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Objectives: This study sought to evaluate the efficacy and safety of using half-normal saline (HNS) as the cooling radiofrequency ablation (RFA) irrigant among patients who had failed prior, standard RFA., Background: Effective control of ventricular arrhythmias that arise from mid-myocardium may be refractory to standard RFA. Recent data suggest that delivering fluid with decreased ionic concentration during open-irrigated RFA can produce deeper RFA lesions., Methods: A 12-center prospective analysis was performed of all ablations using HNS for the treatment of ventricular arrhythmias (premature ventricular complex [PVC]/ventricular tachycardia [VT]) refractory to standard ablation with normal saline irrigant., Results: HNS RFA was used clinically to target 94 PVC/VTs refractory to standard ablation. Acute success was achieved in 78 of 94 (83%), with longer-term success occurring in 78 subjects after a mean follow-up of 6.1 ± 6.7 months (range, 3.0 to 25.2 months). Steam pops were observed among 12 (12.6%) patients. There were no significant changes in electrolytes measured before and after the use of HNS, and there were no complications related to HNS use., Conclusions: The use of HNS instead of normal saline irrigant during high-power delivery targeting deep myocardial substrate is safe and effective. PVC/VT sources previously unaffected by standard ablation may be successfully ablated with improved efficiency of radiofrequency delivery using HNS., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The goal of this study was to characterize differences in ablation lesions with varying radiofrequency ablation (RFA) power and time., Background: Increasing power delivery or prolonging duration can improve the efficacy of RFA. However, the extent to which ablation lesion characteristics change, based on varying degrees of power and duration, is unknown., Methods: An ex vivo model consisting of viable bovine myocardium in a circulating warmed saline bath was used. An open irrigated RFA catheter was positioned with 10 g of force in the perpendicular position, and RFA was delivered at powers of 20, 30, 40, and 50 W and for various time intervals, up to a total of 90 s, at each power. An in vivo porcine thigh preparation model was used to perform RFA at 50 W for 5 s and 20 W for 30 s. Lesion volumes were analyzed., Results: Greater power delivery and longer radiofrequency time increased ablation lesion size. However, compared with a proportional change in radiofrequency duration, the same proportional increase in power produced a significantly larger lesion volume (p < 0.01). For in vivo models, 50 W/5 s ablation lesions yielded similar volumes but significantly less depth than 20 W/30 s ablation lesions. Peak temperatures were not significantly different at 2 and 4 mm with 50 W/5 s versus 20 W/30 s., Conclusions: Varying power and duration will confer different ablation lesion characteristics that can be tailored according to the substrate/anatomy that is being ablated. This phenomenon has important implications during catheter ablation., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)