Cavo-tricuspid isthmus dependent flutter ablation using a focal monopolar pulsed-field ablation catheter

Radiofrequency catheter ablation of the cavo-tricuspid isthmus (CTI) has demonstrated excellent feasibility and a high success rate in obtaining bidirectional block (BIB). However, anatomical particularities (pouch, trabeculations and prominent ridge) can make the procedure challenging and increase the risk of thermal complications (steam pop). Conversely, the use of pulsed-field ablation (PFA) for CTI ablation has been associated with the presence of coronary spasm (CS) and conductive disorders (CD).

To assess the feasibility of CTI ablation using a focal monopolar PFA catheter (F-PFA), and to assess the risk of CS and CD.

We prospectively enrolled consecutive patients with CTI dependent flutter treated by a F-PFA system (Cardiofocus) through contact-force sensing catheters integrated in electroanatomical mapping systems. Intravenous nitroglycerine was administered prior to ablation. The ablation targeted mid CTI and a current of 25A was used for the caval part and 22A for the annular part of CTI. We evaluated feasibility (ablation time, number of ablation points needed, first pass block, bidirectional block) and safety (including occurrence of CS or CD). In cardiac CT-scans, we evaluated the course of the right coronary artery (RCA) and the distance to the hypothetical ablation zone. We marked the His position on the electro-anatomical mapping system and measured the distance between the ablation line and the His at the end of the procedure.

83 patients were included (18% female, mean age 66 years, CHA₂DS₂VA 1.6±1.3). Short procedure times 7 [5,11] and a high proportion of first pass block (93%) and further procedural data are presented in FIGURE 1. Regarding safety, 4 patients presented transient ST elevation and 2 patients showed a transient total AV block during ablation (FIGURE 2A). The patients with ST elevation were effectively treated with titrated IV nitroglycerin. 17 patients had preprocedural cardiac CT, including 1 patient with ST elevation. The distance between RCA and the target ablation zone was 18 [18,38] mm and was not significantly shorter in the patient presenting ST elevation (26mm, p=0.76) (FIGURE 2B). The patients with AV block had spontaneous resolution of their CD during the procedure. 17 patients had a His-CTI measurement, including 1 patient with AV block. The distance between His and the ablation zone was 37 [35,42] mm and was not significantly shorter in the patient with AV block (31mm, p=0.35) (FIGURE 2C).

CTI ablation using F-PFA is feasible. Transient CS and CD are rare and not solely related to the anatomical proximity of the CTI line to the His region and the RCA.

Procedure information and feasibility