Co-Author(s):
Raj Viswanathan, PhD
Pierre Jais, MD
Icahn School of Medicine at Mount Sinai
One Gustave L Levy Place Box 1030
Introduction | Objectives: Pulsed field ablation (PFA) has favorable theoretical and empirically-observed safety benefits for treating atrial fibrillation.   However, it is important to fully understand the unique biophysics of this novel energy source.  Indeed, in vitro studies have shown that electric fields induce dielectrophoretic attraction and, at locally high field strengths, can cause deformation and cellular aggregation by RBC cell membrane electrofusion. Using a multielectrode PFA catheter, we investigated this phenomenon both ex vivo and in vivo .
Methods: An ex vivo model of PFA-induced RBC electrofusion included a beaker with 400-500 mL of defibrinated blood (Lampire Biological Products, PA) stirred magnetically at 30°C.  Using a pentaspline PFA catheter and custom generator (Farapulse Inc), PFA waveforms were delivered up to 2.0 kV.  After multiple runs of 30 PFA deliveries each, any electrode-adherent material was subjectively ranked for extent of deposits by 3 - 5 blinded observers: rank of 1 being least and 15 being most.  A subset of these tests was repeated in vivo inporcine left atria.  Any identified aggregates were sent for histological analysis.
Results: Ex vivo , PFA (using electrical currents 20% higher than used clinically) resulted in trace deposits of adhered, dark-colored material on some distal electrode edges (Figure ).  Consistent with prior reports of RBC electrofusion, histological analysis revealed fused erythrocytes with a small amount of fibrin.  Subjective ranking of deposits was improved after implementing refinements to PFA system architecture and catheter construction (4.3 ± 3.0), vs before (8.8 ± 3.8).  Similar results were observed in vivo : ranks of 5.0 ± 3.9 after implementing refinements, vs before (10.7 ± 3.0).
Conclusions: In ex vivo and in vivo studies, PFA could induce dielectrophoretic attraction of RBCs and, at high local field strengths (not currently being used clinically), can result in electrofusion of cell membranes into macroscopic aggregations.  The propensity for RBC electrofusion is sensitive to alterations in device and waveform parameters.  While the clinical significance of electrofusion is unknown, it would be prudent for PFA systems to be “tuned” to minimize this phenomenon.
AFS2021-56