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Lesson

Defibrillation Pads & Vector Change

11 min Cardiac & ECG Skip to quiz

Objective: Place the pads so the shock goes through the heart. Use anterolateral first. Move the pads only if protocol allows it after failed shocks. Vector change is not routine.

Why this matters

Pads placed an inch apart on the upper chest do not send the shock through the heart. Pads left on breast tissue miss it too. Check pad position before you blame the energy setting.

Anterolateral is the fast first position during CPR. Do not stop compressions to perfect the pads before the first shock. Vector change means moving to anterior-posterior pads after several failed shocks. AHA 2025 says usefulness has not been established. That is Class 2b. It is not routine, and it is not the first shock. Use it only if protocol includes it. Double sequential defibrillation uses two defibrillators. That is a separate lesson.

Key points
  • Place the right pad below the right clavicle, to the right of the sternum. Place the left pad on the left mid-axillary line, below the axilla, not on the nipple or the breast.
  • Move breast tissue out of the way. Do not leave the pad on it. Place the pad on the chest wall.
  • If VF persists after several shocks and protocol includes vector change, place new pads anterior-posterior. VF means ventricular fibrillation. Put one pad on the front of the left chest and one on the back, just left of the spine and below the scapula. Do not stop CPR for a long pad rearrangement.
Anterolateral defibrillator pads. One pad is on the right upper chest and the other is on the left side of the chest.
The picture is the anterolateral pair, which is the first position. The right pad goes below the right clavicle, to the right of the sternum. The left pad goes on the left mid-axillary line, below the armpit, on the chest wall. Move breast tissue out of the way. Anterior-posterior pads, one on the front of the left chest and one on the back just left of the spine below the scapula, are a different position. Use that position only after failed shocks, and only if protocol includes vector change. They are not in this picture. AHA 2025 says usefulness has not been established. That position is not the first shock and it is not routine. Use it only if protocol includes it. On a small chest, anterior-posterior placement is used when the two pads would overlap. That is a size problem, separate from vector change. Pad positions by Owain Davies, Wikimedia Commons, CC BY 3.0. Cropped and contrast adjusted.

Clinical sequence

  1. Put the pads on during the first planned pause. Use anterolateral. Charge, shock, and put hands back on the chest at once.
  2. If VF persists, keep high-quality CPR. Give an antiarrhythmic per protocol. Check pad contact and position before you blame the defibrillator.
  3. After three or more failed shocks, move to anterior-posterior pads only if medical direction includes vector change, then shock. Double sequential defibrillation is only if you are trained and authorized. See that lesson. It is not routine.
  4. In children, use the correct pad size. Use anterior-posterior when the pads would overlap on a small chest.

Teaching points

  • The shock has to cross the heart. Pads on the same side of the chest do not do that.
  • Anterolateral first. It is the fastest position during CPR. Do not delay the first shock to roll the patient for anterior-posterior pads.
  • Vector change means anterior-posterior pads after failed anterolateral shocks. AHA 2025 Class 2b: usefulness has not been established. It is not routine and it is not the first shock. Use it only if protocol includes it. It does not replace high-quality CPR.
  • Double sequential defibrillation is not a pad move. It uses two defibrillators. Do not improvise a second monitor you are not trained to use.
Verbalize
  • Pads are anterolateral and clear of breast tissue.
  • The shock goes through the heart.
  • If VF is still there, check the pads before the next shock.
  • Use anterior-posterior vector change only if protocol allows it after failed shocks.

Common errors

  • Putting both pads on the front of the chest an inch apart.
  • Leaving a pad on breast tissue.
  • Stopping CPR for a long time to try anterior-posterior pads before the first shock.

Practice

One-minute check

VF, and the pads are already on the upper chest almost touching. What do you fix before the next shock? Then: three anterolateral shocks have failed, and protocol allows vector change. Where do the new pads go?

Related: Shockable Arrest: VF & pVT, Double Sequential Defibrillation Framing.

Sources & Further Study

Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.

Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.

Check Your Understanding

Questions drawn only from this lesson. After you check, the key is highlighted. Education practice — not a certification exam.

1. The first-line adult pad position during CPR is:
2. Pads parked on breast tissue:
3. Vector change to anterior-posterior is best treated as:
4. Double sequential defibrillation (DSED), compared with vector change:
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