Septal accessory pathway: Anatomy, causes for difficulty, and an approach to ablation

Accessory pathway (AP) ablation is one of the most satisfying invasive electrophysiology procedures associated with high success rates and relatively few complications. Nevertheless, when APs are found on the cardiac septum, ablative procedures become complex, and unique pitfalls need to be avoided. These difficulties with septal ablation are magnified in the pediatric population. The relatively small heart, rapid nodal conduction, and proximity of the arterial system specifically complicate septal ablation in children. The electrophysiologist must use every tool in his or her armamentarium, including exact delineation of pathway location, identification of pathway potentials, detection of the presence of pathway slant, etc. In addition, an exact knowledge of the complex anatomy of the cardiac septum, including the posteroseptal space, the aortic cusp region, and the proximity of the AV conduction system and coronary vessels, becomes mandatory. In this review, we describe the developmental anatomy and regional anatomy of septal accessory pathways. We then discuss approaches to map specific to pathways in particularly problematic regions at or near the septum, including venous and aortic cusp related accessory pathways.