Arrhythmias, Wolff-Parkinson-White Syndrome

Basics

Description

Wolff-Parkinson-White (WPW) syndrome is defined by the combination of preexcitation on the EKG (δ wave) and supraventricular tachycardia (either atrial fibrillation or reentrant tachycardia using the accessory pathway as part of the circuit). In the purest sense, simple preexcitation without arrhythmias is not the "syndrome."�
Synonym(s): Paroxysmal atrial tachycardia (PAT): Term now obsolete.

Pregnancy is not contraindicated, but supraventricular tachycardias may be more frequent and precipitated by pregnancy. �

Epidemiology

Supraventricular tachycardia and WPW syndrome can occur at any age. Conversely, accessory pathway conduction may disappear with aging.
The prevalence of EKG preexcitation has been reported to range from 0.1-3/1,000 population.
The intermittent nature of preexcitation may have led to underestimation of the true prevalence of the disease.
Accessory pathway-mediated tachycardia accounts for about 30-40% of paroxysmal supraventricular tachycardias seen in practice.
WPW syndrome is more frequent in males.

Etiology

WPW syndrome results from a developmental abnormality of the atrioventricular (AV) groove.
During normal cardiogenesis, direct continuity between the atrial and ventricular myocardium is lost by growth of the annulus fibrosis.
Defects in the annulus leave muscular connection(s) called accessory pathways or Kent bundles between the atrial and ventricular myocardium.
By bypassing the AV node, these pathways can lead to preexcitation of the ventricles because atrial impulses are not delayed in the AV node.
Accessory pathways are most often described in electrical terms, with the EKG showing the characteristic δ wave, or they are identified at the electrophysiologic study. The pathways typically have "all or none"� conduction properties, or rarely have decremental conduction properties, as does the AV node. They may conduct only from the atria to the ventricles (called anterograde or antegrade conduction), only from the ventricles to the atria (called retrograde conduction), or in both directions.
The majority of patients with WPW syndrome do not have a familial/genetic disorder. However, there have been case reports of autosomal-dominant inheritance without associated cardiac disorders.
Right-sided accessory pathways may be associated with Ebstein anomaly of the tricuspid valve.
Other conditions that have been associated with WPW syndrome are hypertrophic cardiomyopathy, mitral valve prolapse, and a variety of congenital heart diseases.

Diagnosis

Signs and symptoms: �

Palpitations
Dyspnea
Dizziness
Syncope
Fatigue (sometimes related to drug therapy)
Chest pain
Diaphoresis
Polyuria (usually following tachycardia)

Tests

EKG is the cornerstone of diagnosis: �

The EKG may be normal (if AV nodal conduction is faster that accessory pathway conduction to the ventricles) or abnormal, with varying degrees of preexcitation (depending how much of the ventricles are activated via the accessory pathway and how much via the normal AV node-His-Purkinje system).
The cardinal EKG features in sinus rhythm are (i) a short PR interval (<120 ms), (ii) a QRS duration of >120 ms with a slurred upstroke called a δ wave, and (iii) secondary ST-T wave changes.
In tachycardia, there may be:
- A narrow, regular QRS rhythm (orthodromic AV reentrant tachycardia, the most common variety) in which AV conduction is via the AV node. In these tachycardias, ventriculo-atrial conduction is via the accessory pathway. The retrograde P typically occurs just after the QRS in the ST segment or T wave.
- A wide, regular QRS rhythm due to either orthodromic AV reentry with rate-related bundle-branch block aberrancy, or (less common) antidromic AV reentrant tachycardia, in which antegrade AV conduction is via the accessory pathway, and retrograde ventriculo-atrial conduction is via the AV node.
- An irregular QRS rhythm due to atrial fibrillation; the QRS often varies between narrow and wide, as a consequence of either normal AV nodal conduction, rate-related bundle branch aberrancy or various degrees preexcitation of the ventricles via the accessory pathway.
Electrophysiologic study, required if undergoing catheter ablation

Differential Diagnosis

AV nodal reentrant tachycardia
Atrial tachycardia
Atrial flutter with 2:1 AV conduction
Junctional tachycardia
EKGs may mask or mimic MI ("pseudo Q waves"� due to negative δ waves), bundle-branch block, ventricular hypertrophy, accelerated idioventricular rhythm, ventricular bigeminy, and electrical alternans (the latter 2 diagnoses when accessory pathway conduction is intermittent).

Treatment

Medication

Acute management:
- To interrupt the reentry circuit:
  - Valsalva, and vagal maneuvers
  - Adenosine (IV), but watch for atrial fibrillation because it may lead to rapid conduction over the accessory pathway and precipitate ventricular fibrillation.
  - Although not approved for this indication, ibutilide is effective in blocking conduction in accessory pathways and may have a special place in the treatment strategy of patients with the WPW syndrome and atrial fibrillation.
  - IV procainamide may be used acutely because it decreases conduction over the accessory pathway and is safe if anterograde accessory pathway conduction is present in atrial fibrillation. However, IV procainamide may cause hypotension.
Chronic management:
- See comments regarding catheter ablation.
- Antiarrhythmic drug therapy:
  - Otherwise, a calcium channel blocker such as verapamil or a β-blocker can be used.
  - The class IC antiarrhythmic drugs flecainide and propafenone and the class III antiarrhythmic drug sotalol are effective and well tolerated.
Amiodarone, a class III antiarrhythmic drug, is potentially effective but its use is limited by adverse drug reactions.
Class IA drugs (quinidine, procainamide, and disopyramide) are of limited value due to frequent adverse drug reactions during long-term treatment.

Additional Treatment

General Measures

12-lead EKG is extremely important to secure the diagnosis
Digoxin: Not desirable drug because if atrial fibrillation occurs, there may be rapid conduction over the accessory pathway and induction of ventricular fibrillation
Cardioversion is indicated for acute management if atrial fibrillation occurs with rapid conduction over the accessory pathway, or if there is hemodynamic compromise. Cardiac arrest may occur during atrial fibrillation if there is rapid conduction to the ventricles via the accessory pathway inducing ventricular fibrillation.
Because of the problems of long-term drug administration (adverse drug reactions, problem of multiple daily doses/noncompliance, and failure at some time over years of treatment), catheter ablation has emerged as a (if not "the"�) treatment of choice for recurrent AV reentrant tachycardia:
- The procedure can be performed safely with a low risk for complications and a high degree of efficacy.
- Long-term, ablation is likely cost-effective and improves quality of life compared with drug therapy, especially with class IA and IC agents.
- Virtually all deaths attributed to accessory pathway conduction have occurred in patients with prior arrhythmia symptoms, and not as a 1st event.

Surgery

Surgery has been performed in the past. This has been superseded by catheter ablation for cure. �

In-Patient Considerations

Admission Criteria

Admission is usually not required.
Admission is warranted if supraventricular tachycardia is incessant or if there is a life-threatening associated problem such as atrial fibrillation with rapid conduction over an accessory pathway (shortest preexcited RR interval ≤250 ms, equivalent to a heart rate of ≥240 bpm).
RF catheter ablation of accessory pathways can be undertaken on a same-day admission schedule.

Ongoing Care

Follow-Up Recommendations

Patient Monitoring
General medical care if on drugs. If cured by catheter ablation, none. Recurrence can be prevented by either drug therapy or cure by catheter-based radiofrequency ablation. �

Patient Education

No specific dietary recommendations. Similarly, no specific activity recommendations, although arrhythmias can occasionally be precipitated by exercise and catecholamine increase. Otherwise, counseling relates to treatment options, especially opportunity for cure with catheter ablation. Vagal maneuvers to terminate arrhythmia can be taught. �

Prognosis

If accessory pathways are ablated and the heart is structurally normal, prognosis is normal. The prognosis is also excellent if accessory pathway has a long anterograde refractory period and cannot preexcite the ventricles rapidly during atrial fibrillation. �

Additional Reading

1Al-Khatib �SM, Pritchett �ELC. Clinical features of Wolff-Parkinson-White syndrome. Am Heart J. 1999;138:403-413. �[View Abstract]2Ganz �LI, Friedman �PL. Supraventricular tachycardia. N Engl J Med. 1995;332:162-173. �[View Abstract]3Jackman �WM, Wang �X, Friday �KJ. Catheter ablation of accessory atrioventricular pathways (Wolff-Parkinson-White Syndrome) by radiofrequency current. N Engl J Med. 1991;324:1605-1611. �[View Abstract]4Miles �WM, Klein �LS, Rardon �DP. Atrioventricular reentry variants: Mechanisms, clinical features, and management. In: Zipes �DP, Jalife �J, Cardiac Electrophysiology: From Cell to Bedside, 2nd ed. Philadelphia: WB Saunders, 1995;638-655.

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