How to do ecg – Orris AI

How to do ecg

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how to perform 12-lead ECG electrode placement technique steps

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Here is a complete, step-by-step guide to performing a 12-lead ECG, drawn from Roberts and Hedges' Clinical Procedures in Emergency Medicine and Pfenninger and Fowler's Procedures for Primary Care.

How to Perform a 12-Lead ECG

Overview

A 12-lead ECG records the heart's electrical activity from 12 different perspectives using 10 electrodes - 4 on the limbs and 6 on the chest. The 12 leads are divided into:

Frontal/limb leads: I, II, III, aVR, aVL, aVF (from the 4 limb electrodes)
Precordial leads: V1-V6 (the 6 chest electrodes)

Step 1 - Patient Preparation

Position the patient supine (flat). If they need the head elevated for comfort, note the angle so future ECGs match.
Arms at sides, legs flat and not touching each other.
Expose the chest and distal extremities; keep the rest covered to maintain dignity and prevent shivering (shivering causes tremor artifact).
Clean the skin at electrode sites with an alcohol swab. Shave hair if needed. Gentle abrasion with fine-grit sandpaper can reduce noise and improve contact quality.

Step 2 - Machine Settings

Turn on the ECG machine. Standard settings:
- Paper speed: 25 mm/sec
- Amplitude: 1 mV = 10 mm
Perform the ECG away from powerful electrical equipment (motors, X-ray machines) to avoid interference.

Step 3 - Limb Electrode Placement

Each electrode is color-coded:

Location	Label	Color
Right arm	RA	White
Left arm	LA	Black
Left leg	LL	Red
Right leg (ground)	RL	Green

Traditionally placed on wrists and ankles, but placing more proximally (upper arms/thighs) reduces motion artifact - both are acceptable.

Step 4 - Precordial (Chest) Electrode Placement

Place in this order:

Lead	Color	Position
V1	Red	4th intercostal space (ICS), right sternal border
V2	Yellow	4th ICS, left sternal border
V4	Blue	5th ICS, mid-clavicular line (place V4 before V3)
V3	Green	Halfway between V2 and V4
V5	Orange/Tan	Anterior axillary line, same horizontal level as V4
V6	Violet	Mid-axillary line, same horizontal level as V4 and V5

Landmark tip: Find the sternal angle (junction of manubrium and sternum body) - this is just above the 2nd ICS. Count down from there to the 4th ICS. In men, the nipple typically overlies the 4th ICS at the mid-clavicular line. V4, V5, and V6 must all be in the same horizontal plane.

Use only bony landmarks for consistent, reproducible placement. - Pfenninger and Fowler's Procedures for Primary Care

Step 5 - Acquire the Tracing

Ensure the patient is relaxed and still (muscle movement causes artifact).
Press record. The machine prints leads I through aVF (frontal) and V1-V6 (precordial).
If dysrhythmia is suspected, obtain an extended rhythm strip.
Best leads for monitoring:
- Ischemia: V5 (most sensitive)
- Rhythm: Lead II
- If 3 channels available: aVF, V2, V5

Step 6 - Remove Electrodes and Document

Remove electrodes and dispose of them.
Clean the skin where electrodes were attached.
Label the ECG with patient name, date, time, and any relevant clinical notes (e.g., chest pain onset time, patient position if not flat).

Common Errors to Avoid

Limb lead reversal (most common error): RA/LA swap causes inverted lead I and abnormal axis. Suspect it when the computer flags new right axis deviation.
V1/V3 reversal: Causes abnormal R-wave progression and T-wave inversion in V3.
Incorrect ICS counting: Always count from the sternal angle (2nd ICS) down - never estimate.
Poor skin contact: Leads to a noisy, artifact-ridden tracing. Re-clean and re-apply.
Movement/shivering: Ensure patient is comfortable and warm.

Sources: Roberts and Hedges' Clinical Procedures in Emergency Medicine; Pfenninger and Fowler's Procedures for Primary Care, 3rd ed.

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