Wolff-Parkinson-White (WPW) Syndrome

Ventricular preexcitation associated with a short P-R interval and a wide QRS complex.

Incidence 1 to 3:1000 in a general population.

Unclear, an autosomal dominant inheritance is suggested by some kindreds. Can be caused by mutation in the gamma-2 regulatory subunit of AMP-activated protein kinase (PRKAG) located on 7q36.

During fetal life, numerous connections link the atria to the ventricles, but they all disappear before birth except for the bundle of His. Sometimes, some of the connections do not disappear. This accessory pathway(s) characterizes the Wolff-Parkinson-White syndrome. An accessory atrioventricular connection (bundle of Kent) bypasses the atrioventricular node, and inserts directly into myocardium (consistent with bypass tracts in Lown-Ganong-Levine syndrome). The accessory bundle may conduct anteor retrograde. Antegrade conduction causes early commencement of ventricular depolarization, seen as a delta wave on the ECG. Retrograde conduction allows a reentry circuit to develop and is a mechanism for paroxysmal tachycardia generation. The accessory connection may only conduct in a retrograde direction; therefore a delta wave will not appear on ECG. Such a tract is described as concealed. In atrial fibrillation, antegrade conduction along the accessory pathway may result in rapid ventricular rate, which is poorly tolerated.

History, ECG findings of a short P-R interval, and a delta wave. Electrophysiology studies to define individual pathway anatomy and mechanism for dysrhythmia generation.

May be asymptomatic. Symptoms include palpitations (paroxysmal episodes of supraventricular tachycardia or atrial fibrillation), shortness of breath, feeding difficulties in infancy, syncope and chest pain. In infancy, WPW tends to improve in the first year of life and may be associated with Ebstein anomaly. Sudden death secondary to dysrhythmia may occur. Type A WPW demonstrates a large R wave in leads V1 and V2. In type B WPW, the S or QS waves predominate in leads V1 and V2. Supraventricular tachycardias may be managed by verapamil (potent negative inotrope), beta blockade, amiodarone, adenosine or cardioversion. Adenosine is said to achieve cardioversion in up to 87% of narrow complex tachycardias associated with WPW. Catheter or surgical ablation of pathways or pacemakers may also be indicated.

Obtain a history of frequency of dysrhythmia, and current treatment regimen. Continue antidysrhythmic drugs perioperatively. Review results of electrophysiology studies if available. Preoperative ECG mandatory. Pacemaker details if used to control supraventricular tachycardia (atrial overdrive pacing). Correct any electrolyte disturbance (sodium, potassium, and magnesium).

Minimize perioperative catecholamine surges; premedication may be beneficial. Perioperative beta blockade has been used. Atropine premedication, however, is relatively contraindicated. Use a technique to minimize risk of hypoxia, hypercarbia, or acidosis, all of which render cardiac muscle membranes unstable and ectopic depolarization more likely.

Enflurane is the volatile agent, which is probably least likely to induce arrhythmia. Halothane should be avoided (proarrhythmogenic, myocardial depressant). Desflurane has a sympathomimetic effect, which is undesirable. Sevoflurane has been used and reported to be appropriate. Propofol has no effect on the refractory period of normal and accessory tissue, thus it is useful for electrophysiology studies and ablation procedures. Pancuronium is relatively contraindicated. Extreme care if administering beta blockade to a patient already taking verapamil (may precipitate heart block). If atrial flutter or fibrillation is the cause of tachycardia, digoxin and verapamil are contraindicated because they may decrease the accessory pathway refractory period and exacerbate the tachydysrhythmia.