Wolff-Parkinson-White Syndrome: Diagnostic Criteria and Management
Diagnostic Criteria
WPW syndrome is diagnosed by the presence of ventricular pre-excitation on ECG (delta wave, short PR interval, wide QRS complex) combined with documented symptomatic tachyarrhythmias. 1
Key ECG Features:
- Delta wave is the most critical diagnostic finding—it may be present even when PR interval is normal or QRS is narrow 2
- PR interval <120 ms (though may be normal in some cases) 2
- QRS duration >120 ms with slurred upstroke 2
- Secondary ST-T wave changes 1
- May mimic inferior myocardial infarction (pseudo-infarction pattern) 2
Risk Stratification for Sudden Cardiac Death:
Identify high-risk patients who require urgent intervention: 3
- History of symptomatic tachycardia (increases annual SCD risk to 2.2% vs 0.15-0.2% in asymptomatic patients) 3
- Short RR intervals (<250 ms) between pre-excited beats during atrial fibrillation 3
- History of syncope suggesting rapid heart rate 3
- Multiple accessory pathways 3
- Posteroseptal pathway location 3
Management Algorithm
Definitive Treatment: Catheter Ablation
Catheter ablation of the accessory pathway is the first-line definitive treatment for all symptomatic patients with WPW syndrome, particularly those with syncope, rapid heart rate, or short bypass tract refractory period. 4, 3
Ablation Outcomes:
- Success rate: >95% (up to 98.5%) 3
- Complication rate: <1-2% in experienced centers 3
- Permanent AV block risk: <1-2% 3
- Eliminates risk of sudden death from pre-excited AF 3
Important caveat: Ablation does not always prevent future atrial fibrillation, especially in older patients, and additional pharmacological therapy may be required. 4, 3
Acute Management of Arrhythmias in WPW
Step 1: Identify QRS Complex Width During Tachycardia
This determines whether the arrhythmia is life-threatening and dictates treatment:
Narrow QRS Complex (<120 ms) = Orthodromic AVRT (Safe)
Treatment sequence: 5
- Vagal maneuvers (Valsalva, carotid massage)—terminates 25% of cases 5
- Adenosine 6 mg IV push—terminates 95% of orthodromic AVRT 5
- AV nodal blockers (beta-blockers, calcium channel blockers, digoxin) are SAFE in this scenario 5
Wide QRS Complex (≥120 ms) = Pre-excited AF or Antidromic AVRT (DANGEROUS)
If hemodynamically unstable: Immediate direct-current cardioversion 4, 3, 5
If hemodynamically stable: 4, 5
CRITICAL: Absolutely Contraindicated Medications in Pre-excited AF
The following medications are Class III contraindications (DO NOT USE) in patients with WPW who have wide-complex tachycardia or pre-excited atrial fibrillation, as they can accelerate conduction through the accessory pathway and precipitate ventricular fibrillation: 4, 3, 5
- Adenosine (contraindicated in wide-complex WPW) 3, 5
- Digoxin 4, 3
- Beta-blockers (IV administration) 4, 3
- Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) 4, 3
- IV amiodarone 3, 5
Mechanism of harm: These agents increase AV nodal refractoriness, which encourages preferential conduction down the accessory pathway, potentially causing extremely rapid ventricular rates (>300 bpm) that degenerate into ventricular fibrillation. 4, 5
Long-term Pharmacological Management (When Ablation Not Performed)
For patients awaiting ablation or who decline/are not candidates for ablation, use medications that prolong accessory pathway refractoriness: 6
Preferred Agents:
Propafenone specifically: Reduces conduction and increases effective refractory period of the accessory pathway in both directions in WPW patients. 7
Agents for Orthodromic AVRT Prevention:
- Propranolol (drug of choice for regular SVT with narrow QRS) 2
- Digoxis (nearly equally effective for narrow-complex AVRT, but NEVER use in pre-excited AF) 2
Special Clinical Scenarios
Atrial Fibrillation in WPW:
- Occurs in approximately 25-50% of WPW patients 3, 8
- Can degenerate into ventricular fibrillation—this is the mechanism of sudden cardiac death in WPW 4, 3
- Immediate DC cardioversion if hemodynamically unstable 4
- IV procainamide or ibutilide if stable 4
Medications with QT-Prolonging Effects (e.g., Azithromycin):
Higher-risk WPW patients should avoid azithromycin: 9
- History of symptomatic tachycardia 9
- Short RR intervals (<250 ms) during pre-excited AF 9
- Multiple accessory pathways 9
Lower-risk patients (post-successful ablation) may use with caution and ECG monitoring. 9
Common Pitfalls to Avoid
Misdiagnosing pre-excited AF as ventricular tachycardia and administering AV nodal blockers—this can be fatal 8
Using adenosine in wide-complex tachycardia in WPW—adenosine is only safe when QRS is narrow (<120 ms), indicating orthodromic AVRT 4, 5
Delaying cardioversion in unstable pre-excited AF—immediate DC shock is life-saving 4
Assuming ablation prevents all future AF—continued monitoring is necessary, especially in older patients 4, 3
Missing the delta wave on ECG—it is the most important diagnostic feature and may be subtle 2