6. ECG

Question 1

What changes would you see on an ECG from someone with LV hypertrophy?

Answer 1

Taller R wave

Question 2

What does the Q wave represent?

Answer 2

Depolarisation of the inter ventricular septum , left to right.

Question 3

Why does the Q wave cause a downward deflection?

Answer 3

Movement obliquely away from the apex

Question 4

What does the S wave represent, why does it produce a downwards deflection?

Answer 4

Depolarisation to the base of the ventricles, moves away from the apex.

Question 5

What does the T wave represent?

Answer 5

Ventricular repolarisation

Question 6

Why is the T wave an upwards deflection?

Answer 6

Repolarisation away from the apex

Question 7

How many electrodes are used in a 12-lead ECG?

Answer 7

10 electrodes:
4 limb
6 chest

Question 8

How many views does a 12 lead ECG produce?

Answer 8

12

Question 9

What plane do the limb leads display?

Answer 9

Coronal plane

Question 10

What are the 6 limb leads?

Answer 10

Unipolar: aVR, aVF, aVL
Bipolar: I, II,III

Question 11

Which leads look at the inferior surface of the heart?

Answer 11

II, III and aVF

Question 12

Which leads look at the left side of the heart?

Answer 12

I and aVL

Question 13

Which plane do the chest leads show?

Answer 13

Transverse

Question 14

What are the 6 chest leads?

Answer 14

V1-V6

Question 15

Which chest leads are the septal leads?

Answer 15

V1 and V2

Question 16

Which chest leads are the anterior leads?

Answer 16

V3 and V4

Question 17

Which chest leads are the lateral leads?

Answer 17

V5 and V6

Question 18

How many seconds does 1 small square on an ECG machine represent?

Answer 18

0.04 seconds

Question 19

How many seconds does 1 large square represent?

Answer 19

0.2 seconds

Question 20

How would you calculate the HR using an ECG if the rhythm was irregular?

Answer 20

Count the number of QRS complexes in 30 large squares (6 seconds) then x 10.

Question 21

How would you calculate the HR using an ECG if the rhythm was regular?

Answer 21

300/ number of large boxes between R peaks

Question 22

What is the normal length of the PR interval?

Answer 22

0.12-0.20 seconds (3-5 small boxes)

Question 23

What is the normal length of QRS interval?

Answer 23

<0.12 seconds (< 3 small boxes)

Question 24

What is a normal length of a QT interval?

Answer 24

11-12 small boxes (corrected for HR)

Question 25

How would you measure the QT interval?

Answer 25

Start of Q-wave to end of T-wave

Question 26

How would you measure PR interval?

Answer 26

Start of P interval to start of Q wave

Question 27

How would you measure the ST segment?

Answer 27

End of S wave to start of T wave

Question 28

What does a widened QRS suggest?

Answer 28

Ventricular depolarisation that are not initiated by normal conductance mechanism

Question 29

What does a prolonged PR interval suggest?

Answer 29

Slow conduction from atria to ventricle - first degree heart block

Question 30

What does a prolonged QT interval suggest?

Answer 30

Prolonged repolarisation of the ventricles, this can lead to arrythmias.

Question 31

What colour are the limb electrodes?

Answer 31

Ride your green bike
Right arm = red
Left arm = yellow
Left leg = green
Right leg = black

Question 32

Where should the chest leads be attached to?

Answer 32

V1 right 4th intercostal
V2 left 4th intercostal
V3 Midway between V2 and V4
V4 5th IC space in mid-clavicular line
V5 5th IC space anterior axillary line
V6 5th IC space mid-axillary line