Microbubble and thermal profile of an eight-spline pulsed field ablation system in a pre-clinical model

Pulsed field ablation (PFA) has become a clinically accepted energy modality for catheter ablation of atrial fibrillation. As PFA catheters improve and evolve, iatrogenic cerebral events remain an important consideration when evaluating the safety of new devices. Several factors unique to each PFA system have the potential to lead to embolic events, including but not limited to thermal effects leading to char or coagulum formation and microbubble production.

To characterize the thermal profile and microbubble production from an 8-spline balloon-in-basket PFA catheter.

PFA applications from a 12.5 F, over-the-wire, balloon-in-basket PFA catheter were performed on non-perfused ex vivo bovine tissue. Fiber-optic thermometry probes were used to assess temperature (surface, 3 mm, and 7 mm intramurally) after 8, 16, and 70 consecutive PFA applications. Gross and histopathological assessments were completed to assess for indicators of thermal tissue damage. Microbubble production was evaluated using an extracorporeal blood loop (left femoral vein and right femoral artery loop in N = 6 swine) with an ultrasonic bubble counter and flow meter. For each application, microbubble quantity, size, and gas volume were measured.

None of the ablations resulted in a tissue temperature above 50 °C. A single ablation produced, on average, 187 microbubbles and 30.3 nL of gas. The PFA system produced bubbles with an average diameter of 43 µm. All measures were significantly below the RF derived thresholds of 1174 microbubbles, 1128 nL, and 49 µm, respectively.

This 12.5 F, over-the-wire, balloon-in-basket PFA catheter and associated therapy did not lead to clinically significant temperature rises that may cause thermal necrosis, char, and coagulum. In addition, this PFA catheter produced fewer and smaller microbubbles with less total gas volume compared to radiofrequency (RF) devices with available data.