ECG

Question 1

what would cause an upwards blip?

Answer 1

an approaching wave of depolarisation or a retreating wave of hyperpolarisation

Question 2

what does standard limb lead 2 measure?

Answer 2

from the left leg with respect to the right arm

Question 3

what causes the P wave (first blip)?

Answer 3

atrial depolarisation

Question 4

what causes the QRS complex?

Answer 4

ventricular depolarisation

Question 5

what causes the T wave?

Answer 5

ventricular repolarisation

Question 6

what does the PR interval tell you?

Answer 6

this is the time from atrial depolarisation to ventricular depolarisation and is due to transmission through the atrial ventricular node

Question 7

what is the QT interval?

Answer 7

this is the time spent while ventricles are depolarised, it varies with heart rate but is 0.42secs at 60 bpm

Question 8

why can atrial repolarisation not be seen by SLL2?

Answer 8

because it coincides with ventricular depolarisation. ventricular depolarisation involves a lot more tissue depolarising a lot aster swamping any signal from the repolarisation

Question 9

during ventricular depolarisation what depolarises first?

Answer 9

the interventricular septum depolarises from left to right away form the sll2 electrode.

Question 10

what causes the spike in the QRS complex?

Answer 10

the bulk of ventricular depolarisation from the endocardial to epicardial surface, this wave of depolarisation is towards sll2.

Question 11

what causes the small dip at 2 in sll2?

Answer 11

the upper part of the interventricular septum depolarising, there is not much tissue and it is away from the electrode

Question 12

why is the t-wave positive?

Answer 12

the action potential is longer in the endocardial cells than the epicardial cells so the wave of repolarisation runs in the opposite direction to the wave of depolarisation, which is away from the electrode of sll2 creating a positive blip.

Question 13

why is the r-wave bigger in the sll2 than 1 or 3?

Answer 13

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

Question 14

what are augmented limb leads recording?

Answer 14

from one limb lead with respect to the other two combined gives 3 perspectives on events in the heart

Question 15

what other perspective do the precordial leads?

Answer 15

they give you perspective but in the transverse plane

Question 16

on the precordial leads what lead would give a positive blip during depolarisation of the ventricles?

Answer 16

V6 on rib 7

Question 17

which precordial lead would give a negative blip during ventricle depolarisation?

Answer 17

V1 on rib4

Question 18

from how many angles do the limb look at the spread of depolarisation?

Answer 18

6 in the frontal plane

Question 19

at what speed should paper run at?

Answer 19

25mm/sec

Question 20

what size should the calibrating pulse be?

Answer 20

1 large square, 5mm

Question 21

what is the normal heart rate?

Answer 21

60-100 beats per min

Question 22

what is below 60 beats per minute called?

Answer 22

bradycardia

Question 23

what is above 100 beats per minute called?

Answer 23

tachycardia

Question 24

what is STEMI?

Answer 24

this is a ST elevated myocardial infarction

Question 25

what is NSTEMI?

Answer 25

this is a non-ST elevated infarction