How should I acutely treat and long‑term manage a patient with Wolff‑Parkinson‑White syndrome presenting with a regular narrow‑complex tachycardia?

Acute and Long-Term Management of WPW Syndrome with Regular Narrow-Complex Tachycardia

For a patient with Wolff-Parkinson-White syndrome presenting with regular narrow-complex tachycardia (orthodromic AVRT), initiate vagal maneuvers immediately, followed by intravenous adenosine if unsuccessful, and refer for catheter ablation as definitive first-line therapy. 1

Acute Management Algorithm for Narrow-Complex Tachycardia

First-Line Interventions

• Vagal maneuvers (Valsalva, carotid massage) should be attempted first as they are safe, effective, and immediately available (Class I recommendation). 1
• Intravenous adenosine (6 mg rapid IV push, followed by 12 mg if needed) is the pharmacologic agent of choice when vagal maneuvers fail, as it terminates orthodromic AVRT by blocking AV nodal conduction (Class I recommendation). 1, 2

Critical Safety Verification

• Always verify QRS width before administering adenosine or any AV-nodal blocker—these agents are safe only when the QRS is narrow (<120 ms), confirming anterograde conduction through the AV node rather than the accessory pathway. 2, 3
• If the QRS is wide (≥120 ms), adenosine and all AV-nodal blockers are absolutely contraindicated because they may precipitate ventricular fibrillation. 2, 3

Alternative Acute Pharmacologic Options

• Intravenous beta-blockers or calcium-channel blockers (diltiazem, verapamil) are effective for terminating orthodromic AVRT when the QRS is narrow (Class I recommendation). 1
• These agents work by blocking the anterograde limb of the reentry circuit at the AV node. 1

Emergency Cardioversion

• Synchronized electrical cardioversion is mandatory for hemodynamically unstable patients if vagal maneuvers and adenosine are ineffective or not feasible (Class I recommendation). 1
• Cardioversion is also indicated for hemodynamically stable patients when pharmacologic therapy fails or is contraindicated. 1

Long-Term Management: Definitive Therapy

Catheter Ablation as First-Line Treatment

• Radiofrequency catheter ablation of the accessory pathway is the definitive first-line treatment for all symptomatic WPW patients, with success rates exceeding 95% and major complication rates of only 0.1–0.9% (Class I recommendation). 2, 3
• Ablation eliminates the substrate for both orthodromic AVRT and the risk of life-threatening pre-excited atrial fibrillation. 2
• After successful ablation, no malignant arrhythmias or ventricular fibrillation occur during long-term follow-up (8-year observational data). 2

Indications for Ablation

• Mandatory indications include documented symptomatic tachyarrhythmias, history of syncope, documented atrial fibrillation with WPW, or shortest pre-excited R-R interval <250 ms during atrial fibrillation. 2, 3
• High-risk asymptomatic patients (young age, competitive athletes, family history of sudden cardiac death, multiple accessory pathways, posteroseptal pathway location) should undergo electrophysiologic study with possible ablation (Class IIa recommendation). 2

Pharmacologic Therapy When Ablation Is Declined or Not Feasible

For Prevention of Orthodromic AVRT

• Class IC agents (flecainide, propafenone) block accessory pathway conduction and prevent AVRT, with propafenone rendering AVRT non-inducible in approximately 69% of patients. 2
• AV-nodal blockers (beta-blockers, calcium-channel blockers) may be used for orthodromic AVRT prevention only if electrophysiologic study confirms the accessory pathway cannot conduct rapidly anterogradely—this is critical to avoid precipitating ventricular fibrillation during atrial fibrillation. 2

For Prevention of Pre-Excited Atrial Fibrillation

• Class IA agents (procainamide, quinidine, disopyramide) prolong accessory pathway refractory period (Class I recommendation). 2
• Class IC agents (flecainide, propafenone) are highly effective for slowing accessory pathway conduction (Class I recommendation). 2
• Class III agents (amiodarone, sotalol) can be employed in refractory cases (Class IIb recommendation). 2

Critical Pitfalls and Contraindications

Absolute Contraindications in Pre-Excited Atrial Fibrillation

• Never administer digoxin, diltiazem, verapamil, beta-blockers, or adenosine (when QRS ≥120 ms) during pre-excited atrial fibrillation, as these agents block the AV node while leaving the accessory pathway unopposed, leading to rapid ventricular rates and ventricular fibrillation (Class III recommendation). 1, 2, 3
• These medications shorten or do not affect the accessory pathway refractory period, allowing extremely rapid ventricular rates that can degenerate into ventricular fibrillation. 3

Common Diagnostic Pitfall

• Do not assume all narrow-complex tachycardias in WPW are safe for AV-nodal blockers—always verify the mechanism and QRS width before administering any rate-control medication. 3
• Atrial fibrillation can occasionally present with a narrow QRS if conduction is predominantly through the AV node, but this can change suddenly to pre-excited conduction. 4

Risk Stratification and Monitoring

High-Risk Features Requiring Urgent Intervention

• Shortest pre-excited R-R interval <250 ms during atrial fibrillation is the strongest predictor of sudden cardiac death risk and mandates ablation. 1, 2
• History of syncope suggests rapid accessory pathway conduction and high risk. 1, 2
• Multiple accessory pathways increase sudden death risk. 1, 2

Symptoms Requiring Immediate Evaluation

• Palpitations, syncope or near-syncope, dizziness during tachycardia, chest pain, shortness of breath, or fatigue during activities (especially driving) warrant urgent assessment. 2
• Sudden cardiac death risk in symptomatic WPW ranges from 0.15% to 0.39% over 3–10 years, with the highest risk in the first two decades of life. 1, 2

Special Populations

Pregnancy

• Acute management follows the same principles: immediate cardioversion if unstable, intravenous procainamide if stable with pre-excited atrial fibrillation. 2
• Catheter ablation can be considered in the second trimester when medically refractory (Class IIb recommendation). 2

Adolescents

• Adolescents are at particular risk for developing atrial fibrillation with WPW, which can degenerate into ventricular fibrillation. 3
• Catheter ablation is preferred to avoid lifelong antiarrhythmic therapy and has excellent outcomes in this age group. 3