ECG + interpretation of ECG

Question 1

what will a wave of depolarisation approaching a positive electrode cause? / wave of repolarisation heading away from a positive electrode?

Answer 1

an upwards going blip

Question 2

why is the p wave detected?

Answer 2

atrial depolarisation- because this occurs in the same direction of SLL II- wave of depolarisation going in direction of left leg

Question 3

how many standard limb leads are there and which one is the main one? what does it have?

Answer 3

3 SLLs, main one is II, has a negative electrode on RIGHT HAND and positive electrode on LEFT FOOT. commonly single out for HR& rhythm

Question 4

what does the PR interval show and how long should it be

Answer 4

it shows the time between atrial depolarisation & ventricular depolarisation, should be between 0.12 and 2seconds- between 3-5 small squares on ECG

Question 5

what does the QRS complex show and how long should it be

Answer 5

it shows ventricular depolarisation, should be less than 0.12 seconds - < 3 small squares on ECG

Question 6

what is the QT interval?

Answer 6

this is the time spent while the ventricles depolarise

Question 7

what does the ST segment show ?

Answer 7

the ventricles contracting and pumping blood

Question 8

why can atrial repolarisation not be seen?

Answer 8

it is masked by ventricular depolarisation. ventricular depolarisation involves more tissue depolarising much faster and therefore masks atrial depolarisation

Question 9

what do the 3 points in the QRS complex show?

Answer 9

Q- intraventricular septum depolarising left to right
R- rest of the ventricles depolarising from endocardial to epicardial surface
S- upper part of the inter ventricular septum depolarising

Question 10

why is the R wave bigger in SLL II?

Answer 10

because the wave of depolarisation follows the direction of the axis of SLL II

Question 11

why is the T wave positive?

Answer 11

the wave of repolarisation travels back up the heart and a wave of repolarisation that moves away from a positive electrode will cause a positive blip

Question 12

what happens to the R waves if the heart rotates or is hypertrophied?

Answer 12

the SLLs will be altered and R waves will be of different size

Question 13

what are the three augmented limb leads and what charge/where are they placed?

Answer 13

aVR- right arm positive
aVL- left arm positive
aVF- right foot positive (cross shape with arms)

Question 14

on what plane do the standard limb leads look at the spread of depolarisation?

Answer 14

frontal

Question 15

on what plane do the precordial leads look at the spread of depolarisation?

Answer 15

transverse

Question 16

what blip will V1 show and what blip will V6 show and where are they placed?

Answer 16

V1= negative blip/ 4th intercostal space to right of sternum 
V6= positive blip

Question 17

at what timing should the rhythm strip paper run?

Answer 17

25mm/s

Question 18

How do you interpret an ECG? (mnemonic)

Answer 18

A- any electrical activity?
R- rate 
I- irregular or regular
B- are the QRS complexes broad or narrow 
A- atrial activity?
R- relationship between QRS and p waves

Question 19

how do you measure rate from the rhythm strip?

Answer 19

measure the R-R interval and count how many there are in 30 large squares (6 seconds) and then multiply by 10
60-100 bpm= normal
< 60= bradycardia
>100 = tachycardia

Question 20

how do you check the rhythm?

Answer 20

line up a strip of paper along the rhythm strip and mark out 3-4 QRS complexes, then move this along 1-2 at a time and see if they correspond to your marks

Question 21

what is a STEMI?

Answer 21

ST- elevation MI - means that heart attack is very bad, with lots of dead tissue that has been affected from myocardial surface to epicardial surface

Question 22

what is a NSTEMI?

Answer 22

Non-ST elevation MI

Question 23

what does the relationship between p waves and QRS allow you to check?

Answer 23

heart block