Cardiovascular · Topic 18 of 48

Wolff-Parkinson-White & Pre-excitation

Cardiovascular · accessory pathway

Wolff-Parkinson-White & Pre-excitation

An accessory pathway bypasses the AV node. Pre-excited AF can become VF: no AV-nodal blockers — cardiovert, or give procainamide or ibutilide.

Key numbers

Short PR, delta wave, wide QRSPR < 120 ms

Pre-excited AF: fast, irregular, wide, bizarreup to 200–300 bpm

Refer for accessory-pathway catheter ablation≈ 94% success

High-risk pathway: shortest pre-excited RR ≤ 250 msSPERRI ≤ 250 ms

01 · Defined byShort PR, delta wave, wide QRS

Pre-excitation on a sinus-rhythm ECG: short PR interval (< 120 ms), a slurred initial QRS upstroke (delta wave) and a wide QRS (≥ 120 ms), with secondary ST–T changes.

02 · AvoidNo nodal blockers in pre-excited AF

In pre-excited AF, adenosine, verapamil, diltiazem, digoxin, beta-blockers and amiodarone are contraindicated (Class 3: Harm) — blocking the AV node speeds pathway conduction and can precipitate VF.

03 · DoCardiovert if unstable; else procainamide/ibutilide

Pre-excited AF with hemodynamic instability → synchronized electrical cardioversion; if stable, give IV procainamide or IV ibutilide (or elective cardioversion) to slow accessory-pathway conduction.

What it is

Core idea

WPW syndrome: pre-excitation plus tachyarrhythmiaWPW syndrome is ventricular pre-excitation over an accessory AV pathway together with symptomatic tachyarrhythmia; the ECG pattern without symptoms is called the WPW pattern.

Causes & risk factors

Why it happens

High-risk pathway: shortest pre-excited RR ≤ 250 msAbrupt loss of pre-excitation during exercise suggests a low-risk pathway; a shortest pre-excited RR interval or pathway refractory period ≤ 250 ms at EP study marks a high-risk pathway.

Sudden death can be the first signSudden death is uncommon (about 0.1% per year) but may be the first manifestation, especially in adolescents; risk rises with young age, exercise, multiple pathways and digoxin.

Presentation

What you'll see

Pre-excited AF: fast, irregular, wide, bizarre must knowPre-excited AF is a very fast (up to 200–300 bpm), irregular, mostly wide-QRS rhythm whose QRS shape varies; the AV node is bypassed and the rhythm can degenerate into VF.

Do right now

In this order

First moves

Pre-excited AF: fast, irregular, wide, bizarreup to 200–300 bpm

→

No nodal blockers in pre-excited AF

→

Cardiovert if unstable; else procainamide/ibutilide

Why each step

Pre-excited AF: fast, irregular, wide, bizarrePre-excited AF is a very fast (up to 200–300 bpm), irregular, mostly wide-QRS rhythm whose QRS shape varies; the AV node is bypassed and the rhythm can degenerate into VF.

No nodal blockers in pre-excited AFIn pre-excited AF, adenosine, verapamil, diltiazem, digoxin, beta-blockers and amiodarone are contraindicated (Class 3: Harm) — blocking the AV node speeds pathway conduction and can precipitate VF.

Cardiovert if unstable; else procainamide/ibutilidePre-excited AF with hemodynamic instability → synchronized electrical cardioversion; if stable, give IV procainamide or IV ibutilide (or elective cardioversion) to slow accessory-pathway conduction.

Management

Orders

Narrow regular WPW tachycardia: treat like SVTA regular narrow-complex tachycardia (120–250 bpm) in WPW is almost always orthodromic AVRT (down the AV node, up the pathway): vagal maneuvers, then IV adenosine; cardiovert if unstable.

Regular wide WPW tachycardia: procainamide or cardioversionA regular wide-complex tachycardia in WPW (antidromic AVRT, pathway-conducted SVT or VT): synchronized cardioversion if unstable; if stable, IV procainamide, IV amiodarone or cardioversion.

Refer for accessory-pathway catheter ablationCatheter ablation of the accessory pathway is the long-term treatment for any WPW-related tachyarrhythmia and is recommended for pre-excited AF: about 94% success, 6% recurrence, 1% complications.

No ablation: flecainide or propafenone, never digoxinIf ablation is declined or impossible, oral flecainide or propafenone (no structural heart disease) is preferred; avoid digoxin, and do not use a beta-blocker or nondihydropyridine CCB alone.

The rules

Know these

Known WPW: IV beta-blocker/CCB only cautiouslyIn known WPW, IV beta-blockers, diltiazem or verapamil after adenosine failure carry only a Class IIb recommendation, because AVRT can convert to pre-excited AF with a faster ventricular rate.

Orthodromic AVRT or pre-excited AF?

Commonly confused

Rhythm	Regular
QRS	Narrow (unless bundle branch block)
Rate	120–250 bpm
Adenosine and AV-nodal blockers	Adenosine after vagal maneuvers
Stable patient	Vagal maneuvers, then adenosine

Commonly confused

Tell apart

Concealed pathway: normal ECG, no AF dangerA concealed accessory pathway conducts only retrograde: the sinus ECG is normal and orthodromic AVRT can occur, but there is no risk of rapidly conducted pre-excited AF.

More detail

Reference

Show 6 reference facts

WPW is mostly idiopathic but is more common with hypertrophic cardiomyopathy, transposition of the great vessels and Ebstein anomaly.

Manifest WPW affects about 1–3 per 1000 people; the estimated risk of developing AF is about 1.5% per year.

Depending on delta-wave direction, pre-excitation can produce pseudo-infarction Q waves and abnormal T waves on the resting ECG.

Orthodromic AVRT is about 95% of AVRT; antidromic AVRT runs down the pathway (fully pre-excited, wide QRS), and about 5% of patients have more than one accessory pathway.

The accessory pathway behaves like atrial muscle — its refractory period shortens at fast rates — so unlike the AV node it does not limit the ventricular response to AF.

A clue to pre-excited AF is a very rapid, mostly wide-QRS irregular rhythm with occasional narrow beats that do not follow a long RR interval; QRS shapes are fusions of wide and narrow.

Pearl

In WPW with AF, block the pathway, not the node: procainamide or ibutilide — or shock.

Sources · Exercise stress test for detecting high-risk accessory pathways in Wolff-Parkinson-White syndrome (editorial). Arq Bras Cardiol 2025 — PMC · Merck Manual Professional — Wolff-Parkinson-White Syndrome (WPW Syndrome) · Merck Manual Professional — Atrial Fibrillation and Wolff-Parkinson-White Syndrome · Joglar JA et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation. Circulation 2024;149:e1–e156 — PMC · Merck Manual Professional — Reentrant (Paroxysmal) Supraventricular Tachycardias (PSVT) · 2025 AHA Guidelines for CPR and ECC — Part 9: Adult Advanced Life Support (Circulation 2025; doi 10.1161/CIR.0000000000001376), cpr.heart.org text · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).