ECGs

Question 1

Electrode placement

Answer 1

Red (Right arm), Yellow (left arm), Green (left leg), black (right leg)
V1 is IC4 left, V2 is IC4 right, V3 is between V2 and V4, V4 is ISC5 MCL, V5 is anterior axillary line level with L4, V6 is mid axillary line level with V4

Question 2

PR interval

Answer 2

Start of P wave to start of QRS

Question 3

QT interval

Answer 3

Start of QRS to end of T wave

Question 4

PR segment

Answer 4

End of P wave and Start of QRS (baseline).

This is delay at AV node only

Question 5

ST segment

Answer 5

End of QRS, start of T

Question 6

Paper time and voltage

Answer 6

Small squares are 0.04s and 0.1mv.
Larger squares are 0.2s
10 small squares is 1mV

Question 7

P wave

Answer 7

Atrial depolarisation. Should be <0.12 (3 small squares) in time. <0.25mv (2.5 small squares high)
Upright in Lead I, AvF, V3-V6

Question 8

PR interval

Answer 8

Atrial depolarisation (P wave) AND delay at AV node
Should be 0.12-0.20 s (3-5 small squares)

Question 9

QRS

Answer 9

0.5mV in 1+ limb lead, and >1mV in 1+ chest lead.
Should 3.0mV or less.
Positive in I, II, V4-V6
Negative in aVR, V1 and V2

Question 10

R’

Answer 10

Any subsequent positive wave that follows the R wave

Question 11

QT interval

Answer 11

Covers whole ventricular Action potential.

In males, <0.4 s, in females <0.44 seconds (11 small squares). Needs rate correcting (QTc).

Question 12

ST segment elevation/depression

Answer 12

Isoelectric until start of T wave, but 2mm elevation is normal in chest leads
Nor normally depressed >0.5mm

Question 13

T wave specifics

Answer 13

Normally rounded and asymmetrical. Aplitude is >0.2mV in V3 and V4.
Direction is the same as QRS in at least 5 limb leads.

Question 14

Axis deviation

Answer 14

LEft axis deviation: Lead 1 up and aVF down
Right axis deviation: lead 1 down and aVF points up
Extreme axis deviation: Lead 1 and aVF point downwards