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Wolff-Parkinson-White syndrome (WPW) is a supernormal conduction disorder; it is characterised by the presence of one or several accessory atrioventricular connections, which can lead to episodes of sporadic tachycardia. The mean prevalence is estimated at 1/450, thus this is not a rare disease. WPW syndrome mainly affects males (70% of cases), mostly at a young age. During foetal life, numerous connections link the atria to the ventricles, but they all disappear before birth except for one: the bundle of His. However, in some individuals, other connections may also persist. The positions of these accessory pathways vary from one patient to another. These accessory pathways bypass the atrioventricular node, leading to ventricular preexcitation and, in some cases, to episodes of tachycardia that either stop spontaneously or require treatment. Cardiac preexcitation can be associated with a heart malformation (such as Ebstein anomaly, see this term) or with isolated hypertrophic cardiomyopathy, or it can be part of Pompe or Danon disease (see these terms). Wolff-Parkinson-White syndrome can be sporadic or familial. The familial form is difficult to identify because the accessory pathways are not always permeable (active). It can be totally silent, either clinically (no tachycardia) or on the electrocardiogram (ECG). Mutations in the PRKAG2 gene have been associated with some familial forms of the Wolff-Parkinson-White syndrome. The diagnosis is often established as a result of rhythmic complications. In addition the rhythmic disorder, the ECG may show three of the following signs: lack of the atrioventricular slow pathway (short PR interval, <0.12 seconds), ventricular preexcitation (delta wave at the beginning of the QRS complex), followed by normal stimulation of ventricles (larger QRS complex > 0.12 sec from the beginning of the delta wave to the end of QRS). This type of ECG corresponds to an abnormal bundle directly connecting the atria and ventricles. If the bundle connects the atrium to the bundle of His, the ECG shows a short PR interval (<0.12 sec) with a normal QRS complex. This is a variant of WPW syndrome, described by Lown-Ganong-Levine. Differential diagnoses include complete bundle branch block, anterior and low-posterior infarct, ventricular extrasystoles and ventricular tachycardia with complications. As familial forms are rare and the disease is not particularly severe and responds to treatment, genetic counselling is usually not proposed. Some drugs, such as beta-blockers, are useful for the treatment of rhythmic complications and to prevent recurrence. However, digitalis drugs used alone are counter-indicated. Localised radiofrequency ablation is sometimes attempted. This procedure, carried out while the patient is awake, is quite long. It consists of guiding a probe into the heart via a vein, and identifying and destroying the accessory bundle. With the exception of a few cases of sudden death, life expectancy is generally not altered by the syndrome. |