This randomized study aims to compare the left atrial (LA) lesion size, function, and tissue damage following pulmonary vein isolation (PVI) by high-power short-duration (HPSD) radiofrequency (RF) and second-generation cryoballoon (CB2) ablation. We enrolled 40 patients with paroxysmal atrial fibrillation who underwent PVI by HPSD RF (n = 21) or CB2 (n = 19). Every patient underwent LA CT angiography and transthoracic echocardiography (TTE) to assess the LA anatomy and function. Biomarker levels (hs-cTnT, hs-CRP, LDH) were compared pre- and post-procedurally. Pre- and post-ablation high-density mapping (HDM) was performed. The isolation area was defined under 0.2 mV bipolar voltage (low voltage area, LVA). We calculated the post-PVI LVA/LA surface ratio using LA CT-HDM merge images. At 3-month follow-up, TTE was performed to assess the changes in LA function. Post-ablation hs-cTnT level was significantly higher in the RF group (RF: 1249 ± 469 ng/L, CB2: 995 ± 280 ng/L, p = 0.024). Post-PVI hs-CRP (RF: 9.53 ± 10.30 mg/L, CB2: 12.36 ± 5.76 mg/L, p = 0.034) and LDH levels (RF: 349.9 ± 65.6 U/L, CB2: 451.6 ± 91.3 U/L, p < 0.001) were significantly higher following CB2 ablation. Post-PVI LVA/LA surface ratios were 8.37 ± 6.42% in the RF group and 13.58 ± 8.92% in the CB2 group (p = 0.022). LA function did not change significantly after the PVI procedure. Our data indicate that second-generation cryoballoon ablation produces a significantly larger LA lesion size compared to “point-by-point” HPSD radiofrequency. Both techniques preserve LA function. The myocardial component of tissue loss appears to be higher using HPSD radiofrequency ablation, with less collateral damage.

Funding Acknowledgements Type of funding sources: None. Introduction In recent times, high-power short-duration (HPSD) radiofrequency ablation (RFA) has emerged as an alternative strategy for pulmonary vein isolation (PVI) in atrial fibrillation (AF). Purpose We aimed to compare HPSD approach and conventional, ablation-index (AI) guided PVI using contact force sensing ablation catheters in respect of efficacy, safety, procedural characteristics, and outcome. Methods A total of 184 consecutive AF patients with first PVI were enrolled (age: 60 ± 11 years, paroxysmal: 56.5%, persistent: 43.5%) between November 2016 and December 2019. An ablation protocol of 50W energy with 15-20 g contact force was used for a duration of 8-12 sec based on the loss of capture concept in the HPSD group (n = 91) meanwhile, PVI was achieved according to the conventional power settings (posterior wall 25W, AI: 400, anterior wall 35W, AI: 550 ) in the control group (n = 93). During 1-year follow-up, documented AF for more than 30 seconds was considered as recurrence. Results Radiofrequency time and procedural time were significantly shorter using HPSD ablation (26.0 ± 12.7 min vs. 42.9 ± 12.6 min, p &lt; 0.001, and 91 ± 30.1 min vs. 105.3 ± 28 min, p &lt; 0.001). The HPSD strategy significantly lowered fluoroscopy time and radiation dose (5.47 ± 4.07 min vs. 8.15 ± 10.04 min, p = 0.019, and 430.2 ± 534.06 cGycm2 vs. 604.2 ± 633.9 cGycm2, p = 0.046). The HPSD group showed significantly less arrhythmia recurrence during 1-year follow-up with 76.9% of patients free from AF compared to 66.7% in the control group (p = 0.037). No pericardial tamponade, periprocedural thromboembolic complication, or atrio-oesophageal fistula occurred in the HPSD group. We observed 2 pericardial tamponade and 1 periprocedural stroke in the control group. Conclusions HPSD RFA for AF was demonstrated to be safe, and lead to significantly improved 1-year outcome in our mixed patient population. HPSD protocol significantly shortened procedural and radiofrequency time with decreased fluoroscopy time and radiation exposure.

Funding Acknowledgements Type of funding sources: None. Background Subcutaneous ICD (S-ICD) is an established therapy for prevention of sudden cardiac death due to ventricular arrhythmias (VA). One major drawback of the S-ICD is the lack of antibradycardia pacing. Theroretically the S-ICD can be used in combination with endocardial or epicardial pacemaker (PM), or even cardiac resinchronization (CRT) devices, but recently there are only few case reports available on this topic. Purpose To evaluate the feasibility and safety of concomitant use of endocardial or epicardial PM or CRT devices and S-ICD in a single center patient cohort. Methods Fifty-seven patients underwent S-ICD implantation in our center between 2017 and 2022. Based on individualized decision making-process, six out of these patients underwent the S-ICD implantation without explantation of previuosly implanted transvenous devices, or after epicardial PM or CRT implantation (group 1). The procedural and follow-up data of these patients were compared with data of the other 51 patients (group 2). All patients underwent successful S-ICD screening before implantation. Patients with previously implanted devices were screened either in bipolar pacing mode and either during intrinsic rhythm, if present. S-ICD implantations were performed under general anaesthesia (33 %) or under deep sedation with ultrasound guided regional nerve blocks (66 %) using intermuscular generator placement and two incision technique. Defibrillation threshold test was performed successfully in all the 57 patients. Results All S-ICD implantations were performed successfully without any procedural complications. There were no significant difference between group 1 and group 2 in terms of age (52,3±20 yrs vs. 37,7±18,5 yrs, p=0,75), ejection fraction (49,2±25,6 % vs. 46,5±21 %, p=0,77), procedure duration (57±9,7 min. vs. 52,2±15,5 min., p=0,46), and the mean follow-up duration (20,5±23,6 months vs. 25±18,8 months, p=0,59). During follow-up, one patient in group 1 (17%), and 10 patients in group 2 (19,6 %) experienced adequate ICD therapies due to VA. There were no inadequate ICD therapy in group 1, but eight patients (15,6 %) in group 2 suffered from inadequate ICD shocks caused by T wave oversensing (3/8), atrial fibrillation (2/8) myopotential oversensing (2/8,) and S-ICD lead fracture (1/8). In group 1, no interferences occured between the implanted devices, and no missed S-ICD therapy were observed during induced or spontaeous VA due to pacing artefact oversensing by the S-ICD caused by undersensing of the VA by the pacemakers. Non of the patients in group 2 experienced symptomatic bradycardia required antibradycardia pacing during follow up. Conclusion Based on our observations, S-ICD implantation after previously implanted endocardial or epicardial pacemaker or CRT systems seems feasible and safe. After individualized decision-making, with careful screening and device programming the potential interference between the implanted devices can be prevented.

Funding Acknowledgements Type of funding sources: None. Introduction Electrical storm (ES) is a life-threatening clinical condition characterized by the recurrence of three or more episodes of ventricular tachycardia (VT) and/or ventricular fibrillation within 24 hours, leading to ICD therapy. Catheter ablation of VT in patients with ES is a high-risk procedure but has been shown to reduce VT recurrence and the number of appropriate ICD therapies in patients with structural heart disease. Purpose Our study aimed to compare the characteristics and outcomes of VT ablation in patients with or without ES. Methods Our single-center study included a cohort of 39 consecutive patients (31 men, mean age=60.9±18.4 years) who underwent VT ablation between January 2020 and January 2022, 21 of them (53.8%) due to ES and 18 patients (46.2%) had an elective procedure. Clinical and procedural characteristics, VT recurrence, and mortality rates were compared between the two groups. Results Patients with ES were older than patients without ES (67.8 vs 54.2 years, p=0.004), they were mainly presented with ischaemic cardiomyopathy (85.7% vs 27.8%, p&lt;0.0001), had a higher prevalence of congestive heart failure (90.5% vs 44.4%, p=0.001) and a more severe left ventricular dysfunction (LVEF: 30.8% vs 46.9%, p=0.002). During the procedure, in the ES group, all of the patients had left-sided ablation (transaortic: 80.9%, transseptal: 19.1%), while in patients without ES, 72.2% of the procedures were left-sided (p=0.04). In 8/39 patients (20.5%) endo-epicardial access was needed. The number of RF ablation points was significantly higher in the ES group (64.1 vs 36.1 points, p=0.01). Complications were detected only in the ES group: intraprocedural death occurred in one case due to an ES and consequently cardiogenic shock, and one patient had a dissection of the right femoral artery. There was no significant difference regarding procedure time, fluoroscopy time, and radiation exposure. The in-hospital 30-day mortality was 8/21 (28.6%) in patients with ES, while no patients died in the non-ES group. During longer clinical follow-up, there was no significant difference in the recurrence of VT episodes and mortality. Conclusion Patients presented with ES are a more vulnerable population with many comorbidities. Catheter ablation of VT in patients with ES is a more complex procedure with a higher complication rate and these patients have a higher risk of in-hospital mortality. Further studies are needed to determine the optimal timing of VT ablation in this patient population.