Shockable Arrest: VF & pVT

Why this matters

When you see ventricular fibrillation (VF) or pulseless ventricular tachycardia, shock it and put hands back on the chest. The steps look simple on a poster. They are harder on a real arrest. People stop compressions to stare, to argue about the pads, or to “charge while we check,” sometimes for 20 seconds. Blood flow through the heart muscle falls every time the chest is empty. Check the gain and the pads before you call a flat line asystole. Fine VF is still shockable. See that lesson. Do not hunt for a pulse after the shock. Check the rhythm on the next planned pause.

Clinical sequence

1. Name it. VF and pulseless ventricular tachycardia (pVT) are shockable.
2. Clear the patient, deliver the shock, then start CPR immediately. Do not search for a pulse after the shock until the next planned rhythm check.
3. Do the next rhythm check on the planned cycle. Do not check after every shock.
4. Use double sequential defibrillation (DSED — two defibrillators) or vector change (a pad move) only if protocol includes it after several failed shocks. AHA 2025 says usefulness has not been established (Class 2b). It is not routine. It is not the first shock.

The Cycle

1. Confirm arrest. Do high-quality CPR while the defibrillator charges if your system allows that.
2. Clear, shock VF or pVT at the protocol energy, and start CPR again at once. Do not check a pulse after the shock until the next planned rhythm check.
3. Keep the pause around the shock short. Charge during compressions if you are trained and the device allows it.
4. Follow your arrest protocol for the airway and for epinephrine timing. Those steps do not come ahead of defibrillation and CPR quality in a shockable arrest.
5. If the screen looks flat, check the gain, the pads, and a second view. Fine VF is still shockable.

Do not improvise these

• After three or more shocks in a row, the usefulness of vector change and double sequential defibrillation has not been established (AHA 2025 Class 2b). It is not recommended as routine care. It is not the first shock. Use it only if your protocol and medical direction include it for VF or pVT that will not clear.
• Do not stack shocks without CPR unless your current protocol still says to. Current teaching is shock, then start CPR again at once.
• Do not shock asystole “just in case.”

Common errors

• The crew pauses a long time to ask whether the VF is coarse enough.
• Someone checks a pulse after every shock instead of after a full CPR interval.
• The chest is left wet or hairy, so the pads do not deliver energy into the heart.

Practice

Related: Asystole vs Fine VF, ROSC & Post-Arrest Care.

Sources & Further Study

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

• NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; protocol still wins
• AHA 2025 Adult Advanced Life Support (CPR & ECC Part 9)
• VF and pulseless VT are shockable. Immediate CPR after the shock, short peri-shock pauses, high-quality compressions. DSED/vector-change usefulness has not been established (Class 2b after ≥3 shocks) — not routine; protocol only.