Slow pathway and atrioventricular nodal bumping in the setting of cryoablation of atrioventricular nodal re-entry tachycardia

INTRODUCTION: Between 2005 and 2022, 364 patients were treated with cryoenergy for atrioventricular nodal re-entrant tachycardia (AVNRT). After we noticed that bumping of the slow pathway could occur a cohort of 68 consecutive patients, highly symptomatic, were prospectively studied between 2005 and 2008 for the occurrence of bumping of the slow pathway or other nodal structures during catheter manipulation. The analysis was stopped after 68 patients based on the results obtained. Slow pathway bumping was defined as the ability to induce sustained tachycardia at the baseline but not anymore after manipulation of the ablation catheter, before any energy delivery attempt was made, linked to slow pathway conduction impairment. METHODS AND RESULTS: In 63 patients a sustained tachycardia could repeatedly be induced at the baseline state when only diagnostic catheters were in place. In 20.6% of these patients (13 pat) bumping occurred. The bumping was linked to the slow pathway in 12 patients. CONCLUSIONS: Slow pathway bumping is a frequent phenomenon in the setting of cryocatheter ablation of AVNRT. It might explain the higher recurrence rate compared with radiofrequency (RF) when cryomapping is done during sinus rhythm rather than during ongoing tachycardia. It may also explain some cases of tachycardia non inducibility at the baseline. It also has implications when the ablation is done with radiofrequency current: in the case an accelerated nodal rhythm is absent after energy application but tachycardia is no more inducible slow pathway bumping may also be considered.