In adult cardiac arrest, pad placement matters.
But not because one position is clearly superior.
It matters because good placement helps the shock reach the heart.
That is the goal.
You need enough current to pass through the myocardium and terminate ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT).
First principle: do not overcomplicate pad placement
What does the evidence actually show?
The data do not show a clear winner between pad positions.
For adult cardiac arrest, anterolateral (AL) and anteroposterior (AP) placement are both reasonable.
ERC 2025 favors AL initially because it is quick to apply with less patient handling. Follow your device’s placement instructions. ERC guidance.
A before-and-after study found similar VF/VT termination with AP and sternal-apical (AL) placement. Steinberg et al., 2022.
A separate observational cohort associated AP placement with more return of spontaneous circulation (ROSC), without a statistically significant difference in discharge survival or neurological outcome. These comparisons do not establish causal superiority. Lupton et al., 2024.
Persisting VF/pVT after three shocks is a separate problem. Check position, adhesion and energy first. AHA considers the usefulness of vector change and double sequential defibrillation unestablished. AHA ALS.
ERC permits consideration of AL-to-AP vector change, but does not recommend routine double sequential external defibrillation (DSED) with two defibrillators. Follow your local ALS protocol. ERC ALS.
DOSE-VF reported higher discharge survival with vector change and DSED but stopped early. The 2026 DoubleD pilot addressed feasibility, not definitive survival benefit. Neither establishes AP as the best initial pad position. DOSE-VF; DoubleD.
Adult defibrillator pad placement checklist
Place pads on the bare chest.
Use compatible adult pads without delaying defibrillation to measure them. AHA considers an electrode diameter above 8 cm reasonable; ERC does not specify an optimal size. AHA; ERC.
Children need a pediatric approach. Under 8 years, use AED pediatric attenuation when available; an unattenuated AED can be used if neither attenuation nor a manual defibrillator is available. Use pads that fit with good separation; AP placement is an option. Follow the pediatric protocol and device diagram. AHA pediatric BLS.
Press the pads into full skin contact before shock delivery. Dry wet skin. Remove hair only where it prevents adhesion, without delaying a shock. RCUK; ERC.
Do not place a pad over a medication patch. Remove the patch and wipe the skin, or use an appropriate alternative pad position if removal would delay defibrillation. RCUK preparation guidance.
Do not let pads touch each other.
For AL placement, put the right pad below the right clavicle beside the upper sternum. Center the left pad on the mid-axillary line below the armpit, clear of breast tissue. ERC pad-position guidance.
Not too anterior.
That small mistake can change the shock vector.
And that can reduce effectiveness.
For AP placement, follow the pad diagram: the anterior pad is over the left precordium, avoiding breast tissue; the posterior pad lies left of the spine, just below the scapula. ERC guidance.
Avoid implanted pacemakers or defibrillators: ERC advises placing pads more than 8 cm away or choosing another position. ERC guidance.
The physiology is simple
A shock works by depolarizing a critical mass of heart muscle.
Poor skin contact can increase transthoracic impedance. Pad location also changes the shock vector: misplaced pads may direct less current through the myocardium. Both contact and anatomical position matter.
CPR still comes first
Do not pause and stare at the monitor.
Do not stop compressions early.
For adults in cardiac arrest, perform CPR until the defibrillator or AED is applied.
If the arrest is unmonitored, a brief period of CPR while the defibrillator is being prepared is reasonable.
If VF/pVT is witnessed or monitored, and the defibrillator is already there, shock immediately.
Clear contact for AED analysis and every shock; ordinary gloves do not make hands-on shocks safe. Move free-flowing oxygen at least 1 m from the chest. Keep a bag or circuit attached to an advanced airway, directing exhaust away. Resume CPR immediately. ERC; RCUK.
A useful 2025 update
A bra does not always need to be removed.
Adjust it if pads can sit correctly on bare skin. Remove it if it obstructs placement or contact; do not let concerns about exposure delay treatment. RCUK 2025.
This is practical.
It may also reduce hesitation in public defibrillation.
What should the team remember?
Do not chase perfection.
Chase effective defibrillation.
That means:
- bare chest
- good pad contact
- correct position
- minimal pause in CPR
- fast shock delivery when appropriate
The bedside takeaway
In adult cardiac arrest, the winning strategy is not fancy.
It is disciplined basics.
Place the pads well.
Keep the lateral AL pad in the mid-axilla.
Continue CPR until the device is ready.
Shock early when VF/pVT is witnessed and the defibrillator is immediately available.
Then get right back on the chest.
Effective defibrillation depends on good contact, correct placement and the shortest safe interruption in CPR.
Sources and related learning
The pad-position and timing recommendations above follow the 2025 AHA adult BLS guideline, sections 9.1–9.2. Shock-vector and impedance considerations are discussed in the AHA adult ALS guideline.
