Management of Wolff-Parkinson-White Syndrome with Inverted P Wave
Catheter ablation of the accessory pathway is the definitive treatment of choice for patients with WPW syndrome presenting with inverted P waves, which likely indicates a posteroseptal accessory pathway with retrograde decremental conduction properties. 1, 2
Understanding Inverted P Waves in WPW
An inverted P wave in WPW syndrome typically suggests:
- Permanent junctional reciprocating tachycardia (PJRT), a unique form of orthodromic reentrant tachycardia
- A concealed accessory pathway, usually located in the posteroseptal region
- Retrograde decremental conduction properties
- Deeply inverted retrograde P waves in leads II, III, and aVF
- Long RP interval due to the location and conduction properties of the pathway
- Often an incessant nature that may result in tachycardia-induced cardiomyopathy 1
Acute Management
For Hemodynamically Unstable Patients:
- Immediate electrical cardioversion (Class I, Level of Evidence: B) for patients with severe hemodynamic compromise 1, 2
For Hemodynamically Stable Patients:
- Vagal maneuvers as first-line intervention (Class I, Level of Evidence: B-R) 1, 2
- Adenosine if vagal maneuvers fail and QRS is narrow (<120 ms) (Class I, Level of Evidence: B-R) 1, 2
- IV procainamide or ibutilide for patients with pre-excited AF (Class I, Level of Evidence: C) 1, 2
Medications to AVOID:
- AV nodal blocking agents including:
- Digoxin
- Diltiazem or verapamil
- Beta-blockers
These medications are contraindicated as they can increase the risk of ventricular fibrillation by preferentially blocking the AV node and allowing faster conduction through the accessory pathway 1, 2
Definitive Management
Catheter ablation of the accessory pathway is strongly recommended (Class I, Level of Evidence: B) for:
- Symptomatic patients with WPW syndrome
- Patients with syncope due to rapid heart rate
- Those with a short bypass tract refractory period
- Patients with documented pre-excited atrial fibrillation 1, 2
The success rate of catheter ablation for WPW syndrome is high (>95%), with low complication rates (2.5% overall) 3. However, patients with septal pathway locations (as suggested by inverted P waves) have higher complication rates (9.1% vs 2.0% for left pathways) 3.
Risk Stratification
Patients with WPW syndrome and inverted P waves should be assessed for risk factors for sudden cardiac death:
- Short refractory period of accessory pathway (<250 ms)
- Multiple accessory pathways
- History of pre-excited atrial fibrillation
- Shortest pre-excited R-R interval <250 ms during AF 1, 2
The risk of sudden cardiac death in WPW ranges from 0.15% to 0.6% per year, with the highest risk in the first two decades of life 1.
Special Considerations
For Asymptomatic Patients:
- Catheter ablation should be considered for:
For Patients Awaiting Definitive Treatment:
- Antiarrhythmic medications that prolong AP refractory periods (flecainide, propafenone, amiodarone) may be used temporarily 4
- However, prior use of antiarrhythmic medication is associated with higher recurrence rates after ablation (12.2% vs 7.6%) 3
Follow-up and Monitoring
- Regular cardiac monitoring and risk reassessment
- ECG evaluation at 3 months and annually during the first years
- Patient education about symptoms requiring immediate medical attention 2
Important Caveats
The incessant nature of PJRT (tachycardia with inverted P waves) may lead to tachycardia-induced cardiomyopathy that usually resolves after successful treatment 1
Electrophysiological study is essential for definitive diagnosis and treatment planning, especially when catheter ablation is considered 1
Patients with WPW and inverted P waves may have a unique form of accessory pathway that requires special consideration during ablation procedures 1