ECG Lead Placement
Illustrated electrode placement for 3-lead, 5-lead, and 12-lead ECG. IEC colour coding shown.
3-Lead — Monitoring Placement
Diagram is schematic — viewer's left = patient's right
3-Lead Monitoring
Three electrodes placed on the torso for continuous rhythm monitoring. Produces leads I, II, and III.
Right subclavicular space, below the right clavicle, medial third. Avoid bony prominences.
Left subclavicular space, below the left clavicle, medial third. Mirror of RA position.
Left lower chest or left iliac crest area. Maximise distance from RA/LA to improve signal quality.
Leads Produced
Lead I: LA − RA (lateral view)
Lead II: LL − RA (inferior view — most used for monitoring)
Lead III: LL − LA (inferior view)
5-Lead Monitoring
Adds RL (neutral/ground) and a single precordial (V) electrode. Produces leads I, II, III, aVR, aVL, aVF, and one chest lead.
Right subclavicular — same as 3-lead.
Left subclavicular — same as 3-lead.
Left lower chest — same as 3-lead.
Right lower chest / right iliac crest area. Neutral/ground electrode — reduces artefact. Does not contribute to tracings.
Placed at required chest position (commonly V1: 4th ICS right sternal border). Select on monitor for desired lead.
12-Lead ECG
Four limb electrodes (placed on distal extremities) and six precordial electrodes placed across the chest.
Limb Electrodes
Dorsal surface of right forearm, proximal to wrist. Avoid muscle bellies.
Dorsal surface of left forearm, proximal to wrist.
Medial surface of left lower leg, proximal to ankle.
Medial surface of right lower leg. Ground electrode only.
Precordial Electrodes (V1–V6)
| Lead | Position | Landmark |
|---|---|---|
| V1 | 4th ICS, right sternal border | Palpate angle of Louis → 2nd rib → count down |
| V2 | 4th ICS, left sternal border | Mirror of V1, left side of sternum |
| V3 | Between V2 and V4 | Midway between V2 and V4 |
| V4 | 5th ICS, left midclavicular line | Apex of heart region |
| V5 | Anterior axillary line (V4 level) | Same horizontal level as V4 |
| V6 | Midaxillary line (V4 level) | Same horizontal level as V4 and V5 |
Precordial (V1–V6) Chest Placement
Anatomical close-up — patient's right is on the left of the diagram
Palpate the sternal angle (angle of Louis) → slide finger to the 2nd rib → count down to 4th intercostal space, just right of the sternum.
Mirror of V1 directly across the sternum, same intercostal space.
No independent intercostal reference — placed geometrically midway between V2 and V4.
Apex region. Sets the horizontal level for V5 and V6 — all three sit at the same height.
Directly lateral to V4 along the anterior axillary line, same horizontal level.
At the midaxillary line, same horizontal level as V4 and V5.
Female Electrode Placement
V1 and V2 placement is identical to male. V3–V6 are placed under the breast tissue — gently lift the breast and apply the electrode directly against the chest wall beneath it. Never place electrodes on top of breast tissue as this degrades signal quality.
4th ICS at right and left sternal borders. Typically above breast tissue.
Midway between V2 and V4. May be under the medial breast — lift and place on chest wall.
All three placed under the left breast. Landmark positions are the same (5th ICS/MCL for V4; anterior and midaxillary for V5/V6) but the electrode must contact chest wall, not overlying tissue.
Lead Colour Conventions
IEC 60601-2-27 (International — used in SA, Europe, Aus)
AHA (USA)
Always verify lead colours on your specific monitor/cable set. Mnemonic (IEC limb): Read Your Green Book — Red, Yellow, Green, Black.
Clinical Disclaimer: Correct electrode placement is critical for accurate ECG interpretation. Always follow your service protocols and verify lead placement clinically.