accessorypathway

An accessory pathway is an anomalous conduction pathway between the atria and ventricles that bypasses the normal AV node-His-Purkinje system. Such pathways can conduct electrical impulses in one or both directions and may support atrioventricular reentrant tachycardias or facilitate pre-excitation.

In many cases the pathway is present but asymptomatic. When antegrade conduction occurs during sinus rhythm, it can produce pre-excitation on the electrocardiogram, most characteristically a short PR interval, a slurred upstroke of the QRS (delta wave), and a wide QRS complex. The most well-known clinical syndrome is Wolff-Parkinson-White (WPW) syndrome.

Anatomical types include congenital AV accessory pathways (Kent bundles) that connect the atria and ventricles directly; Mahaim fibers (atriofascicular or nodofascicular fibers) with decremental conduction properties; and fasciculoventricular or nodoventricular connections.

Diagnosis is based on ECG features and electrophysiology studies. Management ranges from observation in asymptomatic individuals to catheter ablation in symptomatic patients or those with high-risk pathway properties. Catheter ablation, usually using radiofrequency energy, aims to eliminate the pathway and has high success rates with low recurrence. Medications may be used to suppress tachyarrhythmias when ablation is not suitable.

History: Wolff-Parkinson-White syndrome describes the combination of pre-excitation with paroxysmal tachycardias due to an accessory pathway; the term is named for doctors Wolff, Parkinson, and White who described the phenomenon in 1930.