Background - Irreversible electroporation (IRE) is a promising new non-thermal ablation technology for pulmonary vein (PV) isolation in patients with atrial fibrillation (AF). Experimental data suggest that IRE ablation produces large enough lesions without the risk of PV stenosis, artery, nerve or esophageal damage. This study aimed to investigate the feasibility and safety of single pulse IRE PV isolation in patients with AF. Methods - Ten patients with symptomatic paroxysmal or persistent AF underwent single pulse IRE PV isolation under general anesthesia. Three-dimensional reconstruction and electroanatomical voltage mapping (EnSite Precision TM , Abbott) of left atrium and PVs were performed using a conventional circular mapping catheter. PV isolation was performed by delivering non-arcing, non-barotraumatic 6 ms, 200 J direct current IRE applications via a custom non-deflectable 14-polar circular IRE ablation catheter with a variable hoop diameter (16-27 mm). A deflectable sheath (Agilis TM , Abbott) was used to maneuver the ablation catheter. A minimum of two IRE applications with slightly different catheter positions were delivered per vein to achieve circular tissue contact, even if PV potentials were abolished after the first application. Bidirectional PV isolation was confirmed with the circular mapping catheter and a post ablation voltage map. After a 30-minute waiting period, adenosine testing (30 mg) was used to reveal dormant PV conduction. Results - All 40 PVs could be successfully isolated with a mean of 2.4±0.4 IRE applications per PV. Mean delivered peak voltage and peak current were 2154 ± 59 V and 33.9 ± 1.6 A, respectively. No PV reconnections occurred during the waiting period and adenosine testing. No periprocedural complications were observed. Conclusions - In the 10 patients of this first-in-human study, acute bidirectional electrical PV isolation could be achieved safely by single pulse IRE ablation.

Purpose: High-intensity focused ultrasound (HIFU) is a potential noninvasive thermal ablation method for the treatment of peripheral artery disease. Dual-mode ultrasound arrays (DMUA) offer the possibility of simultaneous imaging and treatment. In this study, safety and feasibility of femoral artery robotassisted HIFU/DMUA therapy was assessed. Methods: In 18 pigs ($50kg), angiography and diagnostic ultrasound were used to visualize diameter and blood flow of the external femoral arteries (EFA). HIFU/DMUA-therapy was unilaterally applied to the EFA dorsal wall using a 3.5 MHz, 64-element transducer, closed-loop-control was used to automatically adjust energy delivery to control thermal lesion formation. A continuous lesion of at least 25 mm was created by delivering 6-8 HIFU shots per imaging plane perpendicular to the artery spaced 1 mm apart. Directly after HIFU/DMUA-therapy and after 0, 3 or 14 days follow up, diameter and blood flow were measured and the skin was macroscopically examined for thermal damage. The tissue was removed for histological analysis. Results: No complications were observed. The most frequently observed treatment effect was formation of scar tissue, predominantly in the adventitia and the surrounding tissue. No damage to the endothelium or excessive damage of the surrounding tissue was observed. There was no significant decrease in the mean arterial diameter after HIFU/DMUA-therapy. Conclusion: HIFU/DMUA therapy successfully targeted the vessel walls of healthy porcine arteries, without causing endothelial damage or other vascular complications. Therefore, this therapy can be safely applied to healthy arterial walls in animals. Future studies should focus on safety and dose-finding in atherosclerotic diseased arteries.

Introduction Recent studies demonstrated that irreversible electroporation (IRE) ablation may be an alternative method for thermal ablation for pulmonary vein isolation. Development of gaseous microemboli during catheter ablation might lead to asymptomatic ischemic events and is therefore an important research topic. Gas formation during arcing with direct current catheter ablation has been studied in the past, however not for nonarcing IRE‐ablation. Objective The aim of the present study was to visualize, quantify, and characterize gas formation during nonarcing millisecond IRE‐pulses using a multielectrode circular catheter. Methods In vitro, gas formation during IRE‐pulses was studied using a high‐speed imaging, direct volume measurements, and a bubble counter. Gas formation was compared between cathodal and anodal IRE‐pulses and between a small and large catheter hoop diameter. Results High‐speed images showed the location and dynamics of gas formation during cathodal and anodal millisecond IRE‐pulses. The direct volume measurements demonstrated a significantly larger volume for cathodal than for anodal IRE‐pulses (P < .001), and no significant difference between small and large hoop diameters. A strong linear relationship was found between delivered charge and total gas volume (r = 0.99). Bubble counter measurements showed that cathodal IRE‐pulses produced more and larger gas bubbles than anodal IRE‐pulses. The ratio of total gas volume between cathodal and anodal IRE‐pulses is different as predicted from electrolysis theory. Conclusion In vitro, millisecond anodal IRE‐pulses produce significantly less and smaller gas bubbles than millisecond cathodal IRE‐pulses. In vivo experiments are required to investigate the clinical implication of these observations.

Aims  Irreversible electroporation (IRE) ablation is a non-thermal ablation method based on the application of direct current between a multi-electrode catheter and skin electrode. The delivery of current through blood leads to electrolysis. Some studies suggest that gaseous (micro)emboli might be associated with myocardial damage and/or (a)symptomatic cerebral ischaemic events. The aim of this study was to compare the amount of gas generated during IRE ablation and during radiofrequency (RF) ablation. Methods and results In six 60–75 kg pigs, an extracorporeal femoral shunt was outfitted with a bubble-counter to detect the size and total volume of gas bubbles. Anodal and cathodal 200 J IRE applications were delivered in the left atrium (LA) using a 14-electrode circular catheter. The 30 and 60 s 40 W RF point-by-point ablations were performed. Using transoesophageal echocardiography (TOE), gas formation was visualized. Average gas volumes were 0.6 ± 0.6 and 56.9 ± 19.1 μL (P &lt; 0.01) for each anodal and cathodal IRE application, respectively. Also, qualitative TOE imaging showed significantly less LA bubble contrast with anodal than with cathodal applications. Radiofrequency ablations produced 1.7 ± 2.9 and 6.7 ± 7.4 μL of gas, for 30 and 60 s ablation time, respectively. Conclusion  Anodal IRE applications result in significantly less gas formation than both cathodal IRE applications and RF applications. This finding is supported by TOE observations.