ECG + interpretation of ECG Flashcards
what will a wave of depolarisation approaching a positive electrode cause? / wave of repolarisation heading away from a positive electrode?
an upwards going blip
why is the p wave detected?
atrial depolarisation- because this occurs in the same direction of SLL II- wave of depolarisation going in direction of left leg
how many standard limb leads are there and which one is the main one? what does it have?
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
what does the PR interval show and how long should it be
it shows the time between atrial depolarisation & ventricular depolarisation, should be between 0.12 and 2seconds- between 3-5 small squares on ECG
what does the QRS complex show and how long should it be
it shows ventricular depolarisation, should be less than 0.12 seconds - < 3 small squares on ECG
what is the QT interval?
this is the time spent while the ventricles depolarise
what does the ST segment show ?
the ventricles contracting and pumping blood
why can atrial repolarisation not be seen?
it is masked by ventricular depolarisation. ventricular depolarisation involves more tissue depolarising much faster and therefore masks atrial depolarisation
what do the 3 points in the QRS complex show?
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
why is the R wave bigger in SLL II?
because the wave of depolarisation follows the direction of the axis of SLL II
why is the T wave positive?
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
what happens to the R waves if the heart rotates or is hypertrophied?
the SLLs will be altered and R waves will be of different size
what are the three augmented limb leads and what charge/where are they placed?
aVR- right arm positive
aVL- left arm positive
aVF- right foot positive (cross shape with arms)
on what plane do the standard limb leads look at the spread of depolarisation?
frontal
on what plane do the precordial leads look at the spread of depolarisation?
transverse
what blip will V1 show and what blip will V6 show and where are they placed?
V1= negative blip/ 4th intercostal space to right of sternum V6= positive blip
at what timing should the rhythm strip paper run?
25mm/s
How do you interpret an ECG? (mnemonic)
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
how do you measure rate from the rhythm strip?
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
how do you check the rhythm?
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
what is a STEMI?
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
what is a NSTEMI?
Non-ST elevation MI
what does the relationship between p waves and QRS allow you to check?
heart block
