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Lesson

Defibrillation Pads & Vector Change

11 min Cardiac & ECG Skip to quiz

Objective: Place adult pads anterolateral with a real cardiac vector, avoid breast tissue, and treat pad position as part of refractory VF — not an afterthought.

Why This Is Hard

Pads get slapped on the pecs an inch apart, or parked on breast tissue, and then the crew blames the joules. AHA 2025: optimized pad placement matters for shock success. Anterolateral remains the fast first position during CPR. Vector change to anterior-posterior after several failed shocks is a 2b / “usefulness not established” move in ALS — DSED is a separate lesson. Do not steal compression time to make it pretty on shock one.

On this truck
  • Right pad: below the right clavicle, right of the sternum. Left pad: left mid-axillary, inferior to the axilla, not on the nipple or breast mound.
  • For women: move breast tissue, do not park the pad on it. AHA 2025 notes public-access defibrillation gaps in women — do not be part of that gap.
  • Refractory VF after several shocks: if protocol includes vector change, new pads anterior-posterior (anterior left precordium, posterior left of the spine below the scapula) without turning CPR into a photo shoot.

Street Sequence

  1. Pads on during the first compression pause plan. Anterolateral. Charge. Shock. CPR immediately.
  2. If VF persists: high-quality CPR, antiarrhythmic per protocol, check pad contact and position before you blame the machine.
  3. After ≥3 failed shocks, if your medical direction includes vector change: AP pads, then shock. DSED is only if you are trained and authorized — see that lesson.
  4. Peds: use the right pad size. AP is often the fit when pads would overlap on a small chest.

Field Rules (Education)

  • Vector = through the heart. Pads on the same side of the chest are decoration.
  • Anterolateral first: fastest during CPR. Do not delay the first shock to roll for AP.
  • Vector change (AP after failed AL shocks) is a considered option in 2025 ALS — usefulness not firmly established. Protocol owns it. It is not a substitute for CPR quality.
  • DSED ≠ vector change. Double sequential uses two defibrillators. Do not improvise a second monitor you are not trained to fire.
Say out loud
  • Pads anterolateral — clear of breast tissue
  • Vector through the heart
  • VF still there: check pads before the next excuse
  • AP vector change only if protocol after failed shocks

Field Pitfalls

  • Both pads on the anterior chest an inch apart.
  • Leaving a pad on breast tissue because you were shy.
  • Stopping two minutes of CPR to “try AP” before the first shock.

Practice

60-second drill

VF, pads already on the upper pecs almost touching. What do you fix before the next shock? Then: three failed AL shocks, 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

Street decisions from this lesson only. 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 on breast tissue:
3. Vector change to anterior-posterior is best framed as:
4. DSED compared with vector change:
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