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Flashcards in Understanding ECGs Deck (43):
1

what type of activity does an ECG show?

electrical activity
(not mechanical ie wont see valves closing etc)

2

what is the name of the recording of potential differences in the heart?

electrocardiogram

3

what is the name for the separation of charge one after the other?
(depolarisation and then hyperpolarisation)

dipole

4

what do electrodes record?

the difference in potential between two points

5

when will the net potential measured by the electrodes be 0mV?

when the lead (ie imaginary line between 2 electrodes) is perpendicular to the dipole

6

what is the leading charge and what is the lagging charge of the cardiac dipole?

leading charge: positive
lagging chard: negative

7

what limb lead is the most parallel to the cardiac dipole?

lead II

8

how does a lead look at the moving charge?

looks from the positive electrode to the wave coming towards it from the negative electrode

9

what direction does the depolarisation have to move in order for an upwards deflection?

depolarisation needs to be moving towards positive electrode
(ie positive electrode is looking at wave coming towards it)

10

what are PR, ST and TP intervals flat on an ECG?

because there is no moving wave
(ie no change in potential at that time)

11

how are augmented limb leads formed?

1 of the limb electrodes acts as the positive recording electrode and the other 2 are coupled together as teh negative reference electrode

12

what limb electrodes make up aVR?

positive electrode: RA
negative electrode: LA+LL

13

what limb electrodes makes up aVL?

positive electrode: LA
negative electrode: LL+RA

14

what limb electrodes make up aVF?

positive electrode: LL
negative electrode: LA+RA

15

why is the aVR recordings downwardly deflecting?

because the wave is manly moving away from the positive electrode

16

why is the limb lead II particularly good for looking at electrical activity?

because the wave is parallel to the lead axis and so has a great net potential difference so has well resolved waves

17

why is limb III not too good for looking at electrical activity?

because the wave is almost perpendicular to the lead axis so has a very small net potential difference so has poorly resolved waves

18

how many chest electrodes are there?

6

19

where is chest electrode 1 and what lead does it form?

1: 4th intercostal space, R of sternum
lead = V1

20

where is chest electrode 2 and what lead does it form?

2: 4th intercostal space, L of sternum
lead = V2

21

where is the chest electrode 3 and what lead does it form?

3: between 2 and 4
lead = V3

22

where is the chest electrode 4 and what lead does it form?

4: 5th intercostal space midclavicular line
lead = V4

23

where is the chest electrode 5 and what lead does it form?

5: 5th intercostal space anterior axillary line
lead = V5

24

where is the chest electrode 6 and what lead does it form?

6: 5th intercostal space mid-axillary line
lead = V6

25

what gives the negative reference electrode for the chest leads?

all 3 limb leads combines
(roughly the ecentre of the heart)

26

what happens to the limb leads if chest leads arent working?

nothing

27

what happens to the chest leads if the limb leads aren't working?

chest leads don't work either

28

what plane do the limb leads show?

frontal plane

29

what plane do the chest leads show?

horizontal plane

30

how long should the P wave be?

0.08- 0.10 seconds
(between 2/3 small boxes)

31

how long should the PR interval be?

0.12 - 0.2s
(between 3/5 small boxes)

32

what should the normal callibration of ECG be?

paper speed = 25mm/sec
10mm amplitude = 1mV

33

what is one small square on ECG paper?

1mm, 0.04s

34

what is one big square on ECG paper?

5mm, 0.2s

35

how many big squares and little squares are there per second?

5 big squares per second
25 small squares per second

36

how do you figure out the heart rate?

300/
(no.of big squares between QRS complexes)

37

what is the ECG rhythm strip?

a prolonged recording of lead 2 which allows you to detect rhythm distrubances

38

what is the step by step approach to analysing an ECG rhythm strip?

1. clarify patient
2. date/time of ECG
3. check calibration of the machine
4. is electrical activity present?
5. is the rhythm irregular or irregular?
6. what is the heart rate?
7. are there P waves present?
8. is the PR interval normal?
9. is each p wave followed by a QRS complex
10. is QRS duration normal
11. look for individual leads for changes

39

how would you tell if the cardiac rhythm is regular or irregular from a rhythm strip?

if rhythm is regular, QRS complexes occur at regular intervals

40

how can you calculate the heart rate from a rhythm strip if the rhythm is irregular?

count number of QRS complexes within 30 big squares and times that by 10

41

what can it mean if the PR interval is too long?

problem with AV conduction

42

what does it mean if each P wave is followed by a QRS complex?

sinus rhythm

43

how long should a QRS complex be?

less than 0.10 seconds
(less than 3 small boxes)