In vitro analysis of the origin and characteristics of gaseous microemboli during catheter electroporation ablation

Abstract

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.

AC Pulsed Field Ablation Is Feasible and Safe in Atrial and Ventricular Settings: A Proof-of-Concept Chronic Animal Study

“…This can cause gas microemboli with consequent coronary occlusion, stroke or silent cerebral events. To our best knowledge, there is no systematic characterization of this phenomenon for therapies employing DC-PFA, with a notable exception for LifePak9 DCpulses which are characterized in vitro (van Es et al, 2019a). In our experience, DC pulse trains of microseconds can also produce gas bubble stream (Supplementary Video 4).…”

“…DC monophasic pulses are historically the most employed for electroporation of cell suspensions, but they can lead to potentially painful nerve and muscle capture (Mercadal et al, 2017), arcing, metallic release in solution (Meir and Rubinsky, 2014), and bubble stream formation, also due to electrolysis without arcing (van Es et al, 2019a). These issues require a careful control of DC pulses delivery and avoid direct galvanic coupling between electrodes and tissue.…”

Pulsed electrical field in arrhythmia treatment: Current status and future directions

“…Monophasic or biphasic waveform can be used for pulse delivery. Monophasic waveform results in the greatest charging capacity of the cell membrane, creating the strongest damaging effects; however, it may carry the risk of electrically depolarizing surrounding tissues, inducing muscle contraction and gas formation 25,26 . Biphasic waveforms can greatly reduce muscle contraction but will generate weaker damaging effects 27 .…”

Ablation Modalities for Therapeutic Intervention in Arrhythmia-Related Cardiovascular Disease: Focus on Electroporation

“…While IRE overcomes many complications associated with thermal ablation techniques, it does pose some similar risks such as thrombosis, haemorrhage and infection, however these are common to all procedures employing similar access techniques [ 50 ]. Specific to IRE there is an associated risk of electrolysis when untuned current is passed through body fluids with dissolved electrolytes, instigating gas formation [ 97 , 98 ]. One study reported that different current polarity may decrease gas bubble formation as a side-effect of IRE, highlighting that a reduced number of gas bubbles are released when using anodal IRE, compared to RF or cathodal IRE [ 98 ].…”