Wolff Parkinson White Syndrome

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Epidemiology 5 Pathology 6 Diagnostic-procedures 7 Management 8 More General Terms 9 Additional Terms 10 Internet Database 11 References

More Specific Terms

• orthodromic AV reciprocating tachycardia

Introduction

• Orthodromic PSVT ( AV reciprocating tachycardia) with a normal QRS (no pre-excitation) is most common. Wide complex tachycardias in patients with WPW are generally orthodromic PSVT with rate-associated bundle-branch block. Less frequently, antidromic PSVT with a wide & bizarre QRS complex may occur resembling ventricular tachycardia.

Etiology

• accessory tract bypassing AV node, generally congenital
• generally no underlying heart disease
• clinical associations

• Ebstein's anomaly
• mitral valve prolapse
• cardiomyopathy

Epidemiology

• incidence of accessory pathway is 0.3% in the general population

Pathology

• pre-excitation & paroxysmal supraventricular tachycardia ( PSVT)
• an accessory bypass tract sets up a circuit which allows either:

• orthodromic conduction through the AV node with retrograde conduction through the accessory pathway ( orthodromic PSVT)*
• anterograde conduction through the accessory pathway with retrograde conduction through the AV node ( antidromic PSVT)*
• accessory path may be intermittantly anterograde or retrograde

• tachycardia develops in 70% of these patients
• increased tendency towards atrial fibrillation
• combined atrial fibrillation & ventricular pre-excitation (i.e. anterograde conduction through the accessory pathway) may predispose patients to ventricular fibrillation

• * Also orthodromic & antidromic reciprocating tachycardia.

Diagnostic-procedures

• electrocardiogram:

• ventricular pre-excitation ( delta wave)*

• due to anterograde conduction through the accessory pathway
• patients with accessory pathways that conduct only in the retrograde direction do NOT have a pre-excitation delta wave
• pre-excitation may be enhanced by slowing conduction through the AV node

• carotid sinus massage
• vagal maneuvers
• short-acting AV nodal blocking agents

• short PR interval (< 120 msec)*
• wide QRS complex (> 120 msec)*
• paroxysmal supraventricular tachycardia ( PSVT)*
• may be Q-wave in V1- V3
• may be R in V1
• ST & T wave changes opposite in polarity to QRS complex
• wide complex tachycardias

• orthodromic tachycardia with bundle-branch block
• antidromic tachycardia

• inverted p-wave prior to every QRS
• short, but constant PR interval
• no isoelectric PR segment
• wide & bizarre QRS morphology

• atrial fibrillation

• irregular baseline & rhythm
• no p-waves
• QRS variable from normal to wide, bizarre (pre-excited) complexes
• rate may be rapid

• atrial flutter

• narrow complex tachycardia (most common)

• orthodromic conduction in the absence of bundle-branch block

• atrial fibrillation can convert to ventricular fibrillation

• electrophysiology

• asymptomatic patients with WPW in sinus rhythm do not require electrophysiology studies

• * defining criteria for WPW

Management

• acute episodes are managed similar to AVNRT

• vagal maneuvers

• carotid massage
• Valsalva maneuver

• AV nodal blocking agents (short-acting) *see below*

• adenosine 6-12 mg IV
• verapamil 5 mg IV every 5 min for a maximum of 3 doses
• diltiazem 15-20 mg IV over 2 min for a maximum of 2 doses

• adenosine may potentiate short periods of atrial fibrillation - DC cardioversion should be available
• cardioversion for any unstable patient

• wide complex tachycardia

• lidocaine may precipitate ventricular tachycardia
• synchronized cardioversion
• procainamide may be used

• atrial fibrillation

• AV blocking agents contraindicated

• Ca+2-channel antagonists, beta-blockers, digoxin
• will NOT prevent & may precipitate a rapid ventricular response to atrial fibrillation if anterograde conduction occurs through the accessory pathway.

• use class Ia, Ic & III anti-arrhythmic agents [4]

• class Ia anti-arrhythmic agents

• quinidine, procainamide

• intravenous procainamide (drug of choice) - up to 15 mg/kg IV at 25-50 mg/min - monitor BP every 5 min

• class Ic anti-arrhythmic agents

• flecainide, propafenone

• class III anti-arrhythmic agents

• amiodarone, ibutilide

• cardioversion if hemodynamic compromise

• chronic therapy

• class Ia, Ic & III anti-arrhythmic agents

• slows conduction in accessory pathway
• procainamide (preferred agent in pregnancy)
• flecainide

• if NO atrial fibrillation

• beta-blocker
• calcium channel antagonist

• electrophysiologic testing

• symptomatic patients
• asymptomatic patients in high-risk occupations

• pilots
• bus drivers

• radio frequency catheter ablation of accessory tract

• curative
• indications

• drug resistant tachycardia
• patients who do not wish to take long-term drugs
• 1st line therapy [4]

• contraindications:

• avoid during pregnancy, radiation exposure of fluoroscopy

More General Terms

• narrow complex tachycardia
• re-entry
• chronic cardiac arrhythmia

Additional Terms

• antiarrhythmic agent, Group IA
• antiarrhythmic agent, Group IC
• antiarrhythmic agent, Group III
• atrial fibrillation (AF)
• AV nodal re-entrant tachycardia (AVNRT)
• Ebstein's anomaly
• paroxysmal supraventricular tachycardia (PSVT)
• pre-excitation
• ventricular fibrillation (V Fib)

Internet Database

OMIM: 194200
OMIM: 600858

References

1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 145
2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 274
3. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 77-79
4. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15 American College of Physicians, Philadelphia 1998, 2006, 2009
5. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1032

Wolff-Parkinson-White (WPW) syndrome