Very high-power short-duration radiofrequency ablation in patients with typical atrial flutter: rationale and design of the FASD-HP randomized trial

Background: The aim of cavotricuspid isthmus (CTI)-dependent flutter ablation is the bidirectional conduction block of the CTI. Very-high-power short-duration (vHPSD) radiofrequency ablation aims to minimize conductive heating and increase resistive heating to create shallower but wider lesions in a very short time, while reducing the risk of collateral tissue damage. Experimental studies have shown that it produces effective transmural lesions with an equal or better safety profile compared to conventional parameters. There are published and ongoing trials studying long-term outcomes of this technique for pulmonary vein isolation, but there is a lack of evidence regarding its use in flutter ablation.

Methods and results: Multicenter 1:1 randomized, single-blind study. Two CTI ablation strategies are compared: (1) conventional treatment arm consisting of 25-40-W applications of unlimited duration until reaching the minimum value of one of the currently accepted lesion markers (Ablation Index > 500 at the anterior half of the CTI and > 400 at the posterior half with CARTO3 system); (2) experimental treatment arm consisting of CTI block using point-by-point applications of very-high-power (90 W) short duration (4 s). The primary objective is to evaluate the non-inferiority of the efficacy and safety of vHPSD ablation in patients undergoing typical flutter ablation. Secondary objectives include comparison of total radiofrequency time, number of applications, number of steam pops, percentage of reconnections, procedure duration, pain during the procedure, and time to flutter recurrence.

Conclusions: The FASD-HP trial is the first clinical trial to investigate the non-inferiority of CTI ablation with vHPSD in patients with typical atrial flutter.

Clinical trial registration number: The study was registered at http://www.

Clinicaltrials: gov (NCT05777850) on March 21, 2023.