Background: Despite the sustained efforts and advances in the fields of anatomy, histology, immunohistochemistry and cardiac mapping, the definition of the AVNRT circuit in humans is still incomplete. This discouraging result can be explained by many reasons, but the most important one has been the impossibility to map the AVNRT circuit without recording the electrical activity of the AVN and its extensions, which represent the diastolic interval in the tachycardia cycle. The aim of this study was to compare high density activation mapping integrated and not integrated with AV node potential recordings to establish the importance of annotation of AV nodal structure electrical activity in defining Koch’s triangle activation during AVNRT.
Methods: Electroanatomic 3-D reconstruction and propagation automated mapping of atrial activation during both sinus rhythm and tachycardia was performed using a basket catheter (64 electrodes of 0.4-mm2 area; 2.5-mm spacing, Orion, Boston Scientific, Natick, MA) and the Rhythmia electroanatomic mapping system in group 1 patients (X). In group 2 patients (45) the AV node potential (a very low frequency signal distinct from atrial, His bundle or ventricular activations, recorded from electrodes overlying the region of the compact AV node and its extensions by using a non-conventional bipolar electrogram filtering of [0.05/1 – 250] Hz) were also recorded both during slow fast AVNRT.
Results: The integrated map showed that during AVNRT, the activation wavefront descends from the Tendon of Todaro region (fast pathway area) and rises along the septal leaflet of the tricuspid valve through the RINE and reaches the AV bundle probably via the LNB bypassing the compact AV node almost completely. This kind of activation of the Koch’s triangle was not reconstructed by the non-integrated map. Moreover, the recording of the potentials of the AV node structures makes it possible to obtain a 100% coverage of the tachycardia cycle which was only 32% in the non-integrated maps (p < 0.0001).
Conclusion: The recording of the electrical activity of AV nodal structures allows a better definition of the circuit of typical slow-fast AVNRT which, in the majority of the cases, is completely localised in the right atrium.