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.

Inclusion Criteria:

- Ages 16-80

- At least one documented episode of AV nodal reentrant tachycardia

- Patient scheduled for electrophysiology study and catheter ablation for
supraventricular tachycardia

Exclusion Criteria:

- Ages < 16 or > 80

- Medical condition significantly increasing risk of extending procedure time or X-ray
exposure

- Pregnancy

- Prior ablation with radiation exposure >2 hours

- Electrophysiology study performed without sedation or anesthesia

- Unavailable for follow-up