Preclinical Study of Biphasic Asymmetric Pulsed Field Ablation

Significant hemolysis is present during irreversible electroporation of cardiomyocytes in vitro

BACKGROUND

Pulsed field ablation (PFA) of atrial fibrillation is a new method in clinical practice. Despite a favorable safety profile of PFA in atrial fibrillation ablation, rare cases of renal failure, probably due to hemolysis, have recently been reported.

OBJECTIVE

The aim of this study was to determine the rate of hemolysis and cardiac cell death during in vitro PFA with different electric field intensities.

METHODS

Blood samples from healthy volunteers and mouse HL-1 cardiomyocyte cell lines were subjected to in vitro irreversible electroporation using 216 bipolar pulses, each lasting 2 μs with intervals of 5 μs, repeated 20 times at a frequency of 1 Hz. These pulses varied from 500 V to 1500 V. Cell-free hemoglobin levels were assessed spectrophotometrically, and red blood cell microparticles were evaluated by flow cytometry. Cardiomyocyte death was quantified with propidium iodide.

RESULTS

Pulsed field energy (1000 V/cm, 1250 V/cm, and 1500 V/cm) was associated with a significant increase in cell-free hemoglobin (0.32 ± 0.16 g/L, 2.2 ± 0.96 g/L, and 5.7 ± 0.39 g/L; P < .01) and similar increase in the concentration of red blood cell microparticles. Significant rates of cardiomyocyte death were observed at electric field strengths of 750 V/cm, 1000 V/cm, 1250 V/cm, and 1500 V/cm (26.5% ± 5.9%, 44.3% ± 6.2%, 55.5% ± 6.9%, and 74.5% ± 17.8% of cardiomyocytes; P < .01).

CONCLUSION

The most effective induction of cell death in vitro was observed at 1500 V/cm. This intensity was also associated with a significant degree of hemolysis.

Pulsed Field Ablation for Atrial Fibrillation: Mechanisms, Advantages, and Limitations

Pulsed field ablation with irreversible electroporation for the treatment of atrial fibrillation involves tissue-specific and non-thermal energy-induced cell necrosis, which helps avoid complications, such as pulmonary vein stenosis, atrial collateral tissue damage, and extensive atrial structural damage, often encountered with traditional thermal ablation. In existing clinical trials, pulsed field ablation has shown excellent effects on pulmonary vein isolation in patients with paroxysmal and persistent atrial fibrillation. Pulsed field ablation is easy, simple, and quick and can reduce iatrogenic injury. Therefore, the application of pulsed field ablation technology in the treatment of atrial fibrillation has a promising future. Notably, the adjustment of parameters in pulsed field ablation with different ablation catheter systems can strongly affect the area and depth of the necrotic myocardium, which greatly affects the likelihood of atrial fibrillation recurrence and incidence of adverse complications after ablation. In this paper, we review the mechanisms, advantages, and limitations of pulsed field ablation based on the results of a series of previous studies and provide ideas and directions for future research.

A pilot clinical assessment of biphasic asymmetric pulsed field ablation catheter for pulmonary vein isolation

Pulsed field ablation (PFA) is a new treatment for atrial fibrillation (AF), and its selective ablation characteristics give it a significant advantage in treatment. In previous cellular and animal experiments, we have demonstrated that biphasic asymmetric pulses can be used to ablate myocardial tissue. However, small-scale clinical trials are needed to test whether this approach is safe and feasible before extensive clinical trials can be performed. Therefore, the purpose of this experiment is to determine the safety and feasibility of biphasic asymmetric pulses in patients with AF and is to lay the foundation for a larger clinical trial. Ablation was performed in 10 patients with AF using biphasic asymmetric pulses. Voltage mapping was performed before and after PFA operation to help us detect the change in the electrical voltage of the pulmonary veins (PV). 3-Dimensional mapping system showed continuous low potential in the ablation site, and pulmonary vein isolation (PVI) was achieved in all four PV of the patients. There were no recurrences, PV stenosis, or other serious adverse events during the 12 months follow-up. The results suggest that PFA using biphasic asymmetric waveforms for patients with AF is safe, durable, and effective and that a larger clinical trial could begin.

Clinical Trial Registration

https://www.chictr.org.cn/, identifier, ChiCTR2100051894.

In Vitro Models for Improved Therapeutic Interventions in Atrial Fibrillation

Atrial fibrillation is the most common type of cardiac arrhythmias in humans, mostly caused by hyper excitation of specific areas in the atrium resulting in dyssynchronous atrial contractions, leading to severe consequences such as heart failure and stroke. Current therapeutics aim to target this condition through both pharmacological and non-pharmacological approaches. To test and validate any of these treatments, an appropriate preclinical model must be carefully chosen to refine and optimise the therapy features to correctly reverse this condition. A broad range of preclinical models have been developed over the years, with specific features and advantages to closely mimic the pathophysiology of atrial fibrillation. In this review, currently available models are described, from traditional animal models and in vitro cell cultures to state-of-the-art organoids and organs-on-a-chip. The advantages, applications and limitations of each model are discussed, providing the information to select the appropriate model for each research application.

Study on the process of cardiomyocyte apoptosis after pulsed field ablation

Background

The development of pulsed field ablation (PFA) as a new technique for pulmonary vein isolation (PVI) has been advancing rapidly in recent years. My team's previous work has shown the safety and long-term efficacy of bipolar asymmetric pulses in animal experiments. However, in ongoing clinical trials, we have observed that atrial fibrillation (AF) recurs in some patients after surgery, but the rhythm returns to normal without surgical intervention after seven days, and there is no recurrence in the follow-up.Based on this observation, we have proposed the hypothesis that myocardial cell apoptosis may play a role in AF recurrence after PFA. Our team has designed animal experiments to verify this hypothesis and further investigate the process of PFA-induced cardiomyocyte apoptosis.

Methods

Pulse field ablation was performed on 15 dogs and the animals were dissected at various time points after the operation (immediately, 3 days, 7 days, 30 days, and 150 days). To obtain ablation voltage maps, electroanatomic mapping was performed before and after ablation and before dissection. The ablation area was also subjected to HE and TUNEL staining to analyze apoptosis and pathological results.

Results

The edge area of the ablation in the pulmonary vein (PV) demonstrated continuous dynamic changes from 0 to 2 h after the operation and a slight expansion of the ablation range was observed in the long-term follow-up. Myocardial intima hyperplasia was observed from 0 to 7 days. Local apoptosis was detected from 0 to 2 h and massive, concentrated apoptosis was observed at 3 days. No recurrence of apoptosis was seen at 7 days, 30 days, and 150 days.

Conclusions

The results of this study showed that after pulse field ablation (PFA), the central ablation area of the canine heart experienced immediate cardiomyocyte death. Meanwhile, cardiomyocytes in the edge ablation area underwent apoptosis, which began from 0 to 2 h post-operation and ended between 3 and 7 days. This process occurred simultaneously with intimal thickening.In the long-term follow-up group, there was no recovery of isolation and no recurrence of cardiomyocyte apoptosis, and no change was observed in the endomyocardial intima.