Impact of baseline pool impedance on lesion metrics and steam pops in catheter ablation

Abstract

AbstractIntroductionLittle is known about the impact of blood‐pool local impedance (LI) on lesion characteristics and the incidence of steam pops.MethodsRadiofrequency applications at a range of powers (30, 40, and 50 W), contact forces (CF) (5, 15, and 25 g), and durations (15, 30, 45, and 120 s) using perpendicular/parallel catheter orientation were performed in 40 excised porcine preparations, using a catheter capable of monitoring LI (StablePoint©, Boston Scientific). To simulate the variability in blood‐pool impedance, the saline‐pool LI was modulated by calibrating saline concentrations. Lesion characteristics were compared under three values of saline‐pool LI: 120, 160, and 200 Ω.ResultsOf 648 lesions created, steam pops occurred in 175 (27.0%). When power, CF, time, and catheter orientation were adjusted, ablation at a saline‐pool impedance of 160 or 200 Ω more than doubled the risk of steam pops compared with a saline‐pool impedance of 120 Ω (Odds ratio = 2.31; p = .0002). Lesions in a saline‐pool impedance of 120 Ω were significantly larger in surface area (50 [38–62], 45 [34–56], and 41 [34–60] mm2 for 120, 160, and 200 Ω, p < .05), but shallower in depth (4.0 [3–5], 4.4 [3.2–5.3], and 4.5 [3.8–5.5] mmfor 120, 160, and 200 Ω, respectively, p < .05) compared with the other two settings. The correlation between the absolute LI‐drop and lesion size weakened as the saline‐pool LI became higher (e.g., 120 Ω group (r2 = .30, r2 = .18, and r2 = .16, respectively for 120, 160, and 200 Ω), but the usage of %LI‐drop (= absolute LI‐drop/initial LI) instead of absolute LI‐drop may minimize this effect.ConclusionsIn an experimental model, baseline saline‐pool impedance significantly affects the lesion metrics and the risk of steam pops.