ventricle outside of the regular atrioventricular conduction system. Clinically, they may manifest as substrates for ventricular preexcitation. The first accessory pathway in a patient who suffered from Wolff-Parkinson-White syndrome was described in 1943 by Wood, Wolferth, and Geckler. 1 Shortly after, Öhnell created a reconstruction of an accessory pathway that very elegantly showed the close proximity of the pathway to the fibrous attachment of the mitral valve and its relationship with the sulcus coronarius (Figure, A). 2 Subsequent histological studies have demonstrated unequivocally that these pathways are the anatomic substrates for the classical Wolff-Parkinson-White variety of preexcitation.