Background: Traditional management of atrial flutter (AFl) includes catheter ablation and pharmacological therapy. Antitachycardia pacing (ATP) has been explored as an alternative, with variable efficacy in terminating atrial arrhythmias. The intrinsic ATP (iATP) algorithm, previously validated for ventricular tachycardia, may offer enhanced efficacy in the atrium by leveraging programmed stimulation (PS). Objective: This study evaluates the efficacy of iATP in terminating AFl and compares it to traditional ramp pacing protocols. Methods: A prospective, randomized crossover trial was conducted in patients undergoing AFl ablation. Three ATP protocols were tested: (1) ramp pacing at 91% of tachycardia cycle length (TCL), (2) ramp pacing at 81% TCL, and (3) iATP, which incorporated PS with decrementing extra-stimuli. The primary endpoint was termination of AFl or acceleration to atrial fibrillation (AF), which was considered beneficial for rate control. Results: Seventeen patients completed the protocol. AFl termination rates were 17.6% (Protocol 1), 20.5% (Protocol 2), and 38% (iATP). The iATP protocol also induced AF in 8 cases, compared to 1 and 4 cases in Protocols 1 and 2, respectively. The increased efficacy of iATP is attributed to its ability to introduce premature wavefronts into the excitable gap, enhancing termination rates. Conclusion: iATP demonstrated superior efficacy in terminating AFl and accelerating it to AF compared to traditional ramp pacing. These findings support further exploration of iATP as a pacing-based intervention in atrial arrhythmia management. Future studies should assess its broader applicability in atypical AFl and AF.

Introduction: During pulmonary vein isolation (PVI) of atrial fibrillation (AF), electroanatomic mapping (EAM) is used to characterize voltage characteristics of the left atrium, identifying low voltage areas (LVA) as ≤0.5 mV. Posterior wall (PW) LVAs have been used as ablative targets in patients with persistent AF, showing mixed results. Methods and Results: We compared the mapping performance and PW LVA characterization between the novel 8-spline high-resolution Octaray catheter versus the 5-spline Pentaray catheter. An analysis of registry patients from ALPINE (Adjunctive Left atrial Posterior Isolation Efficacy Study), a single-center, prospective, randomized control trial evaluating outcomes in index PVI +/- PW isolation in patients with >10% PW LVA, was performed. EAMs of initial registry patients were performed with Pentaray (January – May 2022) and were compared with later EAMs mapped with Octaray (May 2022 – August 2023) to determine differences in procedural metrics and PW LVA characterization. EAMs of 273 patients (87 with Pentaray, 186 with Octaray) were analyzed. There were no differences in baseline characteristics. Mapping with Octaray resulted in increased mean normal PW voltage (97.05% vs 93.78%; p=0.002), and less mean PW LVA (2.64% vs 4.36%; p<0.01) than Pentaray. Octaray resulted in significantly lower mapping time (13 vs 16 minutes; p<0.01) and greater number of Fast Anatomic Mapping (FAM) points collected (8081 vs 2939; p<0.001). When adjusted for baseline confounders, a multivariable linear regression analysis revealed that use of Octaray did have an independent, significant association corroborating these findings. Conclusion: To our knowledge, our study contains one of the largest groups of patients with increased normal PW voltage, and less PW LVA, when using Octaray compared to Pentaray. It is possible the higher density mapping capability of the Octaray leads to more mapped points, improved contact, and less voltage interpolation than prior catheter technology, with resultant decreases in LVA characterization. The mapping catheter’s role in quantifying LVA is significant due to its treatment implications with respect to pursuing adjunct PW modification in AF ablation. Further investigation of the mapping performance, voltage characteristics, and procedural outcomes of the Octaray would be beneficial.

Abstract Background: Pulmonary vein (PV) reconnection and the onset of non-PV triggers is frequently the cause of atrial fibrillation (AF) recurrence after radiofrequency catheter ablation (RFCA). The effectiveness of using isoproterenol for unmasking dormant conduction and non-PV-triggers during AF RFCA and its effect on improving procedural and clinical outcomes is still controversial. Objective: To evaluate the effectiveness of isoproterenol for unmasking dormant conduction and non-PV-triggers during RFCA for paroxysmal AF (PAF) and its effects on procedural and long-term clinical outcomes. Methods: In this prospective multicenter cohort from the REAL-AF registry, patients who underwent RFCA for PAF with and without isoproterenol administration from January 2018 to May 2023 were included. The primary efficacy outcome was freedom from all-atrial arrhythmias at 12-month follow-up. Secondary outcomes included procedural and long-term clinical outcomes, and procedure-related complications. Results: A total of 1102 patients were included (isoproterenol=325 vs. control=777) (mean age 66.73±10.19 years; 53.05% male). There were no differences in baseline characteristics between the groups. Dormant conduction/non-PV triggers with isoproterenol was observed in 10.2% of the patients. Isoproterenol administration was associated with increased procedural times (109 (83-137.5) vs. 96 (74-122), p=0.002), and decreased rates of first-pass PV isolation (74.84% vs. 80.14%, p=0.007). There were no differences in freedom from all-atrial arrhythmias (HR 0.87, 95% CI [0.61-1.24], p=0.4) or long-term clinical outcomes at 12 months of follow-up between the groups. Conclusion: In patients undergoing RFCA for PAF, the use of isoproterenol was associated with increased procedural times and more extensive ablation, without improved clinical outcomes at 12-month follow-up.

Background: High-frequency low-tidal-volume (HFLTV) ventilation is a safe and cost-effective strategy that improves catheter stability, first-pass pulmonary vein isolation, and freedom from all-atrial arrhythmias during radiofrequency catheter ablation (RFCA) of paroxysmal and persistent atrial fibrillation (AF). However, the incremental value of adding rapid-atrial pacing (RAP) to HFLTV-ventilation has not yet been determined. Objective: To evaluate the effect of HFLTV-ventilation plus RAP during RFCA of paroxysmal AF on procedural and long-term clinical outcomes compared to HFLTV-ventilation alone. Methods: Patients from the REAL-AF prospective multicenter registry, who underwent RFCA of paroxysmal AF using either HFLTV+RAP (500-600 msec) or HFLTV ventilation alone from April 2020 to February 2023 were included. The primary outcome was freedom from all-atrial arrhythmias at 12-month follow-up. Secondary outcomes included procedural characteristics, long-term clinical outcomes, and procedure-related complications. Results: A total of 545 patients were included in the analysis (HFLTV+RAP=327 vs. HFLTV=218). There were no significant differences in baseline characteristics between the groups. No differences were observed in procedural (HFLTV+RAP 74 [57-98] vs. HFLTV 66 [53-85.75] min, p=0.617) and RF (HFLTV+RAP 15.15 [11.22-21.22] vs. HFLTV 13.99 [11.04-17.13] min, p=0.620) times. Both groups showed a similar freedom from all-atrial arrhythmias at 12-month follow-up (HFLTV+RAP 82.68% vs. HFLTV 86.52%, HR=1.43, 95% CI [0.94-2.16], p=0.093). There were no significant differences in freedom from AF-related symptoms (HFLTV+RAP 91.4% vs. HFLTV 93.1%, p=0.476) or AF-related hospitalizations (HFLTV+RAP 98.5% vs. HFLTV 97.2%, p=0.320). Procedure-related complications were low in both groups (HFLTV+RAP 0.6% vs. HFLTV 0%, p=0.247). Conclusion: In patients undergoing RFCA for paroxysmal AF, adding RAP to HFLTV-ventilation was not associated with improved procedural and long-term clinical outcomes.