Lead positioning

3-electrode system
– Uses 3 electrodes (RA, LA and LL).
– Monitor displays the bipolar leads (I, II and III)
– To get best results – Place electrodes on the chest wall equidistant from the heart (rather than the specific limbs)
5-electrode system
– Uses 5 electrodes (RA, RL, LA, LL and Chest)
– Monitor displays the bipolar leads (I, II and III)
– AND a single unipolar lead (depending on position of the brown chest lead (positions V1–6))
12-lead ECG
– 10 electrodes required to produce 12-lead ECG.
– – Electrodes on all 4 limbs (RA, LL, LA, RL)
– – Electrodes on precordium (V1–6)
– Monitors 12 leads (V1–6), (I, II, III) and (aVR, aVF, aVL)
– Allows interpretation of specific areas of the heart
– – Inferior (II, III, aVF)
– – Lateral (I, aVL, V5, V6)
– – Anterior (V1–4)

The ECG is one of the most useful investigations in medicine. Electrodes attached to the chest and/or limbs record small voltage changes as potential difference, which is transposed into a visual tracing

ECG electrode system

ECG electrode system


ECG Academy Videos

The ECG Lead

The Limb Leads

The Precordial Leads

Further Reading

Author Credits

  • Mike Cadogan
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