Impact of pulsed-field ablation of the right superior pulmonary vein on conduction block in the superior vena cava

Background Low-voltage area (LVA) in the superior vena cava (SVC) have been reported after pulsed-field ablation (PFA) for the right superior pulmonary vein (RSPV). However, conduction delay in the SVC has not been systematically investigated. Purpose This study aimed to examine the impact of PFA on the RSPV concerning conduction in the SVC and to analyze the contributing factors. Method Patients with AF who underwent pulmonary vein isolation (PVI) using PFA were enrolled. High-density right atrial-SVC mapping during coronary sinus pacing (100 pacing per minutes) was performed before and after ablation. The distance between the SVC and RSPV ostium was measured on the horizontal section of the CT scan. LVA was defined as < 0.5 mV covering ≥ 0.5 cm². We have set up the color contour to show fifteen distinct colors, with each one indicating a 10 milliseconds interval, ranging from the earliest to the latest activation site. Conduction block was defined as the spectrum spanned 3 colors or more within 3 mm. Results A total of 69 patients (71.0 [66.0, 77.0] years old, 19 [27.5%] female, 45 [63.8%] hypertension) were included. 58 patients treated with PulseSelect, and 11 patients treated with Farapulse catheters. Before ablation, conduction block at the anterior SVC wall was present in 31 (44.9%) patients. After ablation, development of LVA was observed in 26 (37.7%) patients. Among them, 11 patients did not develop conduction block (Figure 1A), defined as Group 1, and 15 patients developed conduction block (Figure 1B). Among the patients without LVA development, a conduction block was observed in 16 individuals (Figure 1C). Patients with conduction block development were defined as Group 2, and without any changes as Group 3 (Figure 2). In the univariate analysis of factors predicting the impact on SVC, patients without hypertension (8 [72.7%] vs. 13 [41.9%] vs. 4 [14.8%], p < 0.01), smaller left atrial diameter (36.3 [34.5, 45.4] vs. 39.2 [36.6, 44.8] vs. 43.5 [40.8, 46.8] mm, p < 0.01), and shorter distance between the SVC and RSPV (2.69 [2.10, 3.80] vs. 3.87 [3.04, 4.41] vs. 5.27 [4.90, 6.65] mm, p < 0.001) showed a significant impact. In multivariate analysis, shorter distance between RSPV and SVC was the only predictor of SVC impact. Among the patients with LVA, 20 patients LVA development at the lateral wall despite the absence of direct energy application. In these cases, there was a tendency for a higher incidence of pre-existing anterior SVC wall conduction block (16 [80.0%] vs. 2 [33.3%], p = 0.051). In addition, 2 patients underwent redo procedure. Patient with conduction block without LVA development had disappeared conduction block (Figure 1D), and patients with LVA without conduction block still had LVA. Conclusions PFA for RSPV isolation can induce SVC conduction block even without LVA development. Distance between RSPV and SVC was the only predictor of SVC impact.