Electroanatomical properties of the superior vena cava - the vein, born for isolation

Abstract Background Superior vena cava (SVC) is a known source of non-pulmonary vein (non-PV) triggers. SVC isolation (SVCI) plays an important role in treatment of atrial fibrillation (AF). However, the proximity of the phrenic nerve and sinus node poses the potential risk of adverse effects and moreover, circumferential ablation can lead to SVC stenosis. Aims To assess the electroanatomical properties of SVC and to determine the optimal approach of the SVCI and its safety. Methods All patients who underwent high-density (HD) mapping of the right atrium (RA) and (SVC) with a multipolar mapping catheter between 01/2022 and 09/24 were prospectively included. In case of isolated PVs or presence of non-PV triggers SVCI was performed. The following mapping characteristics were defined: (1) sinus node (SN) area (area of earliest 10 ms activation time), (2) conduction block (CB) lines (difference more than 20% in activation time in 2 adjacent points) and (3) preferential RA to SVC conduction (defined by LAT velocity vectors algorithm) and (4) phrenic nerve (PN) location (by pacing with high output). Segmental SVCI (50W) was performed between CB lines. Systematic analysis of electroanatomical as well as ablation characteristics of the RA-SVC junction was performed (Figure1). Results 59 patients (42% female; 47% persistent AF) were included and in 21 (36%) patients SVC isolation was performed. The SN zone area was 1.05 (IQR 0.7-2.73) cm2 and was always separated from the SVC with a CB line. In 23 cases (87%) CB lines with 1-2 gaps were identified, with a total length of the gaps of 25.2 (15.45-38.83) mm between CB lines. In 23 cases (87%) CB lines with 1-2 gaps were identified, with a total length of the gaps of 25.2 (15.45-38.83) mm. Most gaps were in posterior segment (81%) (Figure 2D). PN capture could be achieved in 40 (68%) of patients, with PN length of 21.9 (IQR 15.6-30.3) mm and dominant PN location in the RL segment in 39 (98%) of patients (Figure2B). The distance from PN to the ablation line (AbL) was 8.7 (IQR 5.5-11.2) mm; an overlap of AbL and PN was observed in 2 (9.52%) of cases. Distance from the AbL to the SN was 7.9 (IQR 5.78-11.85) mm; in 1 case (5%) the AbL crossed the SN area in the RL segment. Velocity vectors represented the conduction from the RA to the SVC more selective than gaps with the width of 9.6 (IQR 6.25-19.2) mm. Due to presence of CB lines, there were no cases where circulation CA of the SVC was performed. The mean length of AbL was 27.6 (IQR 18.2-45) mm with a mean of 9(IQR 4-12) applications. SVCI could be achieved in 100% of patients (21 of 21 cases). No peri- or postprocedural complications occurred. Conclusion Modern mapping algorithms allow SVCI by segmental ablation in all cases. No phrenic nerve or SN damage have occurred by targeting gaps between the conduction block lines.