For ablation of AVRT, the typical target is the site of earliest fusion where atrial and ventricular activations are nearly simultaneous. Which option best describes this target?

For ablation of AVRT, the typical target is the site of earliest fusion where atrial and ventricular activations are nearly simultaneous. Which option best describes this target?

• A. Earliest atrial activation
• B. Site of earliest fusion A and V
• C. Near the AV node
• D. Distal His bundle

Answer: (B)

When mapping AVRT you’re looking for the exact point where the retrograde conduction through the accessory pathway meets the normal conduction to produce the atrial activation. The best target is the site of earliest fusion between atrial and ventricular activations, because that fusion zone marks the insertion point of the accessory pathway on the AV annulus where the pathway actively participates in the circuit. Ablating there interrupts the retrograde limb of the reentry loop, reliably eliminating AVRT. Why not focus only on the earliest atrial activation? That can point to the atrial insertion but may miss the true pathway connection where both chambers contribute to activation. Targeting near the AV node or the distal His bundle risks damaging the normal conduction system and is not the mechanism driving the arrhythmia. The fusion site best localizes the pathway itself and offers a safe, effective ablation target.

When mapping AVRT you’re looking for the exact point where the retrograde conduction through the accessory pathway meets the normal conduction to produce the atrial activation. The best target is the site of earliest fusion between atrial and ventricular activations, because that fusion zone marks the insertion point of the accessory pathway on the AV annulus where the pathway actively participates in the circuit. Ablating there interrupts the retrograde limb of the reentry loop, reliably eliminating AVRT.

Why not focus only on the earliest atrial activation? That can point to the atrial insertion but may miss the true pathway connection where both chambers contribute to activation. Targeting near the AV node or the distal His bundle risks damaging the normal conduction system and is not the mechanism driving the arrhythmia. The fusion site best localizes the pathway itself and offers a safe, effective ablation target.