12 Lead ECG / Cable / Electrode Placement (Position)
12 Lead ECG Position and Placement
12 Lead ECG Placement provides a whole representation by deriving and recording the heart’s electrical activity through 12 different perspectives.
Even though it is named as 12 lead ECG, it requires placement of 10 electrodes on the patient body.
The blog highlights on
1. 12 lead ecg meaning
2. Whom should receive 12 lead ecg ?
3. 12 lead ecg standard position and placement
4. Eithoven's triangle
5. 12 lead ecg color code
6. 12 lead ecg mnemonic
7. Skin preparation
8. Patient position
9. Reduce Artifacts
10. Electrode Application
1. Why is it called a 12 lead ECG with 10 leads?
Usually, An ECG reading requires 10 electrodes. Certain electrodes are included up as 2 pairs, thus paving the way for 2 leads.
Thus, it is named as the 12 lead ecg as the 10 electrodes provide 12 perspectives of the heart's electrical activity at various angles.
The term “lead” is not regarded as the wires which connect the ecg machine with the patient. However, To give you a bigger picture, A lead ECG refers to the various viewpoints of heart’s activity.
Each and every lead has a name to it.
The term “ electrode” refers to the self sticky patches / pads that stick to the patient’s skin. These electrodes are connected to the ecg machine via lead wires.
2. Whom should receive this 12 lead ECG ?
12 Lead ECG Testing is mainly used for cardiac ischemia screening of the patients (in particularly, (STEMI) ST- elevation myocardial infarction).
The several symptoms that lead to the undertaking of the this Ecg testing are
- Shortness of breath
- Palpitations
- Sudden chest pains
- Dizziness
- Cardiac Arrest
3. 12 Lead ECG Standard Position and Placement:
The 12 lead ecg placement is as follows
Chest Precordial Electrodes:
C1 -4th intercoastal space (Right Sternal Edge)
C2-4th intercoastal space (Left Sternal Edge)
C3- Midway between V2 and V4
C4- 5th intercoastal space - MidCavicular space
C5- Left Anterior Axillary Line, same horizontal level as V4
C6-Left Mid Axillary Line, same horizontal level as V4 and V5
Limb Electrodes:
R, L, N, F - They must be attached to the arms and legs which are proximal to the wrist and ankle.
There are 2 divisions namely vertical plane (also known as Frontal Leads) and horizontal plane (also known as Transverse Leads) upon which the ecg readings are performed.
Heart’s Vertical Plane (Frontal Leads) :
The 12 ecg lead position and groupings for Heart’s vertical plane are
- Lead I, II and III
- aVR, aVL and aVF (Augmented Vector Right, Augmented Vector Left, Augmented Vector Foot)
The ECG machine uses the 4 limb electrodes in order to provide 6 limb viewpoints.
Horizontal Plane (Transverse Leads):
By utilizing the 6 chest precordial electrodes, it offers 6 viewpoints of the heart's electrical activity.
- V1, V2, V3, V4, V5, V6
Bipolar Leads namely Lead I, II and III are used to measure the electrical potential between the positive and negative electrodes.
Unipolar Leads namely aVR, aVL & aVF , V1, V2, V3, V4, V5, V6 uses a positive electrode and other electrodes serve as a negative electrode.
According to the society for Cardiological Science and Technology (SCST) , For women / female patients, the V4, V5, V6 leads are to placed under the left breast when the breast tissue covers the placement area.
4. 12 lead Ecg Einthoven’s Triangle:
Einthoven’s Triangle works on the principle where not only does RA, LA, LL records the heart’s electrical activity corresponding to themselves through aVR, aVL & aVF. In addition, they relate to each other to form Leads I (RA to LA), Lead II (RA to LL) and Lead III (LA to LL).
This Einthoven’s Triangle is named after William Einthoven.
Lead I is recorded using LA being the positive electrode and RA being the negative electrode.
Lead II is recorded using LL being the positive electrode and RA being the negative electrode.
Lead III is recorded using LL being the positive electrode and LA being the negative electrode.
aVR is recorded using the RA being positive electrode and LL+ LA being the negative electrode
aVL is recorded using the LA being the positive electrode and RA+ LL being the negative electrode
aVF is recorded using the LL being the positive electrode and RA+ LA being the negative electrode.
Actually, RL serves as a grounding electrode to reduce unwanted noises / interferences.
5. 12 Lead ECG Color Coding:
To know more about different ecg leads color code , check here.
6. 12 Lead ecg placement Mnemonic:
One can use the 12 lead ecg placement mnemonic as follows :
For AHA system of 4 ecg electrode placement, one could use
Smoke over fire ( Black lead followed by Red lead) - Left Arm and leg
Snow over grass ( White lead followed by Green lead) - Right Arm and leg
For IEC system of 4 ecg electrode placement, one could use
Ride Your Green Bike - Red (right arm), Yellow (left arm), Green (Foot) Black (Neutral)
7. Skin Preparation:
Before the placement of lead electrodes, the skin preparation comes in.
As you know, the skin is the poor conductor of electricity.
For achieving the best ECG results and quality, Skin resistance plays an vital role in such cases.
- Remove excessive hair and oil from the skin.
- Wipe the skin with water / non- alcohol swabs to remove the oil. (Alcoholic wipes hinder the heart’s electrical activity )
- Inorder to increase the capillary blood flow of the tissue , the skin must be dried and free from dead cells.
- Make sure that the patient body is not sweating.
- Ensure that the electrode is placed in contact with the skin.
8. Patient Position:
- Positioning the patient in Semi-Fowler’s or Supine position are the best positions for optimal results. Just incase, when the patient cannot placed in both positions.
- Make sure that the patient does not cross the legs as it affects the signals.
- Make certain that Electrical / Electronic devices should be kept away from the patient.
9. Reduce the Artifacts:
- Ensure that the connection between the ecg machine and patient cable is secure.
- Check for any ECG Cables running close to metallic foreign objects.
- Check for any cable damage/ cracks. It is highly recommended to replace the cables, once damages on them are inspected.
- Keep away the electrical/ electronic equipment from the patient area.
10. Electrode Application:
Electrode misplacement commonly occurs while placing the ecg electrodes. 4.0% and 0.4%of Ecg recordings in ICU and cardiac outpatient clinics are found to be electrode misplacement.
- Make sure the electrode gel is moist.
- Never use a dry electrode gel as it could affect the ecg signals.
- Do not place the electrode on body areas with muscle movements.
- It is important to shave the patient’s hair that interferes with the application of electrode.
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Summary : The above guide is to educate, inform and help the users, technicians in placing the electrode/cable combination on human subject in a Simplified ideal way. Please feel free to respond back to us with suggestions to info@biometriccables.com .