AV Nodal Reentrant Tachycardia Study

HYPOTHESES: 1. The Tendon of Todaro forms a line of block during slow/fast AVNRT preventing the atrial impulse from entering the triangle of Koch (and perhaps providing sufficient time for activation to pass through the coronary sinus coat to activate the posterior extensions of the AV node as is critical to maintenance of tachycardia) 2. The coronary sinus myocardial coat participates in all of the forms of AVNRT. The reentrant circuit is thus not confined within the triangle of Koch and sites remote from the compact AV node could be targeted for ablation reducing the risk of AV conduction block. 3. A model of the reentrant circuit can be created for each patient's tachycardia, using the site of earliest retrograde activation to suggest the retrograde limb and the resetting response to suggest the anterograde limb. DATA ANALYSIS/STATISTICS: Resetting and Mapping of AV nodal reentrant tachycardia: Pacing will be analyzed to see at which sites, the tachycardia can be reset by the latest extra-stimuli (i.e., with the least advancement in local activation). The coupling interval will be compared to the latest extra-stimulus capable of resetting (advancing) the tachycardia from the postero-septal tricuspid annulus. Ablation Results: The patients will act as their own reference, since the standard ablation technique in the postero-septal space is being performed first and tested for efficacy. The McNemar test will be applied to compare the efficacy of ablation at the postero-septal tricuspid annulus alone (standard ablation), with the efficacy of this ablation plus ablation within the coronary sinus. From our initial observations, It is anticipated that the additional ablation in the coronary sinus will increase the efficacy of the procedure from \<95% to \>98%, such that 100 cases should provide sufficient data to reach statistical significance.