Reference
12-lead placement.
Correct lead placement is the difference between a diagnostic tracing and a missed STEMI.
Limb leads
- RA (white): right shoulder or wrist
- LA (black): left shoulder or wrist
- RL (green): right lower abdomen or ankle
- LL (red): left lower abdomen or ankle
- Mnemonic: "smoke over fire, snow over grass" (LA black over LL red; RA white over RL green).
Precordial (chest) leads
- V1: 4th ICS, right sternal border
- V2: 4th ICS, left sternal border
- V4: 5th ICS, midclavicular line (place V4 before V3)
- V3: midway between V2 and V4
- V5: anterior axillary line, horizontal with V4
- V6: midaxillary line, horizontal with V4
Right-sided leads (V4R)
Mirror V4 to the right chest: 5th ICS, right midclavicular line. Run on any inferior STEMI. ST elevation in V4R = RV infarct — hold nitro, give fluids for hypotension.
Posterior leads (V7–V9)
- V7: posterior axillary line, level with V6
- V8: midscapular line, level with V6
- V9: left paraspinal border, level with V6
Consider when V1–V3 show ST depression with tall R waves — a posterior wall MI you'd otherwise miss.
Which lead sees which wall?
- Inferior: II, III, aVF (RCA)
- Septal: V1, V2 (LAD)
- Anterior: V3, V4 (LAD)
- Lateral: I, aVL, V5, V6 (LCx)
- Posterior: reciprocal V1–V3 (RCA or LCx)
Frequently asked
- Where does V1 go?
- 4th intercostal space at the right sternal border. V2 sits opposite V1 at the left sternal border.
- Where do V4, V5, and V6 go?
- V4: 5th intercostal space, midclavicular line. V5 and V6 are horizontally in line with V4 at the anterior axillary and midaxillary lines.
- When do I add V4R and posterior leads?
- V4R on any inferior STEMI to rule out right-ventricular infarct before nitro. V7–V9 for suspected posterior MI (ST depression V1–V3 with tall R waves).
For educational and exam-preparation use only. Not medical advice.