Atrio-ventricular nodal re-entrant tachycardia ablation step by step low fluoro approach to prevent unexpected AV block

Abstract

Abstract Background Slow pathway (SP) radiofrequency (RF) ablation of AVNRT has a success rate of more than 98%, but up to 2% risk of unpredictable and frustrating AV node block despite the energy being delivered to the posterior aspect of Koch's Triangle (KT) which is far from the recorded His signal. A possible explanation is an atypical location of the AV node. KT pace-mapping (KTPM) has been demonstrated to be useful to recognize when AV is abnormally located in the mid or posteroseptal aspect of the KT. In these cases cryoablation would be the best choice because it is a well-established technique for the successful treatment of AVNRT with no complications reported but with a recurrence rate around 10% at long-term follow-up. Voltage bridge mapping (VBM) is a validated and effective technique in guiding cryoablation of AVNRT, with a complete acute success rate and no recurrences at mid-term follow-up. Aim To evaluate our low-fluoro step-by-step approach for AVNRT ablation including KTPM and VBM aiming to eliminate the risk of unpredictable AV node block. Methods The right atrium and coronary sinus electroanatomical mapping was done and diagnostic catheters were positioned at His and coronary sinus. After AVNRT diagnosis, 3D KTPM was performed. We developed it according to the “conventional” one in order to evaluate and visualize atypical AV node location during low-fluoro procedures. This was achieved by stimulating with the mapping catheter in the anteroseptal, posteroseptal and midseptal region respectively. Each point has been collected on 3D System measuring the interval between the stimulus to the His deflection (Fig. 1A–C). Voltage bridge-mapping was also performed, and both have been used as reference for SP RF ablation. If 3D KTPM showed a posterior extension of the AV node, then ablation was performed using cryo-energy aiming to reduce the risk of permanent AV node iatrogenic block. Methods and results 71 consecutive patients (mean age 61.0±14.5 SD, 46% female) undergoing low-fluoro ablation of AVNRT by 3D mapping system. KTPM was achieved in all the patients. In the 67 (94.3%) pts who showed superoparaseptal location of the AV node RF ablation was successfully performed. In 4 (5.7%) pts with midseptal extension of the AV node (Fig. 1D) a voltage-bridge mapping guided cryo-ablation was successfully performed (Fig. 1E). The mean procedural time was 95±18 SD min. Mean fluoro time was zero. After a mean follow-up of 28.5±16.7 SD moths, neither recurrences nor complications were recorded. Conclusion This is the first study to show how a tailored low-fluoro AVNRT SP ablation approach including 3D-PM of KT and VBM could be helpful to eliminate the risk of unpredictable and frustrating AV block. Our preliminary results would possibly encourage larger cohort, multicenter studies. Funding Acknowledgement Type of funding sources: None.