724-4 Coexistence of Typical and Atypical Atrio-ventricular Nodal Reentry: Evidence for Multiple Pathways of Slow Conduction

Abstract

The nature of the atrio-ventricular nodal (AVN) reentry circuit is still a source of debate. We studied two patients in which both typical (slow-fast, SF) AVN reentrant tachycardia and atypical (fast-slow, FS) AVN reentrant echoes could be elicited with atrial and ventricular stimulation respectively. Discontinuous antegrade and retrograde AVN curves were present in both patients, as shown below: The earliest atrial activation during SF reentry was recorded at the His bundle electrogram, while during FS reentry it was recorded anterior and inferior to the coronary sinus ostium. A single radiofrequency (RF) application at the earliest atrial site during FS reentry eliminated both the FS echoes and the retrograde discontinuous curve, while maintaining a discontinuous antegrade curve (figure) and SF reentry (non sustained in one patient and sustained in the other patientl. In the latter patient, complete elimination of the slow pathway and SF reentry was achieved by further RF applications approximately 1 cm above the ablation site for FS reentry. Prevention of atypical AVN echoes does not necessarily abolish the typical form of AVN reentry. This suggests that the atypical form is not simply a “reverse” of the typical form of AVN reentry.