Ambient circulation surrounding an ablation catheter tip affects ablation lesion characteristics

Abstract

Introduction The association between ambient circulating environments (CEs) and ablation lesions has been largely underexplored. Methods Viable bovine myocardium was placed in a saline bath in an ex vivo endocardial model. Radiofrequency (RF) ablation was performed using three different ablation catheters: 3.5 mm open irrigated (OI), 4, and 8 mm. Variable flow rates of surrounding bath fluids were applied to simulate standard flow, high flow, and no flow. For in vivo epicardial ablation, 24 rats underwent a single OI ablation and performed with circulating saline (30 ml/min; n = 12), versus those immersed in saline without circulation (n = 12). Results High flow reduced ablation lesion volumes for all three catheters. In no‐flow endocardial CE, both 4 mm and OI catheters produced smaller lesions compared with standard flow. However, the 8 mm catheter produced the largest lesions in a no‐flow CE. Ablation performed in an in vivo model with CE resulted in smaller lesions compared with ablation performed in a no‐flow environment. No statistically significant differences in steam pops were found among the groups. Conclusion A higher endocardial CE flow can decrease RF effectiveness. Cardiac tissue subjected to no endocardial CE flow may also limit RF for 4 mm catheters, but not for OI catheters; these findings may have implications for RF ablation safety and efficacy, especially in the epicardial space without circulating fluid or in the endocardium under varying flow conditions.

Radiofrequency energy floats, and heat sinks: The effects of convective cooling on lesion formation

“…4,5 Furthermore, intramyocardial perforators of coronary vessels may similarly influence ablation lesion geometry. 6 In this issue, Nussinovitch et al 7 Their result reflects and enforces the understanding that heat loss into the blood pool is an important factor that influences heat accumulation in the tissue. The linear flow at the catheter-tissue interface convectively replaces heated fluid with fluid of body temperature, establishing a steeper temperature differential that increases the rate of heat transfer from the tissue during ablation.…”

“…In this issue, Nussinovitch et al 7 investigated the effect of ambient normal saline flow (no flow, standard flow—5 L/min with source 100 mm from ablation site, and high flow—5 L/min with source 10 mm from ablation site) on lesion characteristics on using nonirrigated 4 mm (50 W, temperature‐gated 85°C), 8 mm (70 W, temperature‐gated 85°C) as well as 3.5 mm open‐irrigated (50 W power‐controlled) catheters in vitro, as well as the 3.5 mm open‐irrigated catheter (10 W for 60 s) in an‐open chest perfused rodent model with and without circulating saline. They show in‐vitro that high versus standard flow rates lead to smaller lesion dimensions and that standard flow versus no flow yielded bigger ablations for 4 mm but not 8 mm nonirrigated electrodes.…”