Background: A novel irrigated RF balloon (RFB) for pulmonary vein isolation (PVI) was released in selected centres. It is a 28 mm open irrigated balloon with 10 unipolar electrodes on its surface to deploy a circular ostial lesion set around the PVs. Varying the flush rate can result in different compliance of the RFB. During the ablation phase, the flush rate was initially fixed at 35 ml/min. A recent upgrade allows now the operator to ablate with a reduced flush at 25 ml/min.

Methods: Data from consecutive RFB procedures were collected and analysed. Sequential PVI was performed using the RFB: each application lasted 60 seconds, the posterior electrodes were identified to stop the energy delivery after 20 seconds. After the introduction of the updated RF generator, all patients were treated with 25 ml flush rate to increase the compliancy of the RFB (Group-25). The patients previously treated with a 35 ml fixed flush rate served as a control group (Group-35). To exclude a learning curve effect the analysis was repeated including only the last patients in Group-35. Acute procedural data and complications were collected, focused on the rate of single shot PVI (ssPVI) recorded in the two groups.

Results: Data from 106 consecutive RFB procedures were analysed: 28 patients were included in Group-25 and 78 in Group-35. Baseline characteristics were similar between the two groups. First pass ssPVI was achieved in overall 66% of targeted PVs, more frequently in Group-25 compared to Group-35 (75% vs 62% - p=0,014). This difference was driven by a reduced rate of early reconnection after the first application in Group-25 (14% Vs 26%, p=0,013) and particularly by an increase in the rate of ssPVI in the left superior PVs (74% vs 52%, p=0,048). Less applications per PVs were overall needed in Group-25 (1,2±0,3 vs 2,1±1,1 p= 0,001), and a significant reduction of procedure (49±17 vs 64±20 min, 0=0,001) and fluoroscopy time (6±2 vs 10±4 min, p<0,001) was achieved. A single phrenic nerve palsy was observed in the Group-25. The analysis was repeated comparing Group-25 only the last 28 patients in Group-35, still recording a similar increase in the rate of ssPVI (75% vs 63%, p=0,046).

Conclusion: The introduction of a lower irrigation rate during ablation led to an increased efficacy of the novel irrigated RFB for PVI. The overall rate of single shot PVI with the RFB now reaches 75%, with a reduced rate of early reconnections and an increased rate of single shot isolation of the LSPV.