12-Lead Placement: EKG Electrode Positions, V1 to V6

A 12-lead ECG is ten electrodes producing twelve views of the heart. Four go on the limbs and six go across the chest. The machine assumes every one of them is in a standard place, and when one is not, it draws a pattern that can look like disease. Getting placement right is the cheapest way to make a 12-lead worth reading.

The limb electrodes

The four limb electrodes are right arm, left arm, right leg and left leg. The right leg electrode is a ground and does not form a lead of its own. Standard placement is on the limbs themselves, usually the wrists or forearms and the ankles or lower legs, on flat skin away from bone.

The common memory aids are "white on the right" and "smoke over fire" for black above red on the left side. Monitors built to the international IEC convention use a different set of colors, so read the letters on the lead wires if the colors are unfamiliar.

In the back of a moving ambulance many services place the limb electrodes on the shoulders and lower torso instead, because limbs move and produce artifact. That works, but it is not the same tracing: torso placement can shift the axis and change the size of complexes in the limb and inferior leads. Follow your monitor manufacturer and your service, and whichever placement you use, use the same one for every ECG on that patient so that a change between tracings is the patient and not the electrodes.

The six chest electrodes

Place V1 and V2 first, then V4, then V3 between them, then V5 and V6 out along the same horizontal line as V4. Placing V3 before V4 is how it ends up in the wrong place, because its position is defined by the two leads on either side.

Finding the fourth intercostal space

1. Find the sternal angle, the ridge where the handle of the sternum meets its body, a few finger-widths below the notch at the base of the neck.
2. The second rib joins the sternum at that ridge. Slide your finger just below the second rib: that is the second intercostal space.
3. Count down two more spaces along the edge of the sternum to reach the fourth intercostal space.
4. V1 sits there on the right of the sternum and V2 directly across on the left.

Counting from the sternal angle is more reliable than guessing from the nipple line, which varies widely between patients. The fifth intercostal space for V4 is one space lower, on the line straight down from the middle of the left clavicle.

Placing chest electrodes on a patient with breasts

V3 to V6 go on the chest wall beneath the breast rather than on top of breast tissue. Lift the breast, place the electrode on the chest wall at the correct landmark, and let the breast rest over it. Explain what you are doing and why before you do it, keep the patient covered as much as you can, and offer to let the patient lift the breast themselves.

Right-sided and posterior leads

Two extra views are used often enough in EMS to know where they go. Both are taken by moving chest electrodes you already have, which means the printout will still say V4, V5 or V6. Write the real lead names on the tracing before anybody else reads it.

What counts as a positive right-sided or posterior ECG, and what your system does with one, is interpretation rather than placement. The 12-lead interpretation basics guide covers what these views are looking for.

Placement errors that look like disease

• V1 and V2 too high, in the second or third intercostal space. This is the most common precordial error and it can produce a pattern that looks like septal or anterior change or a right bundle branch pattern.
• Left and right arm electrodes reversed. Lead I inverts, so the P wave, QRS and T wave in lead I all point down, and aVR can look upright. A tracing that suddenly shows right axis deviation, or a negative lead I with normal R-wave progression across V1 to V6, should prompt a check of the arm wires first.
• V4 to V6 drifting off a horizontal line, usually following the curve of the ribs upward. It distorts the progression across the lateral leads.
• Chest electrodes placed on breast tissue rather than the chest wall, which changes amplitude and moves the effective position.
• Poor skin contact. Hair, sweat, lotion and old electrodes all produce a noisy baseline. Clip hair if needed, dry the skin and use fresh electrodes.
• Movement and shivering. Ask the patient to rest their arms and stay still for the ten seconds the machine records, and keep the cables from pulling on the electrodes.

Serial ECGs

A second or third 12-lead is compared against the first, so it is only as useful as the placement is consistent. Leave the chest electrodes on between tracings when you can. If they have to come off, mark the positions with a skin marker so the next set goes back in the same place, and note on each printout the time it was taken.

Practicing it

Placement is a hands skill, and the landmarks feel different on every body. Practice counting intercostal spaces on classmates of different builds until you can find the fourth space without looking at the nipple line. Practice saying what you found as well: a handoff that includes the time of each 12-lead and what changed between them is more useful than one that only says a 12-lead was done.

Practice handing off your 12-lead findings in a structured report

The short version

• White on the right, smoke over fire, and read the letters if the colors are unfamiliar.
• Count down from the sternal angle to the fourth intercostal space for V1 and V2.
• Place V4 before V3, and keep V4, V5 and V6 on one horizontal line.
• V3 to V6 go on the chest wall under the breast, not on breast tissue.
• Relabel the printout whenever you take right-sided or posterior leads.
• Use the same placement for every ECG on the same patient.