Stepwise Approach for an Anatomic Guided Ablation of AVNRT

(Published from the AVNRT chapter by Drs. Von Bergen and Law, with permission from Fluoroscopy Reduction Techniques for Catheter Ablation of Cardiac Arrhythmias – Razminia, Zei)

Begin the study with creation of right atrial geometry. The His bundle should be labeled and the CS geometry separated.

Study participants will be randomized into one of two groups, the Voltage/Propagation mapping approach, or the Anatomic Guided approach.

The Voltage/Propagation mapping approach

Create an accurate geometry of right atrium and Triangle of Koch (TK) area.

Mark His location

Obtain atrial voltage and timing points during sinus rhythm (consider a multipole catheter for mapping)

Confirm atrial signals accuracy of timing and amplitude, delete ectopic/junctional beats
At least 35 points are recommended on the TK surface, with some voltage points surrounding the TK

Evaluate the local activation timing (LAT) and propagation wave. This is done evaluating the isochronal map for the late activation or by evaluating the propagation wave at the site of wave collision. The propagation wave can often be seen with progressing towards the TV with late signals in the TK, resulting in a wave collision. Mark the late activation using the isochronal map or the wave collision as seen in the movie demonstration to allow reference to the site while observing the voltage map.

Select site of ablation over a low-voltage area (typically 0.1 to 0.5mv), at or slightly superior to the wave collision/late activation area. If there are multiple locations, choose a location closer to the ventricular side of the TK.

- Confirm adequate distance from the His signals prior to ablation, and monitor PR interval throughout.
- Consider incorporation of “traditional” slow pathway circuit information (anatomic location, AV ratio, low amplitude signals)
- Choose a site with low voltage and late activation, most commonly near the Tricuspid valve.

Deliver test ablations to evaluate for effect. If using cryotherapy, consider ablation during AVNRT while monitoring for effect.

If there is no effect on the arrhythmia within 20s, then stop the ablation and consider an alternative location.

Adjust catheter position and preform test application in next location, typically first concentrating on promising areas in the low TK prior to locations closer to the His bundle. Preferentially select low-voltage sites near the wave collision first.

At a site of effect, consider a 4-5 min cryothermal application, or appropriate duration for RF energy. Insurance applications as appropriate should be placed at and around the site of successful ablation

Repeat testing on and off isoproterenol with use of appropriate end points

The Anatomic Approach

Place ablation catheter in anatomically appropriate area directed using anatomic and electrogram guidance.

Typically begin low in the TK
Consider evaluating for low amplitude, long duration atrial signals
Identify A:V ratios areas of 1:10 to 1:2

Deliver test ablations to evaluate for effect. If using cryotherapy, consider ablation during AVNRT while monitoring for effect.

If no effect with the test application

Adjust catheter position and preform test application in next location, with applications near the low TK prior to advancing to locations closer to the His bundle.

Use appropriate end points with post ablation testing on and off isoproterenol