12-Lead ECG 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.

Electrode Placement

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 ECG leads are 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 III LA LL Inferior
aVR LA + LL RA None
aVL RA + LL LA Lateral
aVF RA + LA LL Inferior
V1 Septal
V2 Septal
V3 Anterior
V4 Anterior
V5 Lateral
V6 Lateral

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.

Comments

  1. Chris Kunce says

    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

    • EMTResource.com says

      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.

    • Jt says

      Chris

      I encourage you to try both ways. You will find that breast tissue does not cause changes in morphology or add artifact to the EKG. Lead placement is crucial and some breasts can force you to place some precordial leads closer to the stomach than the heart! Good luck.

  2. Jessica U says

    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!

    • EMTResource.com says

      Hi Jessica,

      We’re glad you found this article helpful and we appreciate the quote on your website. We wish you the best of luck in med school!

    • Marco A says

      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.

  3. Debbie Chabot says

    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?

      • EMTResource.com says

        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.

    • Jenny says

      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.

  4. Laurie Klimczyk MSN RN says

    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.

  5. Thomas Hood says

    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.

      • Natalie says

        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.

  6. Shree Ram Tiwari says

    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

  7. Martha says

    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.

    • Nani says

      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!

  8. Wendy Holder says

    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.

  9. Paul says

    What are the consequences if one mis place the chest leads like for example one puts v4,v5,v6 on the forth intercostal space?

    • EMTResource.com says

      Hi Paul,

      Superior (above the 5th ICS) or inferior (below the 5th ICS) misplacement of V4-V6 can lead to changes in wave shape and amplitude.

  10. jonathan says

    Nice source..can i just ask..why is there a need to unbuckle belts and remove coins/dimes from the pocket of the patient..thanks..

    • EMTResource.com says

      Hi Jonathan,

      Interesting question and we’ve never heard of this before. Our first thought was the metal might interfere with the ECG; however, after doing some research, we couldn’t find any sources stating that you need to unbuckle belts and/or remove coins from the patient’s pocket. As far as we know, this is unnecessary and shouldn’t have an impact on the ECG.

    • EMTResource.com says

      Hi Angie,

      It’s generally a good practice to remove or unstrap all bras to ensure proper placement of the precordial leads. As for watches and bracelets, these items should be okay and can be left on the patient.

  11. Garnet says

    I was taught by a Cardiologist that i can place RAL LAR on the back of the hands, and alos the other limb leads on each side of the stomac, Is this correct? I hate to over step a Dr.

  12. Kim Hicks says

    I was just wondering why you shouldn’t place any of the electrodes over bony prominences? Is it because the electrical impulse isn’t read as easily?

    • EMTResource.com says

      Hi Kim,

      Correct — Bone isn’t a good electrical conductor, so it’s best to avoid it. In addition, muscle movement can be increased when placing electrodes over bones. This movement can then cause a wandering baseline on the ECG.

  13. Jenni Hall says

    I too was shown that the limb leads can be placed on back of hands or shoulders and on each side of the stomach.
    can you clarify if this will cause a misleading interpretation?

  14. Jamie Welgan says

    I teach a medical assistant class and the students have a hard remembering the lead placement for 12 leads as well as Holter monitors. Any suggestions or mnemonics you’re aware of?

  15. Dee Layne says

    I am just wondering how accurate an ECG result is if the technician placing the leads failed to place leads below the waist? A diagnosis was made and treatment recommended based upon the reading done without lower extremity leads. How concerned should I be and would you recommend getting another test done properly or requesting a second opinion? Thank you so very much.

  16. rose lillo says

    good information here because it is hard to find this on the web- so many bad habits (as mispacement of ECG dots even among coronary care nurses!!)

  17. K says

    I am wondering if you have any suggestions for memorizing lead placement as well as the various rhythms for when i and taking ACLS and PALS. If you could e-mail me some suggestions i would greatly appreciate it.
    I also just started in a Cardiology position, and any information that you could give me would be awesome. Thank you. This is a great site!

  18. says

    Hi
    Excellent article-very concise and educational. I work for a company that can derive the 12-lead EKG (technically we can do 15-22 leads-posterior & right heart in Europe). using only 5 electrodes. V2 and limbs. Would you find this beneficial? We recently won the EMS World Expo Innovation Award. I’d be interested to hear your feedback. Thanks again! One other question – Above you state “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.” Do you have a reference for that? Thanks.

  19. Cariline says

    Hi, I am taking a course in EKG can you give me some advice on where the electrodes are place and ways to remember this doing my State Board in November. Thank you this site is very informative keep it up

  20. Shelia Booker says

    I currently work as a paramedic in the field and was taught if the patient has poor circulation in the legs you will not get an accurate 12 lead reading, to move the limb leads to the abdomen. Is this true? What does poor circulation have to do with a 12 lead reading?

  21. Theresa says

    Any suggestions for memorising various rhythums for when I do my ACLS/PALS.
    Thank you….this is a very helpful site…..lots of good tips.

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