Misleading 3D Activation Mapping post Cavotricuspid Isthmus Ablation

Background: High density 3D mapping for typical atrial flutter (AFL) ablation provides a highly detailed voltage and activation map.

Objectives: Describe misleading results of high density 3D activation mapping post cavotricuspid isthmus (CTI) ablation.

Methods: 3D electroanatomic voltage and activation mapping of the RA was performed in 15 consecutive patients (pts) with typical AFL, using the Ensite Precision (St. Jude Medical) with a Halo catheter pre and post ablation.

Results: Activation and entrainment mapping confirmed CTI dependent AFL in all pts. Mean number of map points was 611±312. Lateral low voltage areas were seen in 10 (62.5%) pts. Post ablation activation map during CS pacing (available in 6 of the 10) demonstrated latest activation on the lateral wall aligned with the low voltage areas and in 3(33.3%) pts this was later than just lateral to the CTI ablation line masquerading as a gap in the ablation line. However, bidirectional block was confirmed by differential pacing, widely split double potentials on the ablation line and non-inducibility. Failure to recognize this misleading activation map in 2 pts resulted in delivery of significantly more ablation lesions (34 vs. 19, p=0.0007). At follow-up of 4±3 months, there were no recurrences.

Conclusions: Areas of low voltage in the lateral right atrium may lead to slow conduction mimicking a gap in the ablation line. Comparing pre-ablation voltage to post-ablation activation map can identify areas of low voltage with slow conduction. The use of other maneuvers can prove bidirectional block and avoid further unnecessary RF delivery.