Co-Author(s):
Raju Viswanathan, PhD - Vice President of Research and Development, Farapulse
Vivek Reddy, MD - Director of Cardiac Arrhythmia Services, Mount Sinai
MPMC/CPMC Sutter Health
1501 Trousdale Drive, Burlingame, CA, 94010
Introduction | Objectives: Endocardial pulsed field ablation (PFA) has electrolytic effects that are echogenic and can be altered via device and delivery parameters.  Quantification of PFA-generated ,in comparison with radiofrequency (RF), bubbles can inform PFA’s embolic safety profile.
Methods: The PFA system was described previously1.   A bubble trap described previously was used2. Room temperature saline (4.5 g/L NaCl to mimic clinical impedance) flowing at a rate of 0.8 L/min was used.  PFA was delivered and quantification of gas burden was made with a bubble counter (Gampt BCC300). Gas emission was qualified via ICE echocardiography (RF and PFA). RF applications were made using a commercial system (Boston Scientific Maestro 4000/Blazer Model 9620). The data was compared with published values from an in-vivo RF model3.
Results: 6 scenarios for PFA delivery were investigated (figure 1): free-floating vs in contact with porcine myocardium (tissue), 2.0 vs 1.8kV amplitudes and two catheter shapes. A total of 8 applications were delivered per session per clinical studies1.  Average gas volume and maximal bubble diameter was 1.52±1.44nL and 85 mm, respectively, across all PFA scenarios. RF applications to tissue (excluding steam pops) created an average gas volume (nl) of 177±134 or 59.3±44.7 when adjusted for flow rate2 (factor 0.33), similar to previous data. Saline vs tissue PFA values were similar. Median bubble diameter was smaller with PFA than RF (18 vs 30µm, respectively).  PFA bubbles were visible only on ICE and only during the few seconds of delivery.  RF bubbles were visible via ICE, persisting up to one minute after end of delivery.
Conclusions: Total volume and maximal diameter of bubbles produced with a clinical PFA system were lower when compared with RF values. The density of small-sized bubbles occurring in a short PFA delivery duration contribute to the echogenicity of PFA delivery. Similar results between PFA deliveries to tissue and saline support electrolytic rather than heat-related bubble formation.   References  
AFS 2021-42