in the frontal (or vertical) plane

27
Q

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

A

these are arranged in front on the heart and therefore look at the same events, bt in the horizontal (or transverse) plane- (slide 15)

28
Q

what plane are the limb leads in? how many angles?

A

frontal plane, 6 angles

29
Q

what plane are the precordial leads in? how many angles?

A

transverse plane, 6 angles

30
Q

what information is brought by the rhythm strip?

A

HR (60-100bpm normal)

31
Q

what else can the rhythm strip tell you?

A
  • is each QRS complex preceded by a P-wave
  • is the PR interval too short (<0,12sec) or too long (>0,2sec)
  • is the QRS complex too wide (>0,12sec)
  • is the QT interval too long (>0,42sec at 60bpm)
32
Q

what is a STEMI?

A

ST elevated myocardial infarction

33
Q

what is a NSTEMI?

A

non-ST elevated myocardial infarction

34
Q

what does an elevation of ST mean?

A

something has gone seriously wrong (cardiologists use it to classify severity of heart attack)

35
Q

which is worst between STEMI and NSTEMI?

A

STEMI

36
Q

learning outcomes

A

slide 22

S2 Cardiovascular System (11 decks)

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