# 12-lead ECG acquisition & placement

Recognize when a 12-lead is indicated, place electrodes at the correct landmarks, acquire and transmit the tracing, and avoid delaying urgent care.

Population: All patients. Scope: BLS / ALS.
Status: draft. Draft OCEMS source summary.
Summary updated: 2026-09-16.
Source checked: 2026-09-16.
Source version: PR-105 revised September 10, 2019 and implemented April 1, 2020. B-030 implemented October 1, 2009.
Canonical page: https://www.ocmedic.com/guides/twelve-lead-ecg/

Draft independent OC Medic summary. Does not replace the complete policy, current system notices, or clinical judgment.

## A normal tracing does not rule out acute MI

- Do not delay stabilization, pacing, cardioversion, defibrillation, or transport to obtain a 12-lead.
- A normal tracing or one negative for STEMI does not rule out acute MI or serious angina.
- Machine interpretation may be unreliable with paced rhythms, bundle branch blocks, and some tachycardias; tell the base hospital when those rhythms are present.
- Base-hospital contact is required when a patient refuses BLS or ALS transport after a field 12-lead.

## Source documents

- [PR-105 — 12-Lead Electrocardiography](https://www.ochealthinfo.com/sites/hca/files/import/data/files/12406.pdf)
- [B-030 — 12-Lead EKG Placement Procedure](https://www.ochealthinfo.com/sites/hca/files/import/data/files/12433.pdf)

## Recognize an indication

- Obtain a 12-lead when a cardiac event is suspected, including atypical presentations. Examples include unexplained chest discomfort; cardiac history, tobacco use, hypertension, or diabetes with chest discomfort, dyspnea, or unexplained nausea/vomiting; radiating pain; unexplained diaphoresis; syncope; significant bradycardia; or unexplained tachycardia.
- In a patient over 45, acute anxiety or generalized weakness may represent a cardiac presentation even without classic pain. For unexplained tachycardia, PR-105 says to consider a tracing at 100-130/min and requires it at 130/min or more.
- BLS personnel may place electrodes on any patient as directed by on-scene ALS personnel.

## Stabilize first

- Complete the initial assessment and stabilizing treatment before acquisition. Do not delay time-critical care to obtain a 12-lead.
- If arrest, acute respiratory failure, systolic BP below 90, altered consciousness, or another severe condition makes delay unsafe, acquire the tracing at the incident location or in the vehicle immediately before transport begins.

## Prepare skin & place electrodes

1. Expose only what is needed, prepare skin with alcohol, and remove body hair as needed. For a female patient, use the dorsal surface of the hand to move tissue when necessary; do not place chest leads over breast tissue.
2. Place V1 at the right fourth intercostal space and V2 at the left fourth intercostal space.
3. Place V4 at the left fifth intercostal space on the midclavicular line, then place V3 halfway between V2 and V4.
4. Place V5 level with V4 at the anterior axillary line and V6 level with V5 at the midaxillary line. Place limb leads on the upper arms and lower abdomen or legs.

## Acquire, transmit & document

- Acquire the tracing according to the monitor manufacturer and relay the interpretation to the base hospital when indicated. Transmit positive or suspected acute-MI tracings before arrival at the receiving cardiovascular center.
- Document that the 12-lead was obtained and record the interpretation. Transmit the tracing from the field and attach or upload a copy to the prehospital care record.
- Leave electrodes in place unless removal is directed. If defibrillation or synchronized cardioversion is needed, position pads without covering electrodes, removing electrodes if necessary.