Abstract
A high-risk left-sided posterolateral manifest accessory pathway (AP) was identified in a 49-year-old man. Two prior ablations had failed. A repeat procedure using 3D electroanatomic mapping demonstrated an extremely oblique AP. The earliest atrial activation site was not amenable to endocardial ablation. The earliest ventricular activation site was identified, demonstrating an AP with an extremely slanted course. Radiofrequency ablation here resulted in sustained bidirectional AP block. In challenging AP ablation cases, recognition of the potential for an oblique AP and the use of electroanatomic mapping may be beneficial.