PO-04-111 IDENTIFICATION OF THE SLOW AV NODAL PATHWAY BY LOW FREQUENCY MAPPING

The slow nodal pathway is the current target for ablation in patients with AV nodal reentrant tachycardia (AVNRT). Proper identification of this pathway from the fast nodal pathway is important to avoid AV nodal conduction prolongation or block. Slow conduction has been associated with low-frequency electrograms (EGMs) in some experimental models. However, this has been never evaluated clinically. To evaluate if sites of ablation of the SNP can be properly identified by frequency mapping. Consecutive patients with common AVNRT were included in the study. Bipolar voltage and activation maps were generated with a regular 4 mm tip catheter. Peak frequency maps (PF) were computed online prior ablation and displayed on the activation map with shadowed areas where PF was <200 Hz (figure, left panel). Focal radiofrequency application (RFa) was directed to the areas of late activation (figure, left panel) and low frequency (figure, right panel) (LA-LF). The slow nodal pathway was considered ablated if junctional rhythm was recorded during RFa and AVNRT was no longer inducible afterwards. 20 patients (48 ±15 years, 15 female) were enrolled in the study. A late activation low frequency area of 0.92±0.48 cm2 was found in 18 of them. The mean PF at this area was 175.5 ± 37.1 Hz (analysis per patient) and 170.1 ± 48.10 Hz (analysis per recording site) which was significantly lower than the PF recorded at the adjacent atrial area (279.71 ± 28.11 Hz per patient, 279.91 ± 69.47 Hz per recording site) (P<0.0001). RFa at the late activation low-frequency area induced junctional rhythm in 17 patients. AVNRT was no longer inducible after this in all 17 patients. Additional RFa were often given to reinforce the result (11 ± 9 RFa, 4.03 ± 3.35 min RFa time) The slow nodal pathway is often located in an area of late activation and low frequency.