Impact of saline irrigation on haemolysis, silent cerebral lesion incidence, thermal dynamics, and bubble formation in pulsed field ablation with a variable-loop circular catheter

Though pulsed-field ablation (PFA) has demonstrated an excellent safety profile in reducing collateral injury to the oesophagus and phrenic nerve, it is still associated with specific effects, including electrode heating, haemolysis, and electrolysis due to excessive energy dispersion. This study aims to assess whether saline irrigation during PFA application could mitigate these risks.

To comprehensively evaluate the effect of irrigation with the variable-loop circular catheter (VLCC), the following experiments were performed: (i) ex-vivo potato model: to evaluate the lesion depth, bubble formation, and thermal effects in different irrigation regimens; (ii) in vitro blood pool and cardiac ablation: to determine the haemolysis status and tissue temperature change after PFA; (iii) in vivo swine ablation (n = 8), and (iv) clinical randomized trial (n = 25): to compare the efficacy and safety profile between low (4 mL/min) and high (30 mL/min) flow irrigation using the VLCC. Though peak core temperatures at 5 mm depth were all < 50°C under low- and high-irrigation, high irrigation significantly mitigated the instant electrode and deep tissue heating both in the potato and isolated cardiac models. Ex vivo potato slices showed that high-flow irrigation produced the deepest lesion sets when compared to low-flow irrigation (5.94 ± 0.29 mm vs. 5.36 ± 0.33 mm, P = 0.043). Assessment from a high-speed camera and bubble detector demonstrated that high-flow irrigation significantly reduced the total number of gaseous bubbles (54.50 IQR 53.00–56.75 vs. 82.00 IQR 72.00–83.00, P < 0.001) and eliminated the occurrence of larger bubbles. The high-flow irrigation group showed a smaller increase in the level of free haemoglobin immediately after the procedure across the blood pool, swine, and clinical models. Haptoglobin and lactate dehydrogenase levels were also attenuated by high irrigation in the in vivo swine model and clinical trial. One swine in the low-irrigation group developed an acute cerebral lesion (3 mm). The clinical trial confirmed that the incidence of silent cerebral lesions was significantly lower in the high-flow irrigation group (16.7% vs. 66.7%, P = 0.036).

Proper saline irrigation during PFA with VLCC may mitigate electrode-associated haemolysis, reduce electrode and tissue temperature, limit bubble aggregation, and be associated with a lower incidence of silent cerebral lesions, the clinical significance of which remains unclear.