Efficacy of cryo-ablation during atrioventricular nodal reentrant tachycardia

Because of the low atrioventricular (AV) block risk during cryo-ablation, it has become possible to treat AV nodal reentrant tachycardia (AVNRT) during arrhythmia. This study aimed to investigate the clinical outcomes of performing cryo-ablation for AVNRT during arrhythmia. Twenty-three patients with AVNRT treated by cryo-ablation during arrhythmia were enrolled. Cryo-ablation was performed gradually from the bottom to above the paraseptal tricuspid annulus until AVNRT was terminated. If the slow pathway was not eliminated despite cryo-ablation terminating the AVNRT, additional cryo-ablation was performed at a higher site until the slow pathway elimination was achieved. AVNRT was terminated by cryo-ablation in all 23 patients. However, the slow pathway was only eliminated in 6 patients. Among the remaining 17 patients, the slow pathway could not be ablated because transient AV block occurred during cryo-ablation at a higher site in 8 patients; however, cryo-ablation at a higher site successfully eliminated the slow pathway in the other 9 patients. In these 9 patients, the distance from the bottom of tricuspid annulus to the site of slow pathway elimination was significantly longer than that from bottom of tricuspid annulus to the AVNRT termination site (20.1 ± 5.3 vs 14.7 ± 4.5 mm: p = 0.027). During follow-up, AVNRT recurrence was confirmed in 3 patients. In 1 of these 3 patients, even a slow pathway elimination was achieved by cryo-ablation at the AVNRT termination site. The AVNRT termination site may not be the ideal site for performing cryo-ablation.