12 Practical ECG Methods

Question 1

Describe the ECG pattern for one cardiac cycle

Answer 1

SA node depolarisation: P wave
AV node depolarisation: isoelectric line (delays signal transduction)
Bundle of His depolarisation: isoelectric line (rapid conduction)
Bundle branch: Q wave; downward (septal depolarisation)
Purkinje fibres (1): R wave (ventricular depolarisation)
Purkinje fibres (2): S wave (late ventricular depolarisation)
Fully depolarised ventricles: isoeletric line
Ventricular repolarisation: T wave

Question 2

Describe the placement of leads V1 - V6

Answer 2

V1: Right 4th intercostal space at the sternum
V2: Left 4th intercostal space at the sternum
V3: Between V2 and V3
V4: Left 5th intercostal space at midclavicular line
V5: Left 5th intercostal space at anterior axillary line
V6: Left 5th intercostal space at mid axillary line

Question 3

Describe 1) the location, 2) polarity and 3) planes of the leads

Answer 3

Lead I - III, aVL, aVR and aVF are on the limbs, V1-6 are chest leads

Lead I - III, aVL, aVR and aVF are coronal, V1-6 are transverse

Bipolar for Leads I - III, the rest are unipolar