Pre-Excited AF (WPW): Do Not Block the Node
Objective: Recognize irregular wide-complex tachycardia as a possible WPW/AF emergency, withhold AV-nodal blockers, and cardiovert when perfusion is failing.
Why This Is Hard
It looks like AF with RVR, so crews reach for diltiazem or adenosine. If an accessory pathway is conducting, blocking the AV node funnels more impulses down the pathway and can precipitate VF. AHA 2025 ALS: treat irregular wide-complex tachycardia as dangerous — avoid AV-nodal blockers. Electricity is the clean street answer when they are unstable.
- Unstable (hypotension, shock, ischemic pain, AMS, acute heart failure): synchronized cardioversion per protocol — same as other unstable tachycardias.
- Do not give adenosine, diltiazem/verapamil, beta-blockers, or digoxin for irregular wide-complex tachycardia.
- Procainamide (or another protocol agent that acts on the pathway) is a hospital/ALS-protocol drug if they are stable. If you do not carry it, you still do not give diltiazem.
Street Sequence
- Pulse? If not, it is arrest — CPR and defibrillate polymorphic/VF as indicated.
- If there is a pulse: ABCs, 12-lead if it will not delay a crashing patient.
- Irregular + wide: treat as pre-excited AF until proven otherwise.
- Unstable → synchronized cardioversion. Stable → expert/protocol agent; do not block the node “to see.”
- After conversion, 12-lead. Delta waves may appear. Tell the ED what you did not give.
Field Rules (Education)
- The pattern: irregularly irregular, wide (or varying width) QRS, often very fast (sometimes >200).
- The trap: treating it like AF with RVR or like SVT. Adenosine and nondihydropyridine calcium-channel blockers are contraindicated in this picture.
- Unstable: electricity. AHA synchronized cardioversion energy per your protocol (same family as other unstable tachycardias).
- Narrow, regular SVT is a different lesson. This lesson is the irregular wide one.
- Irregular and wide — not giving adenosine or diltiazem
- Unstable: cardioversion
- If they arrest: treat as VF/pVT
- ED: possible pre-excited AF, no AV-nodal blocker given
Field Pitfalls
- Adenosine “just to see” on an irregular wide tachycardia.
- Diltiazem because the monitor said AF.
- Waiting for a perfect 12-lead while the BP is 70.
Practice
60-second drill
Monitor: irregular, wide, rate 220, BP 78/40, diaphoretic. Drug you will not give. Next action. Then: same tracing, BP 128, talking. What still stays in the box?
Related: Wide-Complex Tachycardia, Synchronized Cardioversion.
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 Part 9: Adult ALS — irregular wide-complex tachycardia — avoid AV-nodal blockers; cardiovert if unstable
- 2023 ACC/AHA/ACCP/HRS Atrial Fibrillation Guideline — pre-excited AF: cardioversion; AV-nodal blockers contraindicated
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.