Dynamics of local unipolar electrograms during epicardial pulsed field ablation (PFA)
Authors: Garcia-Sanchez T , Amoros-Figueras A , Casabella-Ramon S , Moreno-Weidmann Z , Guerra J M , Ivorra A 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III

Background
The use of irreversible electroporation (IRE) as a method for cardiac ablation in the treatment of cardiac arrhythmias, known as Pulsed Field Ablation (PFA), has rapidly moved from preclinical studies to clinic.
The reference indicator of acute lesion formation during cardiac ablation with thermal techniques consists in recording the local electrical activity changes. In the case of PFA, modifications in the electrical activity have been observed in areas that are not permanently damaged (reversible electroporation) but this is still poorly characterized. Of particular interest from a clinical perspective is to determine how and when the electrical activity of the reversible electroporation areas recovers after PFA.

Purpose
The purpose of this work was to simultaneously characterize the dynamic evolution of local electrograms after PFA in areas exposed to different levels of tissue damage.

Methods
High-density local unipolar electrograms were acquired at baseline, and continuously and during 60 min after each PFA application. The measurements were performed in different points of the right and left ventricular epicardial surface of 5 swine weighing 57±8 kg using an open-chest approach following the Principles of laboratory animal care" (NIH Publication no. 85-23 revised 1985). Under general anesthesia, a median sternotomy was made to create a surgical window. Unipolar electrograms were recorded using a 128-channel electrode matrix attached to the epicardial surface. For PFA ablation, a standard 8F, 3.5 mm tip monopolar catheter was positioned in the region corresponding to the center of the electrode array and a return electrode patch was attached to the back of the animals (see Fig. 1). At least 3 hours after the last ablation point, animals were euthanized and tissue was processed and stained with Triphenyltetrazolium Chloride (TTC) to assess acute lesion morphology.

Results
Our results show an immediate change in the morphology of unipolar electrograms: from basal biphasic electrograms to monophasic electrograms displaying a sudden ST-segment elevation (from 0.0±0.3 mV to 5.9±1.7mv; p&lt;0.01), reduction in the R-S amplitude (from 3.4±3.3 mV to 0.3±0.2 mV; p&lt;0.01) and reduction in the maximum derivative of the QRS-complex (from 3051±2473 mV/s to 394±242 mV/s; p&lt;0.01). Interestingly, the extent and dynamics of the observed changes clearly depended on the ablation level (distance from the ablation point) (see Fig 2.).

Conclusions
Our observations confirmed that the electrical activity of the reversible electroporation area was also acutely modified while the recovery dynamics were different from the irreversible damaged areas. Our preliminary analysis suggests that the different recovery dynamics observed could help in differentiating between reversible and irreversible electroporation areas.