Electrogram characteristics at successful cryoablation sites in slow-fast atrioventricular nodal reentrant tachycardia

Purpose: Cryoablation is a safe alternative to radiofrequency (RF) ablation for slow-fast atrioventricular reentrant tachycardia (AVNRT); however, optimal electrogram parameters for site selection remain unknown. We retro-spectively investigated local electrograms for slow pathway (SP) modification in cryoablation.Methods: Forty-five consecutive patients with slow-fast AVNRT who underwent cryoablation using a 6-mm-tip catheter were enrolled. Electrogram parameters for sites of successful SP modification (success-sites) were investigated; these included the interval between atrial activation at His and the last deflection of SP potential, defined as the His(A)-SPP interval. In 8 patients, 3-dimensional mapping by multi-electrode catheter was per-formed pre-ablation for more detailed SP assessment.Results: Twenty-seven of 45 patients had successful SP modification by 1 cycle of freeze-thaw-freeze cryoablation at a single site with a low amplitude and fragmented SP potential. Among a total of 76 cryoablation sites in all patients, the His(A)-SPP interval at success-sites (45 sites) was significantly longer than that at unsuccess-sites (31 sites) (86 +/- 9 vs.78 +/- 10 msec, p < 0.0001). The AV amplitude ratio was not significantly different be-tween success-and unsuccess-sites (0.21 +/- 0.22 vs.0.25 +/- 0.23, p = 0.429). The cutoff value of the His(A)-SPP interval for successful cryoablation was 82 msec with a sensitivity of 0.67 and specificity of 0.71 (AUC: 0.739; 95%CI: 0.626-0.852; p < 0.0001). Three-dimensional mapping in all 8 patients showed that sites with the most delayed atrial activation and the last deflection of the fragmented SP potential within the Koch's triangle coincided with success-sites.Conclusion: A longer His(A)-SPP interval and fractionated SP potential were characteristics of successful cryoa-blation for SP modification in slow-fast AVNRT.