Radiofrequency (RF) lesion metrics are influenced by underlying parameters like RF power, duration and contact force (CF), and utilization of lesion metric indices (Ablation Index, AI) is a proposed strategy to predict lesion quality. The aim of this study was to analyze the influence of underlying parameters on lesion metrics of high power short duration (HPSD) and standard RF applications using an in-silico and ex-vivo model.
Methods
An in-silico simulation study was designed to simulate HPSD and standard ablations, in which ablation parameters could systematically be varied. For each simulated ablation process (n=5732), the corresponding AI value was calculated. HPSD and standard RF settings were then applied in a porcine ex-vivo model (n=120 lesions). The ex vivo model consisted of a saline-filled container including a thermostat, a circulating pump, an indifferent electrode, and porcine thigh muscle preparations. A SmartTouch SF ablation catheter (Biosense Webster, Diamond Bar, USA) was stabilized in a steerable sheath (Agilis, Abbott, Chicago, USA) that was mounted on a tripod. A digital precision caliper was used to measure the geometry of each ex-vivo ablation lesion (surface diameter, maximum depth, maximum diameter, depth at maximum diameter) and the resulting ablation lesion volume was calculated and lesions were analyzed regarding underlying parameters.
Results
RF applications of 50W/13s, 60W/10s, 70W/7s, and 80W/6s resulted in lesion volumes not significantly different from standard RF applications (30W/30s, p>0.05). HPSD lesion diameters were significantly larger and lesion depths were significantly smaller (p<0.01) when compared to standard settings. Prolonging RF duration from 5s to 10s resulted in a +27.5% increase, whereas a prolongation of RF duration from 35s to 40s resulted in a +4.8% increase of AI value only. An increase of CF from 1g to 10g resulted in a +73.0%, an increase of CF from 20g to 30g resulted in a +10.1% increase of AI value. Different ablations settings and their resulting AI values are quantitatively compared in Figure 1.
Lesion geometry characteristics of standard and HPSD RF applications are summarized in Figure 2. There was no significant difference in total lesion volumes between standard RF and HPSD applications (p=0.46). HPSD applications resulted in significantly different lesion geometries when compared to standard applications: HPSD lesion depth was significantly smaller (p<0.01), and lesion maximum diameter was significantly larger (p<0.01) with increasing RF power and shortening RF duration.
Conclusions
High power short duration RF applications resulted in similar lesion volumes when compared to standard RF application, but with different lesion geometry, showing a larger maximum diameter and a smaller lesion depth.
A x-fold increase of RF power resulted in a larger lesion size increase than a x-fold increase of RF duration. In all RF settings, the fastest increase of lesion size was observed during the first 10 seconds of RF application. While achieving contact forces of 10g to 20g had remarkable effects on resulting lesion size, contact forces exceeding 30g showed a disproportional lower effect.
https://www.abstractserver.com/dgk2019/jt/abstracts//V486.htm