Acute-phase outcomes of very high-power short-duration radiofrequency ablation for typical atrial flutter: a substudy 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 even better safety profile compared to conventional parameters. While vHPSD has been extensively studied in pulmonary vein isolation, evidence in CTI ablation remains scarce. Purpose The FASD-HP trial is the first randomized controlled study to evaluate the non-inferiority of the efficacy and safety of vHPSD ablation in patients undergoing typical flutter ablation. Methods Prospective, multicenter, randomized (1:1), single-blind study. A total of 130 patients with typical atrial flutter were enrolled at two tertiary hospitals and randomized into two CTI ablation strategies: 66 patients were assigned to conventional ablation with 25–40 W applications of unlimited duration until achieving the minimum lesion parameter ("Ablation Index" >500 in the anterior and >400 in the posterior isthmus); 64 patients were assigned to the experimental treatment with point-by-point applications of 90 W for 4 seconds. Acute ablation success, reconnection site, complications, pain perception using the Visual Analogue Scale (VAS), and need for analgesia were analysed. Follow-up for the main trial extends to 12 months. Results The final bidirectional CTI block success rate was 98.4% in both groups. No differences were observed in the overall rate of reconnections. There were no significant differences in total procedure time. Both the total number of lesions and the number of lesions required to complete the first ablation line were significantly lower in the conventional ablation group (p = 0.001 and p < 0.001, respectively). The total RF time was significantly longer in the conventional ablation group (p < 0.001). No differences were observed in fluoroscopy time, radiation dose, or number of steam pops. Pain perception was significantly lower in the vHPSD group (mean VAS 4.12 ± 2.11 vs. 5.74 ± 2.35; p < 0.001), as was the need for additional fentanyl boluses (27.4% vs. 45.2%; p = 0.04). The rate of complications delaying hospital discharge was 3,22% in both groups. No cases of pericardial effusion, cardiac tamponade, or death were observed. Conclusions The FASD-HP study is the first clinical trial to prove that CTI ablation using the vHPSD strategy is non-inferior to the conventional approach in terms of acute efficacy and safety, while offering better patient tolerance. Long-term follow-up will determine whether these acute advantages translate into durable conduction block and reduced flutter recurrence.