Definition
It is a syndrome in which there is an accessory pathway that bypasses the AV node and connects the atrium and ventricle (by bundles of Kent). May be associated with other congenital anomaly, commonly Ebstein anomaly.
Types
It is of 2 types:
1. Type A—accessory pathway on the left side (in ECG, tall R in V1 and V2).
2. Type B—accessory pathway on the right side (in ECG, deep Q in V1 and V2).
Clinical Features
• May be asymptomatic.
• May present with palpitation, paroxysmal attack of atrial or supraventricular tachycardia (most common) due to re-entry circuit, atrial fibrillation.
• Syncope.
• Sudden death (due to atrial fibrillation).
• Rarely—features of ventricular tachycardia, ventricular fibrillation.
Investigations
1. ECG shows—
–– PR interval short (<0.12 second).
–– QRS—wide.
–– Delta wave—in the upstroke of QRS (slurred QRS).
–– Q wave—may be present in lead II, III and aVF (confused with inferior myocardial infarction).
2. Electrophysiological study.
Treatment
1. If asymptomatic—no treatment is required.
2. If symptomatic—
–– Transvenous radiofrequency catheter ablation of accessory pathway is the specific treatment.
–– If this is not available—prophylactic antiarrhythmic drug should be given (β-blocker, amiodarone, flecainide, propafenone). These drugs prolong refractory period of accessory pathway.
–– Previously, surgical resection of accessory pathway used to be done.
3. Treatment atrial fibrillation with WPW syndrome—It is a medical emergency. Sudden death may occur. Treatment is as follows:
–– If troublesome symptoms—DC shock should be given. If not available, IV flecainide.
–– Radiofrequency ablation of abnormal pathway.
–– Drugs that slow down the conduction of accessory pathway may be used—amiodarone, flecainide, disopyramide, sotalol, etc.
Drugs to be Avoided in WPW Syndrome
Digoxin and IV verapamil. These drugs shorten the refractory period of accessory pathway.
Digoxin blocks the AV node and increases the conduction through the accessory pathway.
So, it increases the heart rate. Verapamil may cause same effect. It may precipitate ventricular
fibrillation.