Safety and Efficacy Aspects of a Standardized Stepwise Anatomical Approach for AVNRT Ablation

This proposal aims to evaluate safety and efficacy aspects of a new protocol for AVNRT ablation, using a stepwise anatomical approach.

The investigators hypothesize that the use of a standardized electro-anatomical guided strategy, using a sequential approach as follows:

1. Right-side postero-septal tricuspid annulus
2. Coronary sinus
3. Left-side postero-septal mitral annulus

For slow pathway AVNRT ablation is safe and efficient, increasing the chance of a successful ablation in difficult cases, while reducing the need of re-do procedures and the risk for high-degree atrio-ventricular block.

The investigators aim to define and implement a new standardized protocol for AVNRT ablation while at the same time assessing the efficacy and safety of coronary sinus and left-side approaches for slow-pathway ablation.

Atrio-ventricular nodal reentrant tachycardia (AVNRT) is the most common form of supraventricular tachycardia in adults. The substrate of AVNRT is dual nodal atrio-ventricular (AV) physiology represented by the presence of slow (SP) and fast pathway (FP) conduction. Selective radiofrequency (RF) ablation of the slow AV nodal pathway can cure the arrhythmia with acute success rates varying from 95 to 98% and low recurrence rates during long-term follow-up.

The compact AV node sends two posterior extensions with node-like tissue distributed towards the coronary sinus and tricuspid annulus (right posterior extension) and towards the mitral annulus (left posterior extension). Earlier literature suggested that the right posterior nodal extension is involved in the tachycardia circuit of most patients with AVNRT (slow pathway input). The tachycardia circuit may rarely involve the left posterior nodal extension, in which case a left-sided ablation procedure is needed. The right-sided approach is sufficient for the majority of cases and represents today the standard protocol for AVNRT ablation.

Lee et Al., in view of current anatomical and electrophysiological knowledge concerning the AV node, proposed the following sequential approach for SP ablation:

I. the isthmus between tricuspid annulus and coronary sinus ostium (the usual site of slow pathway), II. the tricuspid edge of coronary sinus ostium (by moving the ablation catheter tip slightly in and out of the coronary sinus), III. the septum lower than coronary sinus ostium, moving higher up on the half of Koch's triangle along the septum, IV. one or two burns inside the first few centimeters of the coronary sinus, V. left side of the septum (last).

The investigators hypothesize that the use of a standardized electro-anatomical guided strategy, using a sequential approach as follows:

1. Right-side postero-septal tricuspid annulus
2. Coronary sinus
3. Left-side postero-septal mitral annulus

for slow pathway AVNRT ablation is safe and efficient, increasing the chance of a successful ablation in difficult cases, while reducing the need of re-do procedures and the risk for high-degree atrio-ventricular block.

The protocol will be applied in all patients undergoing slow pathway ablation for typical AVNRT. Those with unsuccessful right-sided attempt and who undergo coronary sinus and left-sided ablation attempt will be eligible for registry inclusion.

Eligibility Criteria:
Inclusion Criteria:

1. Age \> 18 and \<80 years
2. History of symptomatic PSVT
3. Signed informed consent
4. Documented AVNRT during EPS with at least 1 of the following:

   * Previous unsuccessful right-sided ablation attempt
   * Ideal SP electrogram at XR \< 10 mm in RAO 30°
   * Right-sided ablation attempt with:

     * VA block during JB or
     * A minimum of 7 unsuccessful RF energy deliveries, with no upper limit (to the 1st operator's discretion)

Exclusion Criteria:

* Previous CVA
* Severe mitral or aortic valve disease
* Documented intra-cardiac thrombus