12-Lead ECG Placement



Electrode Placement

The 12-lead ECG is a vital tool for EMT’s and Paramedics in both the prehospital and hospital setting. It is extremely important to know the exact placement of each electrode on the patient. Incorrect placement can lead to a false diagnosis of infarction or negative changes on the ECG.

12-lead-ecg-placement
Electrode Placement
V1 4th Intercostal space to the right of the sternum
V2 4th Intercostal space to the left of the sternum
V3 Midway between V2 and V4
V4 5th Intercostal space at the midclavicular line
V5 Anterior axillary line at the same level as V4
V6 Midaxillary line at the same level as V4 and V5
RL Anywhere above the ankle and below the torso
RA Anywhere between the shoulder and the elbow
LL Anywhere above the ankle and below the torso
LA Anywhere between the shoulder and the elbow

Electrode Misplacement

  • Up to 50% of cases have the V1 and V2 electrodes in a more superior location, which can mimic an anterior MI and cause T wave inversion.
  • Up to 33% of cases have the precordial electrodes (V1-V6) inferiorly or laterally misplaced, which can alter the amplitude and lead to a misdiagnosis.

Electrode Reversal

  • RA/LA Reversal: Lead I is inverted, Lead II and III are reversed, aVR and aVL are reversed
  • RA/RL Reversal: Lead II shows isolated asystole, aVF and aVR are identical
  • LA/LL Reversal: Lead III is inverted, aVL and aVF are reversed

Lead Groups

The 12-lead ECG is grouped into two electrical planes. The frontal leads (Lead I-III, aVR-F) view the heart from a vertical plane, while the transverse leads (V1-V6) view the heart from a horizontal plane.

ecg-lead-planes
Lead (-) Electrode (+) Electrode View of Heart
Lead I RA LA Lateral
Lead II RA LL Inferior
Lead II LA LL Inferior
aVR LA + LL RA None
aVL RA + LL LA Lateral
aVF RA + LA LL Inferior

12-Lead Explained

One of the most common questions regarding a 12-lead ECG is why there are only 10 electrodes. It’s important to fully understand what the term “lead” actually means. A lead is a view of the electrical activity of the heart from a particular angle across the body. Think of a lead as a picture of the heart and the 10 electrodes give you 12 pictures. In other words, a lead is a picture that is captured by a group of electrodes.

Reducing Artifact

The heart’s electrical signal is very small and unfortunately this can be combined with other signals of similar frequency to create artifact. It’s not uncommon for 12-lead ECG’s to have some form of artifact; however, it’s important to try to reduce any interference to ensure an accurate ECG. Below is a list of guidelines that will help reduce artifact when performing ECG’s.

Patient Positioning

  • Place the patient in a supine or semi-Fowler’s position. If the patient cannot tolerate being flat, you can do the ECG in a more upright position.
  • Instruct the patient to place their arms down by their side and to relax their shoulders.
  • Make sure the patient’s legs are uncrossed.
  • Move any electrical devices, such as cell phones, away from the patient as they may interfere with the machine.

Skin Preparation

  • Dry the skin if it’s moist or diaphoretic.
  • Shave any hair that interferes with electrode placement. This will ensure a better electrode contact with the skin.
  • Rub an alcohol prep pad or benzoin tincture on the skin to remove any oils and help with electrode adhesion.

Electrode Application

  • Check the electrodes to make sure the gel is still moist.
  • Do not place the electrodes over bones.
  • Do not place the electrodes over areas where there is a lot of muscle movement.

Visit the ECG section to learn how to interpret 12-lead ECG’s and identify the different types of heart rhythms.


20 thoughts on “12-Lead ECG Placement

  1. Chris Kunce

    Another paramedic placed leads directly over pts breast instead of under breast..
    says less artifact. Is that ok for placement? I’ve never heard of it before

    August 5, 2013 at 11:33 am
    1. EMTResource.com

      Hi Chris,

      We’ve also encountered this in the field a few times; however, the AHA recommends that precordial electrodes are placed under the breast tissue on female patients. It’s important the electrodes are placed in the proper anatomical position and this can be difficult when placing above the breast. In addition, it’s unlikely that an ECG with electrodes above the breast would be as accurate or reproducible since breast tissue is prone to movement.

      August 5, 2013 at 3:29 pm
  2. Thank you so much!!! I’ve been puzzling over why there are only 10 electrodes in a 12 lead ECG for hours! You explain it much better than my med school book does… I quoted your article on my site and credited you, hope it will clear up the confusion for other confused medical students like me!

    August 8, 2013 at 1:45 pm
    1. EMTResource.com

      Hi Jessica,

      I’m glad you found this article helpful and we appreciate the quote on The Confused Medical Student. We wish you the best of luck in med school! :)

      August 8, 2013 at 4:58 pm
  3. REBECCA ONUOHA

    please i still find it difficult locating the V1 and V2 IN A WOMAN

    August 19, 2013 at 5:45 am
    1. Marco A

      Find the bottom of the sternum then place two fingers horizontally superior to that. Then from the top of those two fingers go horizontally to the patient’s right until you feel a rib, which should be the 5th rib. The space directly superior to the 5th rib is the 4th intercostal space where you place V1 slightly lateral to the Sternum and not touching the sternum. Then Place V2 directly opposite on the patient’s left side of the sternum.

      January 24, 2014 at 10:31 pm
  4. Debbie Chabot

    Do the electrode tabs (we’re using alligator clamps) all have to face the same direction (ie with the tab attachment to the alligator facing down)? One MA puts the leg tabs towards the head so the wires don’t pull. Not sure if this makes a difference?

    August 19, 2013 at 1:32 pm
    1. Debbie Chabot

      BTW: excellent article, great tool for teaching.

      August 19, 2013 at 1:33 pm
    2. EMTResource.com

      Hi Debbie,

      Great question and thank you for the compliment. As far as we know, the electrodes do not have to face the same direction. In fact, the MA’s placement technique is actually a good idea since it’s preferred to have less tension on the wires. This allows for a better electrode connection and keeps the alligator clips from slipping.

      August 19, 2013 at 1:50 pm
  5. Imbwae meshach

    Good article with points that are hitting the nail on the head. Educative.

    August 30, 2013 at 1:07 pm
  6. Laurie Klimczyk MSN RN

    As an educator I have referred individuals to your link because it is explained in such simple terms. I am wondering if you would consider adding education on placement for right sided EKGs. Thank you.

    September 2, 2013 at 12:29 pm
    1. EMTResource.com

      Thanks, Laurie! Yes, this is definitely something we can start working on.

      September 5, 2013 at 12:50 pm
  7. Jenny

    Debbie, I am an MA student graduating this week, and I was taught that the electrode tabs on the legs point toward the patient’s head, and that all other tabs point downward towards the toes. This helps with the wires not pulling and making the tabs come off the patient, and I was told it also helps the EKG have a better read. I don’t know if these are the actual reasons why, but this is how I place electrodes when I do EKGs.

    September 16, 2013 at 10:04 am
  8. Thomas Hood

    I am actually getting ready to start a medic course soon i am wondering if you have any suggestions for memorizing lead placement as well as the various rythms for when i amd taking ACLS and PALS. If you could e-mail me some suggestions i would greatly appreciate it.

    October 10, 2013 at 9:21 am
    1. EMTResource.com

      Hi Thomas,
      That’s great news and we just sent you an e-mail with some tips and suggestions! :)

      October 10, 2013 at 2:11 pm
      1. Natalie

        I am in the same situation as Thomas Hood. Could I please request similar tips and suggestions regarding EKG lead placement and interpretations? I sincerely appreciate it.

        December 8, 2013 at 8:09 pm
  9. Shree Ram Tiwari

    It was nicely described simply and clearly.Most of my paramedics get confused and forget easily.i will recommend them this useful site.thank you

    October 15, 2013 at 10:25 am
  10. Martha

    I have recently finish a course as a EKG Technician. Now it is job hunting time. Every place I have look want 12-24 month experience. Do you have any ideal or where I can go to get work experience or what I might ask to get employment. I would be so happy.

    October 21, 2013 at 3:23 am
    1. Nani

      Martha, hopefully you have found employment at this point. If you are still looking, you may want to try a temp agency. They may be able to help place you someplace for a bit in order to gain the required experience. Best of luck to you!

      December 9, 2013 at 11:08 pm
  11. Wendy Holder

    Apparently incorrect lead placement is occurring frequently in the primary care physician’s office also. I recently had an EKG done and was referred to a cardiologist all due to poor tech. I also paid copays, & the ins. company paid for unnecessary medical expense. I will be in contact with the PCP to report this mishap & suggest some remedies to avoid what happened in the future.

    December 28, 2013 at 12:50 pm

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