How to enlarge lesion size in temperature control mode using an irrigation catheter with a flexible-tip of laser-cut kerfs

Abstract Background & Objectives The TactiFlex TM SE irrigation catheter installs a laser-cut flexible tip with a thermocouple embedded 0.3mm from the tip, being used with temperature-control mode. We aimed to elucidate a safer method to enlarge the lesion size using this catheter. Methods RF-applications were performed at a range of powers (35W, 40W, and 45W), CFs (10g/20g), and durations (60s, 120s, and 180s) using perpendicular/parallel catheter orientation with normal saline irrigation (NS-irrigation) and Half NS-irrigation (HNS-irrigation) in an ex-vivo model (Step 1). Further, similar RF-applications of 35W/40W/45W for 60s/120s/180 in NS-irrigation and 35W/40W for 60s/120s/180s in HNS-irrigation) were performed in 4 swine (Step 2). Lesion characteristics and the incidence of steam-pops were assessed. Results In this ex-vivo experiment, 47(16.3%) steam-pops (13 in NS-irrigation vs 34 in HNS-irrigation, p=0.001) were observed in 288 lesions. In NS-irrigation group, the most aggressive setting (45W/180s, n=7/13, 54%) played a large part of steam-pop occurrence. Lesion size proportionally increased with longer ablation duration, but not with HNS-irrigation. The optimal cut-off of %impedance-drop to predict steam-pops was 20% with the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 78.3%, 80.6%, 43.4%, and 95.1%, respectively. In the in-vivo experiment, steam-pops were not observed with NS-irrigation (n=0/35), but were with HNS-irrigation (6/21, 29%). Lesion size proportionally increased with longer ablation duration, but not with HNS-irrigation partially because of the higher incidence of temperature-guard use (p=0.07). The optimal cut-off of %impedance-drop to predict steam-pops was 24% with the sensitivity= 83.0%, specificity=52.0%, PPV= 17.2%, and NPV= 96.3%, respectively, but 20% may be used with a safety margin. Conclusions Although this novel catheter is generally safe, increasing ablation duration instead of using HNS-irrigation may be recommended for larger lesions.