Abstract 15780: Duplication of the Conduction System in Heterotaxy Syndrome Delineated Using Remote Magnetic Navigation and Three-Dimensional Mapping
Introduction We investigated the presence of duplicated conduction systems in post-surgical adults with heterotaxy syndrome/atrial isomerism using remote magnetic navigation and 3D electro-anatomical mapping.
Method Dual AV nodes were identified when two different conducted QRS complexes were observed, preceded by their own His bundle potential. Sequential mapping was performed during spontaneous supraventricular rhythms or atrial pacing, as well as during sustained twin AV nodal reentrant tachycardia.
Results Out of a cohort of 8 adults with atrial isomerism, duplicated AV nodes were observed in 3. In 2 patients with right and left atrial isomerism respectively, the anatomical background included complete AV septal defect and they were both able to sustain twin AV nodal reentrant tachycardias. The two AV nodes were located at the superior and inferior aspects of the common AV junction respectively. They were interconnected by a sling of conduction tissue identified along the ventricular border of the AV septal defect by Purkinje-like potentials. In each case, at least one AV node exhibited bidirectional conduction and represented the antegrade limb of the circuit, whereas the remaining AV node represented the retrograde limb. In the third patient without AV septal defect, two completely separated electrical systems were identified on each side of the septum connected to their own branch, resulting in a left or right bundle branch block QRS morphology. No connecting conduction tissue between the AV nodes was identified and there was no retrograde VA conduction. Twin AV nodal tachycardia was not inducible.
Conclusion: In patients with heterotaxy syndrome, the presence of a duplicated AV node system connected by a sling of conduction tissue on a background of AV septal defect sets the scene for re-entry between the two nodes. With complete separation of the two AV nodes, internodal reentry was not demonstrated.
- © 2012 by American Heart Association, Inc.