AUTHOR=Qu Lijuan , Guo Min , Sun Meng , Wang Rui , Zhang Nan , Li Xin 

TITLE=Effect of Baseline Impedance in Radiofrequency Delivery on Lesion Characteristics and the Relationship Between Impedance and Steam Pops

JOURNAL=Frontiers in Cardiovascular Medicine

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2022.872961

DOI=10.3389/fcvm.2022.872961

ISSN=2297-055X

ABSTRACT=Objective: To explore the effects of baseline impedance (R) and power (P) on radiofrequency ablation lesion characteristics and their correlation with steam pops  through using ThermoCool SmartTouch‐SF (STSF) catheters in the porcine heart.
Method: A porcine left ventricle was submerged in 37°C saline ex vivo, and the experiment was performed with various P (P = 30, 40, 50, and 60 W) and multiple R loads (R = 80–100, 100–140, 140–180, and 180–220 Ω) to reach the target ablation index (AI; AI = 350, 450, and 500) or reach the target ablation time using a fixed contact force (CF; CF = 10–15 g) and the same saline irrigation (30 W / 8 ml/min or 40–60 W / 15 ml/min), repeated five times under each condition. 
Results: The surface diameter, maximum diameter, depth, and volume of the lesions were strongly correlated with the AI (P = 40 W, R = 100–140 Ω, CF = 10–15 g) (r = 0.5412; r = 0.7889; r = 0.9366; and r = 0.913, respectively; all p < 0.05). As the R increased, the maximum diameter, depth, and volume of the lesions significantly increased (AI = 350, P = 30 W). Moreover, the higher the baseline R was, the greater the absolute value of the R decrease (r = 0.9035, p < 0.05, Y = 0.2759 × X − 18.33) was observed. Under high power and high impedance, the occurrence rate of steam pop was high (P = 60 W, R = 180–220 Ω, AI when steam pop occurred: 480 ± 26.5, ablation time: 11.29 ± 1.04 s).
Conclusion: Radiofrequency catheter ablation in power-controlled mode resulted in various lesion characteristics that were related to diverse baseline Rs. In addition, the incidence of steam pops was strongly correlated with high baseline R and high P.