What is the recommended diagnostic work‑up and acute and long‑term management for a patient with Wolff‑Parkinson‑White (WPW) syndrome presenting with documented symptomatic supraventricular tachycardia or atrial fibrillation?

Management of Wolff-Parkinson-White Syndrome with Documented Symptomatic Arrhythmias

Catheter ablation is the definitive first-line treatment for all patients with WPW syndrome presenting with documented symptomatic supraventricular tachycardia or atrial fibrillation, with success rates exceeding 95% and major complication rates of only 0.1–0.9%. 1, 2

Diagnostic Work-Up

Initial ECG Confirmation

• Verify the presence of delta waves (slurred upstroke of the QRS complex), PR interval <120 ms, and QRS duration >120 ms to confirm ventricular pre-excitation. 1, 3
• Obtain a 12-lead ECG during tachycardia episodes whenever possible to document the arrhythmia mechanism (orthodromic AVRT versus pre-excited AF). 1

Risk Stratification Studies

• Electrophysiological study is the gold standard for risk assessment and should be performed in all symptomatic patients to measure the shortest pre-excited R-R interval during induced AF, accessory pathway effective refractory period, and identify multiple pathways. 1, 2
• 24-hour Holter monitoring detects paroxysmal arrhythmias and assesses for intermittent pre-excitation (which predicts low risk with 90% positive predictive value). 1
• Exercise ECG testing evaluates whether pre-excitation disappears abruptly with exercise, suggesting a long anterograde refractory period and lower sudden death risk. 1

Structural Heart Disease Evaluation

• Echocardiography is mandatory to exclude Ebstein's anomaly, hypertrophic cardiomyopathy, and PRKAG2-related familial WPW (glycogen storage cardiomyopathy). 1
• Obtain detailed family history focusing on pre-excitation in first-degree relatives, sudden cardiac death in young family members, and cardiomyopathy. 1

High-Risk Features Requiring Urgent Intervention

• Shortest pre-excited R-R interval <250 ms during atrial fibrillation (strongest predictor of life-threatening events). 1, 2
• Accessory pathway effective refractory period <240 ms. 1
• History of syncope or presyncope during tachyarrhythmias. 1, 2
• Multiple accessory pathways or posteroseptal pathway location. 1, 2
• Inducible sustained AVRT that degenerates into pre-excited AF during EP study. 1

Acute Management

Pre-Excited Atrial Fibrillation (Wide QRS ≥120 ms)

Hemodynamically Unstable

• Immediate synchronized electrical cardioversion is the priority intervention (Class I recommendation) to prevent progression to ventricular fibrillation. 1, 2, 4

Hemodynamically Stable

• Intravenous procainamide is the first-line drug (Class I) to block accessory pathway conduction and slow ventricular rate. 1, 2, 4
• Intravenous ibutilide is an equally effective alternative (Class I). 1, 4
• Class IC agents (flecainide, propafenone) are highly effective for slowing accessory pathway conduction (Class I). 1, 4

Absolutely Contraindicated Medications

• Never administer AV-nodal blocking agents in pre-excited AF: digoxin, diltiazem, verapamil, beta-blockers (metoprolol, esmolol, propranolol), or adenosine when QRS is wide (≥120 ms). 1, 2, 4
• These agents block the AV node while leaving the accessory pathway unopposed, paradoxically accelerating ventricular rates and precipitating ventricular fibrillation. 1, 4

Orthodromic AVRT (Narrow QRS <120 ms)

• Vagal maneuvers should be attempted first (Class I). 1
• Intravenous adenosine is safe and effective for terminating orthodromic AVRT when the QRS is narrow (Class I). 1
• AV-nodal blocking agents (beta-blockers, calcium-channel blockers) are effective in this narrow-complex setting (Class I). 1
• Critical caveat: Always verify QRS width before administering adenosine or AV-nodal blockers; they are contraindicated if QRS ≥120 ms. 1, 4

Long-Term Management

Definitive Treatment: Catheter Ablation

• Catheter ablation is mandatory (Class I recommendation) for all symptomatic patients with documented arrhythmias, particularly those with syncope, documented AF, or shortest pre-excited R-R interval <250 ms. 1, 2, 4
• Success rates are 95–98.5% with final success after repeat procedures if needed. 1, 4
• Major complication rates are 0.1–0.9%, including complete heart block (0.1%), right bundle-branch block (0.9%), and left bundle-branch block (0.3%). 1, 4
• No patients developed malignant arrhythmias or ventricular fibrillation over 8 years of follow-up after successful ablation. 5, 4
• Ablation should be performed in experienced centers to minimize complications. 2, 4

Pharmacologic Therapy (When Ablation Declined or Not Feasible)

For Prevention of Pre-Excited AF

• Class IA agents (procainamide, quinidine, disopyramide) prolong accessory pathway refractory period (Class I). 1
• Class IC agents (flecainide, propafenone) are highly effective for blocking accessory pathway conduction (Class I). 1
• Class III agents (amiodarone, sotalol) can be employed in refractory cases (Class IIb). 1

For Prevention of Orthodromic AVRT

• Class IC agents block accessory pathway conduction; propafenone rendered AVRT non-inducible in 69% of patients. 1
• AV-nodal blockers may be used only if EP study confirms the accessory pathway cannot conduct rapidly anterogradely. 1

Post-Ablation Monitoring

• Ablation of the accessory pathway does not always prevent atrial fibrillation, especially in older patients; additional therapy may be required. 4
• Monitor for arrhythmia recurrence, though rates are low (7% at 5 years in ablated patients versus 77% in non-ablated patients). 1
• No specific bradycardia monitoring is needed unless AV-node ablation was performed (which requires permanent pacemaker implantation). 1

Special Populations

Pregnancy

• Acute management follows the same principles: immediate cardioversion if unstable, intravenous procainamide if stable. 1
• Catheter ablation can be considered in the second trimester when medically refractory (Class IIb). 1

Asymptomatic Patients with High-Risk Features

• EP study with possible ablation is reasonable (Class IIa) for young patients, competitive athletes, those with family history of sudden cardiac death, multiple accessory pathways, or posteroseptal pathway location. 1, 2

Common Pitfalls to Avoid

• Do not assume narrow-complex tachycardia is safe for AV-nodal blockers; always verify the underlying mechanism before administering rate-control medication. 4
• Standard atrial fibrillation rate-control protocols that include digoxin, beta-blockers, or calcium-channel blockers should be avoided in patients with known or suspected WPW. 4
• Misdiagnosing pre-excited AF as ventricular tachycardia can lead to inappropriate treatment; look for irregular R-R intervals and varying QRS morphology in pre-excited AF. 6
• Bradycardia in WPW patients is typically iatrogenic from inappropriate AV-nodal blocking agents, not from the accessory pathway itself; discontinue these medications immediately. 1