Predictive Parameters for Impending Steam Pops During High-Power Short-Duration Ablation for Atrial Fibrillation.

Background: High-power short-duration (HPSD) radiofrequency ablation (RFA) for atrial fibrillation (AF) treatment carries the risk of steam pops (SPs) due to rapid tissue heating. However, methods to predict impending SP during HPSD-RFA remain undefined.

Objective: This study aims to establish a quantitative criterion for predicting SPs during HPSD-RFA.

Methods: Retrospective analysis was performed on 489 patients undergoing HPSD-RFA for AF, focusing on corresponding RFA parameters in those who experienced SPs.

Results: Among 1943 ablation lesions (ALs) delivered in 18 patients with SPs, 24 ALs had SP occurrence. Tip temperature, RFA duration, and ablation index were not significantly different between SP ALs and non-SP ALs. The mean contact force was significantly higher in SP ALs (12 g vs. 9, p < 0.001). All SPs adhered to the following criteria: impedance drop ≥8Ω during the first 4 s of RFA, impedance variability <5Ω within the first 4 s of RFA (24/24 vs. 79/247, p < 0.001), no events in the posterior wall of the left atrium, impedance drop ≥12Ω within 4-12 s. By halting delivery of RFA early with this finding in approximately five ALs per patient, the risk of SP complications could be significantly mitigated.

Conclusion: Monitoring impedance trends in the initial 4 s of HPSD-RFA can effectively predict impending SP occurrences. Automated algorithms should be developed to halt RFA delivery in this setting.