<unk>  syndrome was originally thought to involve a rapidly conducting accessory pathway (bundle of James) that connects the atria directly to the bundle of His, bypassing the slowly conducting atrioventricular node. However, the majority of those with<unk>  in whom electrophysiological studies have been performed do not have any evidence of an accessory pathway or structural abnormality. Whilst in a minority of cases some form of intranodal or paranodal fibers that bypass all or part of the atrioventricular node can be found with subsequent conduction down the normal His-Purkinje system, in most cases the short PR interval is caused by accelerated conduction through the atrioventricular node.<unk>  syndrome is therefore felt to represent a clinical syndrome with multiple different underlying causes.
Lown–Ganong–Levine syndrome
Wolff–Parkinson–White syndrome
Lucey–Driscoll syndrome
Morgagni Stewart Morel syndrome
Bhaskar–Jagannathan syndrome
Claude's syndrome
Witteveen–Kolk syndrome
Townes–Brocks syndrome