Background: Recently the efficacy and safety of a novel radiofrequency balloon (RFB) for pulmonary vein isolation (PVI) has been evaluated. The standard protocol for ablation with this balloon leads to a switch-off of the posterior electrodes after 20 seconds, compared to a duration of 60 seconds for the remaining electrodes. To reduce the risk of esophageal injury, we assessed a novel strategy which applied an earlier switch-off of the posterior electrodes based on the impedance drop.

Methods: Our new protocol implements a switch-off of the posterior electrodes after a local impedance drop of 12 Ohm, but at the earliest after 10 seconds. A total of 19 patients were treated with this new strategy to date. Patients were scheduled to receive an esophagoscopy one day after the procedure. Procedural data and the results of the esophagoscopies were compared to 131 patients who received the RFB PVI in our centre prior to the change of the protocol. 

Results: A total of 73 RFB applications were analysed. Posterior electrodes were switched off after a mean of 13.1 ± 0.9 seconds and reached an impedance drop of 24.4 ± 1.8 Ohm. Comparison of the new ablation protocol (NEW) to the standard protocol (STD) showed no significant difference in proportion of first pass isolation (NEW 75.7% vs STD 76.0%). However, an intraprocedural immediate reconnection of a pulmonary vein was observed in 4/73 (5.5%) applications after the early switch-off of the posterior electrodes. 

No esophageal lesions were detected in the patients treated with the new protocol (0%, 0/17), compared to 4,0% (3/75, p = 0.41) in our remaining patients and 8,2% (7/85, p = 0.21) in recently published data from two centres. No significant difference in percentage of intraprocedural esophageal temperature rise >39,0° C (NEW 11.6% vs STD 9.9%, p = 0.67) was observed. The amount of impedance drop of the posterior electrodes was no significant predictor for single-shot isolation or early reconnection.

Conclusion: In a first experience, a novel impedance-based switch-off strategy for the posterior electrodes of the radiofrequency balloon indicates a similar intraprocedural efficacy compared to the previous strategy. Numerical reduction of esophageal lesions suggests a potential benefit of the safety profile, but larger numbers of patients are needed to further assess this effect. The observation of immediate intraprocedural PV reconnections raises the question whether a higher impedance-drop threshold for the switch-off may be beneficial for durable PVI.