If you are a patient, this page is for technician exam prep and is not a way to interpret your own EKG. Ask your clinician about your results, or read MedlinePlus on electrocardiograms.
Educational exam prep, not medical advice. This page teaches what certification exams test. Follow your facility’s policies, your supervising clinician and the manufacturer’s instructions in practice. If you are a patient with a health question, talk to your clinician or see MedlinePlus.
Precordial (chest) leads
| Lead | Location |
|---|---|
| V1 | 4th intercostal space, right sternal border |
| V2 | 4th intercostal space, left sternal border |
| V3 | Midway between V2 and V4 |
| V4 | 5th intercostal space, left midclavicular line |
| V5 | Left anterior axillary line, same horizontal level as V4 |
| V6 | Left midaxillary line, same horizontal level as V4 |
Limb electrodes (AHA colors)
| Electrode | AHA color | Placement |
|---|---|---|
| RA | White | Right arm/wrist or upper arm |
| LA | Black | Left arm |
| RL | Green | Right leg (ground) |
| LL | Red | Left leg |
Errors the exam tests
- Reversed arm leads (RA/LA): lead I becomes inverted - a classic question.
- V1/V2 placed too high (2nd-3rd intercostal space) distorts the QRS in those leads.
- Artifact: patient movement, shivering or poor skin prep; clean and dry skin, place electrodes on flat, non-bony areas.
- Find the 4th intercostal space by locating the sternal angle (angle of Louis), which sits at the 2nd rib, then counting down.
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Frequently asked questions
Where does V1 go?
Fourth intercostal space at the right sternal border.
Where is V4 placed?
Fifth intercostal space at the left midclavicular line.
What happens if RA and LA are reversed?
Lead I appears inverted, among other changes.
Sources
- AHA/ACCF/HRS - Recommendations for the Standardization and Interpretation of the ECG, Part I (Circulation 2007) (accessed 2026-09-23)
- NHA - CET Test Plan (2017 job analysis) (accessed 2026-09-23)
- StatPearls (NCBI Bookshelf) - Electrocardiogram (accessed 2026-09-23)