Use of Tissue Electric and Ultrasound Characteristics to Predict and Prevent Steam-Generated Cavitation During High-Power Radiofrequency Ablation.

Abstract

Given a paucity of data, the aim of this study was to define predictors of steam pops (SPs) during open-irrigated radiofrequency ablation (RFA). SPs during RFA can lead to dire consequences, including perforation and stroke. In an exvivo bovine myocardium model, open-irrigated RFA was applied at 50 W for 60 s; intracardiac echocardiographic images for RFA with and without SPs was compared. Using an invivo porcine model, open-irrigated RFA was applied at 50 W for 60 s, and RFA parameters of SPs were analyzed. A retrospective analysis was performed of recorded SPs during clinical ablation procedures over a 1-year period. For RFA SPs, there was 32% greater intracardiac echocardiographic tissue echogenicity than for RFA without SPs (p< 0.001). In addition, RFA SPs had more rapid increases of tissue echogenicity, particularly in the last 5 s before SPs. Compared with RFA without SPs, RFA SPs had larger impedance reductions (33.0 ± 16.0 Ω vs. 23.0 ± 10.8 Ω; p=0.032). SPs were also associated with more rapid initial impedance reduction (1.40 Ω/s vs. 0.38 Ω/s for RFA withoutSPs; p= 0.001). Clinical SPs during ablation procedures had a significantly faster impedance reduction during the first 5 s of ablation compared with matched control ablations (15.7 ± 6.7 Ω vs. 8.1 ± 4.7 Ω; p< 0.0001). Certain echocardiographic and biophysical parameters during open-irrigated RFA are associated withincreased SP risks. These include greater tissue echogenicity, larger total impedance reduction, rapid rate ofinitialimpedance reduction, and rapid increase in tissue echogenicity.