Paroxysmal Supraventricular Tachycardias due to Accessory AV Pathways (Preexcitation Syndromes)

Two classic features of Wolff-Parkinson-White (WPW) pattern on ECG

• Short PR interval

• Wide, slurred QRS complex due to manifest preexcitation (delta wave)

Most patients with WPW pattern do not have clinical history of arrhythmia but have a higher risk of sudden cardiac death due to rapidly conducted atrial fibrillation through the accessory pathway

Risk factors

• Age younger than 20

• History of tachycardia

• Rapid conduction properties at electrophysiologic testing

Accessory pathways occur in 0.1–0.3% of the population and facilitate reentrant arrhythmias

Orthodromic reentrant tachycardia

• Accounts for ~ 90% of atrioventricular reciprocating tachycardia (AVRT) episodes

• Characterized by conduction antegrade down the AV node and retrograde up the accessory pathway, resulting in a narrow QRS complex (unless an underlying bundle branch block or interventricular conduction delay is present)

Antidromic reentrant tachycardia

• Conducts antegrade down the accessory pathway and retrograde through the AV node

• Results in a wide QRS complex

Atrial fibrillation or flutter with antegrade conduction down the accessory pathway and a rapid ventricular response seen in up to 30% of patients with Wolff-Parkinson-White syndrome

Some patients have a delta wave found incidentally on ECG

Exercise treadmill testing useful in determining if preexcitation is lost at rapid rates

Electrophysiologic testing with possible catheter ablation useful to ensure patients are not at an increased risk for syncope or sudden death

• Patients found to have the shortest preexcited R-R interval (SPERRI) during atrial fibrillation of ≤ 250 msec or inducible supraventricular tachycardia are at increased risk for sudden cardiac death

• Should undergo catheter ablation

For narrow-complex reentrant rhythms involving a bypass tract (orthodromic AVRT)

• Vagal maneuvers

• Intravenous adenosine

• Intravenous verapamil

For wide-complex tachycardia in the presence of an accessory pathway, be it reentrant-type (antidromic AVRT) or atrial fibrillation with antegrade conduction down the bypass tract

• Intravenous class Ia (procainamide) and class III (ibutilide) antiarrhythmic agents

  • Medications of choice

  • Increase the refractoriness of the bypass tract

• If hemodynamic compromise is present, electrical cardioversion is warranted

• Agents such as calcium channel blockers and beta-blockers should be avoided because of increased risk of ventricular fibrillation

Agents such as calcium channel blockers, and beta-blockers should be avoided

Amiodarone can be effective in refractory cases

If hemodynamic compromise is present, electrical cardioversion is warranted

Radiofrequency ablation is the procedure of choice for long-term management of patients with accessory pathways and recurrent symptoms

For patients not a candidate for catheter ablation, class Ic or class III antiarrhythmic medication may be considered