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ECG electrode lead placement positions anatomical landmarks diagram

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Here is a complete guide to ECG electrode positions and locations, with images from authoritative sources:

12-Lead ECG: Electrode Positions & Locations

A standard 12-lead ECG uses 10 electrodes total - 4 limb electrodes and 6 precordial (chest) electrodes - to generate 12 electrical "views" of the heart.

PART 1: Limb Leads (4 electrodes)

12-lead ECG full electrode placement showing limb and chest leads
ElectrodePosition
RA (Right Arm)Right forearm / wrist
LA (Left Arm)Left forearm / wrist
RL (Right Leg)Right lower leg, proximal to ankle (ground electrode)
LL (Left Leg)Left lower leg, proximal to ankle
These 4 electrodes generate 6 frontal plane leads: I, II, III, aVR, aVL, aVF.
Note: Electrodes may be moved more proximally (e.g., upper arm/thigh) if needed due to amputation or injury, with a notation on the ECG. The Mason-Likar configuration moves limb leads to the torso for ambulatory monitoring.

PART 2: Precordial Leads (V1-V6) - Chest Electrodes

Anatomical Landmarks Diagram

Chest landmarks showing intercostal spaces, sternal angle, and reference lines for V4-V6

Precordial Lead Positions

Precordial V1-V6 electrode positions on chest skeleton diagram
V1-V6 placement on real patient chest with sternal angle and 4th ICS landmarks
V1-V6 chest leads overlaid on heart anatomy showing relationship to heart chambers
LeadExact PositionWhat It "Looks At"
V14th intercostal space (ICS), right sternal borderSeptal / RV
V24th ICS, left sternal borderSeptal / RV
V3Midway between V2 and V4 (diagonal)Anterior wall
V45th ICS, midclavicular lineAnterior / Apex
V5Anterior axillary line, same horizontal level as V4Lateral wall
V6Midaxillary line, same horizontal level as V4 & V5Lateral wall
Key: V4, V5, and V6 must all be on the same horizontal level - not following the curve of the ribs, which would displace V5 and V6 superiorly.

PART 3: How to Find the 4th Intercostal Space

  1. Palpate the sternal notch (top of the sternum) - move fingers downward
  2. Find the sternal angle (Angle of Louis) - the transverse bony ridge ~5 cm below the sternal notch, where the manubrium meets the sternal body
  3. Immediately lateral and inferior to the sternal angle = 2nd intercostal space
  4. Count down two more spaces = 4th intercostal space (where V1 and V2 go)
  5. For V4: from the 4th ICS on the left, move diagonally down-out to the 5th ICS at the midclavicular line

PART 4: What Each Region of Leads Represents

RegionLeadsCoronary Artery Territory
InferiorII, III, aVFRight coronary artery (RCA)
LateralI, aVL, V5, V6Left circumflex artery (LCx)
AnteriorV1-V4Left anterior descending (LAD)
SeptalV1, V2LAD (septal branches)
Right VentricularV1, (V3R, V4R)RCA

PART 5: Special Lead Placements

  • Right-sided ECG (V3R-V6R): Mirror image placements on the right chest - used to detect right ventricular MI
  • Posterior leads (V7-V9): Placed at posterior axillary line, tip of scapula, and paravertebral line at the same horizontal level as V4-V6 - used to detect posterior MI
  • Pediatric: Standard V1-V6 plus V3R and V4R (right-sided leads) are routinely added
Source: Roberts and Hedges' Clinical Procedures in Emergency Medicine - Electrode Placement; LITFL ECG Lead Positioning
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