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Background/Introduction The novel catheter with 6 thermocouples for real-time temperature monitoring during irrigated radiofrequency ablation was designed to potentially enhance safety and effectiveness of the Smart Touch Surround Flow (STSF) catheter by incorporating real-time temperature sensing. A supplementary, novel algorithm was developed to modulate power to maintain target temperature during high power/short duration ablation (90W, 4s). Purpose This sub-analysis was performed to examine consistency and reproducibility of the procedural efficiencies and acute success of the novel catheter with optimized temperature control and microelectrodes in treating paroxysmal atrial fibrillation (PAF) across multiple sites from two initial feasibility studies, in standard (QMODE) and high power/short duration (QMODE+) temperature-control ablation modes. Methods The QDOT-MICRO (QMODE, NCT02944968; N=42) and QDOT-FAST (QMODE+, NCT03459196; N=52) studies were both prospective, non-randomized multi-center, clinical investigations completed across 6 and 7 centers, respectively, in Europe. Procedural efficiencies and acute success (PVI via entrance block) was examined across sites within the study. Results In the QDOT-MICRO study, median procedure time (105–155 min), RF ablation time (27.7–39.5 min), and fluoroscopy times (2.2–8 min) during QMODE ablation were similar across the 6 sites. In QMODE+ ablation, median procedure time, RF ablation time, and fluoroscopy times all fall within (84–134 min), (4.8–9.7 min) and (1.1–9.6 min), respectively, across the 7 sites. Fluid delivery by the study catheter was low in both studies: QDOT-MICRO 547±278mL (mean ± SD); QDOT-FAST 382±299. mL (mean ± SD); which is 39.1 and 57.4% lower, respectively, than reported in the SMART SF trial. Esophageal temperature probe was used in the majority of patients (30/42 for QDOT MICRO and 51/52 for QDOT-FAST). Acute PVI was successful in 100% of patients in both studies with no deaths or unanticipated AEs. Conclusion(s) In both feasibility studies, procedural efficiencies were reproducible across study sites in both QMODE and QMODE+, with 100% acute success and good safety outcomes. Efficiencies are likely to improve with further experience. These results need to be confirmed in larger trials. Acknowledgement/Funding Both Studies are Company Sponsored Studies funded by Biosense Webster, Inc.

Introduction Cavo tricuspid isthmus ablation (CTIA) is an effective first-line treatment for typical atrial flutter (AFL). However, many patients develop atrial fibrillation (AF) after successful CTIA. Knowledge about recurrent arrhythmia after CTIA mainly comes from small cohort studies with limited follow-up. Purpose To describe incidences of AFL re-ablation and AF-ablation after first-time CTIA in a nation-wide cohort. Method In the Danish National Ablation Registry we identified patients undergoing first-time CTIA during 2010–2016. Subsequent CTIA and AF-ablation procedures were identified until March 1st, 2018. We gathered information on patient comorbidities in the Danish National Patient Registry. Results We identified 2409 patients undergoing first-time CTIA. Median age was 66 (IQR 58–72) years, and 1952 (81%) were men. 78 (3%) had a history of AF. Acute procedural succes was achieved in 2288 (95%) patients. During mean follow-up of 4±1.7 years, 242 (10%) patients underwent CTI re-ablation and 326 (13.5%) ablation for AF. Baseline characteristics associated with CTI re-ablation included prolonged procedural time, unsuccessful first CTIA, age Predictive characteristics Characteristics associated with CTI re-ablation HR 95% CI p-value Procedural time 1.003 (1.001–1.006) 0.01 Unsuccesful first CTIA procedure 3.42 (2.10–5.55) Conclusion In a nation-wide cohort undergoing CTIA for AFL, 10% of patients underwent CTI re-ablation and 13.5% were ablated for AF during mean follow-up of 4±1.7 years. Probability of undergoing a second ablation procedure was higher in younger patients with less comorbidity.