Changing QRS Morphology in a Patient with Wolff-Parkinson-White Syndrome

Arrhythmias Involving Variants of Accessory Pathways

In some cases, atrioventricular reentrant arrhythmias are sustained by accessory pathways with peculiar electrophysiologic properties related to their specific anatomy. Most of these fibers, which may be responsible for variants of ventricular preexcitation, show decremental conduction properties due to a nodelike aspect or a peculiar tortuous anatomic route across the atrioventricular groove. Moreover, some fibers do not actively sustain any reentrant circuit and can be only involved as bystander in other arrhythmias. Although rare, these accessory pathway variants should be properly diagnosed using noninvasive and invasive methods to guide catheter ablation procedures when needed.