Background: CLOSE-guided atrial fibrillation (AF) ablation is based on contiguous (intertag distance ≤6 mm), optimized (Ablation Index >550 anteriorly and >400 posteriorly) point-by-point radiofrequency lesions. The optimal radiofrequency power remains unknown. Methods: The POWER-AF study is a prospective, randomized controlled monocentric study including patients with paroxysmal AF, planned for first CLOSE-guided pulmonary vein isolation using a contact force radiofrequency catheter (Thermocool SmartTouch, Biosense Webster, Inc, Irvine, CA). A total of 100 patients were randomized into 2 groups (1:1). The control group received AF ablation using the standard CLOSE protocol (35 W), whereas in the experimental group, pulmonary vein isolation was performed using high power (45 W). Endoscopic evaluation was performed in patients with intraesophageal temperature rise >38.5 °C. Results: The resulting sample size was 96 (48+48) patients. In the high power group, shorter procedure time (80 versus 102 minutes, P <0.001), shorter total radiofrequency application time (16 versus 26 minutes, P <0.001), and radiofrequency time per application (26 versus 37 s anteriorly, P <0.001 and 13 versus 17 s posteriorly, P <0.001) were observed. Endoscopic evaluation (performed in 19/48 versus 25/48 patients respectively, P =0.31) showed an ulcerative perforation in a high power group patient (treated by endoscopic stenting and normalization after ≈4 months) and a superficial ulcerative lesion in a control group patient (conservative treatment). Both occurred following excessive Ablation Index applications (up to 460 and 480, respectively) with excessive contact force (30 g on average, with peaks up to 50 g). Six-months AF recurrence was not significantly different (10% in high power versus 8% in control, P =0.74). Conclusions: This randomized controlled study shows that a 45 W radiofrequency power CLOSE protocol in patients with paroxysmal AF significantly increases the global procedural efficiency with similar midterm efficacy. However, our study showed a narrower safety margin and a limited increased efficiency at the posterior wall using high power. This advocates against the use of high power in the region neighboring the esophagus.

Aims: "CLOSE"-guided pulmonary vein isolation (PVI) is based on contiguous (≤6 mm) and optimized radiofrequency (RF) ablation lesions (ablation index[AI] ≥ 400 posteriorly and ≥ 550 anteriorly]. However, the optimal RF power to reach the desired AI is unknown. Therefore we evaluated the efficiency of an ablation strategy using higher power (40 W) during a first "CLOSE"-guided PVI.Methods: Eighty consecutive patients undergoing "CLOSE"-guided PVI for symptomatic paroxysmal atrial fibrillation were ablated with 40 W (group A). Results were compared with 105 consecutive patients enrolled in the "CLOSE to CURE"-study and were ablated using the same protocol with 35 W (group B). Results:In group A, ablation was associated with shorter ablation procedure time (91 vs 111 minutes; P < .001), shorter fluoroscopy time (5 vs 11 minutes; P < .001), shorter PVI time (48 vs 64 minutes; P < .001), shorter RF time (20 vs 28 minutes; P < .001), lower RF time per application (22 vs 29 seconds; P < .001), less RF applications (52 vs 58; P < .001), and less catheter dislocations (1 vs 2; P = .002). The impedance drop (12 vs 13 Ω; P = .192), first-pass isolation rate (99% vs 93%; P = .141) and acute reconnection rate (6% vs 4%; P > .733) were similar in both groups (groups A and B, respectively). No complications occurred. In group A, a gastroscopy-performed in five patients with esophageal temperature rise more than 42°C-did not reveal any esophageal lesion. Postprocedural recurrence of atrial tachyarrhythmia at 1 year was not significantly different between both groups.Conclusions: Using the "CLOSE"-protocol, increased power increases the efficiency of PVI without compromising patients' safety. K E Y W O R D S atrial fibrillation, contact force, high power ablation, pulmonary vein isolation Maria Kyriakopoulou and Jean-Yves Wielandts contributed equally to this study. a Adenosine test performed in 97 out of 105 patients. F I G U R E 1 Two representative examples of "CLOSE"-guided encirclement of the pulmonary veins (PV) and the radiofrequency parameters (median/median value) of all VISITAG points in one patient from group A (40 W; A) and one patient from group B (35 W; B). Posteroanterior view. Red VISITAG points with ablation index (AI) > 550 and pink VISITAG points with AI > 400. Asterisk (*) on two dislocation points in group B (35 W) 1094 | KYRIAKOPOULOU ET AL.

The HGP is an efficient way to manage walk-in patients with regard to process time and utilization of additional diagnostic resources. The involvement of GPs in the HGPs should be considered as a promising model to overcome the inappropriate use of resources in EDs for walk-in patients who can be treated by ambulatory care.

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