Intra - operative Anesthesia Management in Patients Undergoing Surgical Irreversible Electroporation of the Pancreas, Liver, Kidney, and Retroperitoneal Tumors

Pulsed Field Energy in Atrial Fibrillation Ablation: From Physical Principles to Clinical Applications

Atrial fibrillation, representing the most prevalent sustained cardiac arrhythmia, significantly impacts stroke risk and cardiovascular mortality. Historically managed with antiarrhythmic drugs with limited efficacy, and more recently, catheter ablation, the interventional approach field is still evolving with technological advances. This review highlights pulsed field ablation (PFA), a revolutionary technique gaining prominence in interventional electrophysiology because of its efficacy and safety. PFA employs non-thermal electric fields to create irreversible electroporation, disrupting cell membranes selectively within myocardial tissue, thus preventing the non-selective damage associated with traditional thermal ablation methods like radiofrequency or cryoablation. Clinical studies have consistently shown PFA's ability to achieve pulmonary vein isolation-a cornerstone of AF treatment-rapidly and with minimal complications. Notably, PFA reduces procedure times and has shown a lower incidence of esophageal and phrenic nerve damage, two common concerns with thermal techniques. Emerging from oncological applications, the principles of electroporation provide a unique tissue-selective ablation method that minimizes collateral damage. This review synthesizes findings from foundational animal studies through to recent clinical trials, such as the MANIFEST-PF and ADVENT trials, demonstrating PFA's effectiveness and safety. Future perspectives point towards expanding indications and refinement of techniques that promise to improve AF management outcomes further. PFA represents a paradigm shift in AF ablation, offering a safer, faster, and equally effective alternative to conventional methods. This synthesis of its development and clinical application outlines its potential to become the new standard in AF treatment protocols.

The Enhancement of Tumor Ablation Effect by the Combination of High-Frequency and Low-Voltage Bipolar Electroporation Pulses

The H-FIRE (high-frequency irreversible electroporation) protocol employs high-frequency bipolar pulses (HFBPs) with a width of ∼1 µs for tumor ablation with slight muscle contraction. However, H-FIRE pulses need a higher electric field to generate a sufficient ablation effect, which may cause undesirable thermal damage.

OBJECTIVE

Recently, combining short high-voltage IRE monopolar pulses with long low-voltage IRE monopolar pulses was shown to enlarge the ablation region. This finding indicates that combining HFBPs with low-voltage bipolar pulses (LVBPs), which are called composited bipolar pulses (CBPs), may enhance the ablation effect.

METHODS

This study designed a pulse generator by modifying a full-bridge inverter. The cell suspension and 3D tumor mimic experiments (U251 cells) were performed to examine the enhancement of the ablation effect.

RESULTS

The generator outputs HFBPs with 0-±2.5 kV and LVBPs with 0-±0.3 kV in one period. The pulse parameters are adjustable by programming on a human-computer interface. The cell suspension experiments showed that CBPs could enhance cytotoxicity, as compared to HFBPs with no cell-killing effect. Even at lower electric energy, the cell viability by CBPs was significantly lower than that of the HFBPs protocol. The ablation experiments on the 3D tumor mimic showed that the CBPs could create a larger connected ablation area. In contrast, the HFBPs protocol with a similar dose generated a nonconnected ablation area.

CONCLUSION

Results indicate that the CBPs protocol can enhance the ablation effect of HFBPs protocol.

SIGNIFICANCE

This proposed generator that uses the CBPs principle may be a useful tool for tumor ablation.

Integrated Time Nanosecond Pulse Irreversible Electroporation (INSPIRE): Assessment of Dose, Temperature, and Voltage on Experimental and Clinical Treatment Outcomes

OBJECTIVE

This study sought to investigate a novel strategy using temperature-controlled delivery of nanosecond pulsed electric fields as an alternative to the 50-100 microsecond pulses used for irreversible electroporation.

METHODS

INSPIRE treatments were carried out at two temperatures in 3D tumor models using doses between 0.001 s and 0.1 s. The resulting treatment zones were quantified using viability staining and lethal electric field intensities were determined numerically. Computational modeling was then used to determine parameters necessary for INSPIRE treatments to achieve equivalent treatment zones to clinical electroporation treatments and evaluate the potential for these treatments to induce deleterious thermal damage.

RESULTS

Lethal thresholds between 1109 and 709 V/cm were found for nominal 0.01 s treatments with pulses between 350 ns and 2000 ns at physiological temperatures. Further increases in dose resulted in significant decreases in lethal thresholds. Given these experimental results, treatment zones comparable to clinical electroporation are possible by increasing the dose and voltage used with nanosecond duration pulses. Temperature-controlled simulations indicate minimal thermal cell death while achieving equivalent treatment volumes to clinical electroporation.

CONCLUSION

Nanosecond electrical pulses can achieve comparable outcomes to traditional electroporation provided sufficient electrical doses or voltages are applied. The use of temperature-controlled delivery may minimize thermal damage during treatment.

SIGNIFICANCE

Intense muscle stimulation and the need for cardiac gating have limited irreversible electroporation. Nanosecond pulses can alleviate these challenges, but traditionally have produced significantly smaller treatment zones. This study suggests that larger ablation volumes may be possible with the INSPIRE approach and that future in vivo studies are warranted.

Effects of bipolar irreversible electroporation with different pulse durations in a prostate cancer mouse model

Irreversible electroporation (IRE) is a non-thermal ablation technique for local tumor treatment known to be influenced by pulse duration and voltage settings, affecting its efficacy. This study aims to investigate the effects of bipolar IRE with different pulse durations in a prostate cancer mouse model. The therapeutic effectiveness was assessed with in vitro cell experiments, in vivo tumor volume changes with magnetic resonance imaging, and gross and histological analysis in a mouse model. The tumor volume continuously decreased over time in all IRE-treated groups. The tumor volume changes, necroptosis (%), necrosis (%), the degree of TUNEL-positive cell expression, and ROS1-positive cell (%) in the long pulse duration-treated groups (300 μs) were significantly increased compared to the short pulse duration-treated groups (100 μs) (all p < 0.001). The bipolar IRE with a relatively long pulse duration at the same voltage significantly increased IRE-induced cell death in a prostate cancer mouse model.

The equivalence of different types of electric pulses for electrochemotherapy with cisplatin - an in vitro study

BACKGROUND

Electrochemotherapy (ECT) is a treatment involving the administration of chemotherapeutics drugs followed by the application of 8 square monopolar pulses of 100 μs duration at a repetition frequency of 1 Hz or 5000 Hz. However, there is increasing interest in using alternative types of pulses for ECT. The use of high-frequency short bipolar pulses has been shown to mitigate pain and muscle contractions. Conversely, the use of millisecond pulses is interesting when combining ECT with gene electrotransfer for the uptake of DNA-encoding proteins that stimulate the immune response with the aim of converting ECT from a local to systemic treatment. Therefore, the aim of this study was to investigate how alternative types of pulses affect the efficiency of the ECT.

MATERIALS AND METHODS

We performed in vitro experiments, exposing Chinese hamster ovary (CHO) cells to conventional ECT pulses, high-frequency bipolar pulses, and millisecond pulses in the presence of different concentrations of cisplatin. We determined cisplatin uptake by inductively coupled plasma mass spectrometry and cisplatin cytotoxicity by the clonogenic assay.

RESULTS

We observed that the three tested types of pulses potentiate the uptake and cytotoxicity of cisplatin in an equivalent manner, provided that the electric field is properly adjusted for each pulse type. Furthermore, we quantified that the number of cisplatin molecules, resulting in the eradication of most cells, was 2-7 × 107 per cell.

CONCLUSIONS

High-frequency bipolar pulses and millisecond pulses can potentially be used in ECT to reduce pain and muscle contraction and increase the effect of the immune response in combination with gene electrotransfer, respectively.

Investigation of integrated time nanosecond pulse irreversible electroporation against spontaneous equine melanoma

Introduction

Integrated time nanosecond pulse irreversible electroporation (INSPIRE) is a novel tumor ablation modality that employs high voltage, alternating polarity waveforms to induce cell death in a well-defined volume while sparing the underlying tissue. This study aimed to demonstrate the in vivo efficacy of INSPIRE against spontaneous melanoma in standing, awake horses.

Methods

A custom applicator and a pulse generation system were utilized in a pilot study to treat horses presenting with spontaneous melanoma. INSPIRE treatments were administered to 32 tumors across 6 horses and an additional 13 tumors were followed to act as untreated controls. Tumors were tracked over a 43-85 day period following a single INSPIRE treatment. Pulse widths of 500ns and 2000ns with voltages between 1000 V and 2000 V were investigated to determine the effect of these variables on treatment outcomes.

Results

Treatments administered at the lowest voltage (1000 V) reduced tumor volumes by 11 to 15%. Higher voltage (2000 V) treatments reduced tumor volumes by 84 to 88% and eliminated 33% and 80% of tumors when 500 ns and 2000 ns pulses were administered, respectively.

Discussion

Promising results were achieved without the use of chemotherapeutics, the use of general anesthesia, or the need for surgical resection in regions which are challenging to keep sterile. This novel therapeutic approach has the potential to expand the role of pulsed electric fields in veterinary patients, especially when general anesthesia is contraindicated, and warrants future studies to demonstrate the efficacy of INSPIRE as a solid tumor treatment.

Irreversible Electroporation in Pancreatic Cancer-An Evolving Experimental and Clinical Method

Pancreatic cancer has no symptoms until the disease has advanced and is aggressive cancer with early metastasis. Up to now, the only curative treatment is surgical resection, which is possible in the early stages of the disease. Irreversible electroporation treatment offers new hope for patients with unresectable tumors. Irreversible electroporation (IRE) is a type of ablation therapy that has been explored as a potential treatment for pancreatic cancer. Ablation therapies involve the use of energy to destroy or damage cancer cells. IRE involves using high-voltage, low-energy electrical pulses to create resealing in the cell membrane, causing the cell to die. This review summarizes experiential and clinical findings in terms of the IRE applications. As was described, IRE can be a non-pharmacological approach (electroporation) or combined with anticancer drugs or standard treatment methods. The efficacy of irreversible electroporation (IRE) in eliminating pancreatic cancer cells has been demonstrated through both in vitro and in vivo studies, and it has been shown to induce an immune response. Nevertheless, further investigation is required to assess its effectiveness in human subjects and to comprehensively understand IRE's potential as a treatment option for pancreatic cancer.

Irreversible Electroporation-Assisted Resection for Locally Advanced Pancreas Cancer

BACKGROUND

A significant number of patients with advanced pancreatic cancer are unable to undergo resection due to vascular involvement. Irreversible electroporation (IRE) has shown promise in improving survival. This study sought to assess a novel IRE application whereby IRE was performed pre-resection to alter tissue plasticity and assist tumor removal from underlying vasculature when surgical excision was otherwise precluded.

METHODS

After multidisciplinary evaluation appropriate patients were consented for IRE therapy. All IRE cases were tracked prospectively using an institutional review board-approved database that was retrospectively queried for patients undergoing IRE-assisted resection (IRE-AR) for pancreatic adenocarcinoma located in the head/uncinate process. Patients who underwent other IRE therapy or had disease location elsewhere were excluded.

RESULTS

5 patients met the study inclusion criteria with a mean tumor size of 3.2 cm (range 2.4-4.1 cm). Using IRE-AR median recurrence free survival was 10.6 months, with 21.6 month overall survival. The average comprehensive complication index score was 23.23. One patient had grade 3 [or higher] complications and there were no 90 day mortalities.

DISCUSSION

Employing a high-starting voltage for ablation along resection margins allows for resection when margins are anticipated to be positive. Patients with locally advanced pancreatic adenocarcinoma who underwent IRE-AR had promising outcomes.

CONCLUSION

This study reports IRE-AR as a novel approach for resecting locally advanced pancreatic adenocarcinoma. A prospective trial of IRE-AR for inoperable pancreatic adenocarcinoma will provide additional data for the long-term application of this approach.

Muscle contractions and pain sensation accompanying high-frequency electroporation pulses

To minimize neuromuscular electrical stimulation during electroporation-based treatments, the replacement of long monophasic pulses with bursts of biphasic high-frequency pulses in the range of microseconds was suggested in order to reduce muscle contraction and pain sensation due to pulse application. This treatment modality appeared under the term high-frequency electroporation (HF-EP), which can be potentially used for some clinical applications of electroporation such as electrochemotherapy, gene electrotransfer, and tissue ablation. In cardiac tissue ablation, which utilizes irreversible electroporation, the treatment is being established as Pulsed Field Ablation. While the reduction of muscle contractions was confirmed in multiple in vivo studies, the reduction of pain sensation in humans was not confirmed yet, nor was the relationship between muscle contraction and pain sensation investigated. This is the first study in humans examining pain sensation using biphasic high-frequency electroporation pulses. Twenty-five healthy individuals were subjected to electrical stimulation of the tibialis anterior muscle with biphasic high-frequency pulses in the range of few microseconds and both, symmetric and asymmetric interphase and interpulse delays. Our results confirm that biphasic high-frequency pulses with a pulse width of 1 or 2 µs reduce muscle contraction and pain sensation as opposed to currently used longer monophasic pulses. In addition, interphase and interpulse delays play a significant role in reducing the muscle contraction and/or pain sensation. The study shows that the range of the optimal pulse parameters may be increased depending on the prerequisites of the therapy. However, further evaluation of the biphasic pulse protocols presented herein is necessary to confirm the efficiency of the newly proposed HF-EP.

Irreversible Electroporation (IRE) Combined With Chemotherapy Increases Survival in Locally Advanced Pancreatic Cancer (LAPC)

OBJECTIVES

Locally advanced pancreatic cancer (LAPC) is found in about 40% of patients with pancreatic cancer. Irreversible electroporation (IRE) is a nonthermal ablative technique that provides an alternative in patients with LAPC and can be safely combined with chemotherapy.

MATERIALS AND METHODS

From 2015 until October of 2019, we performed laparotomic IRE in a total of 40 patients with stage III LAPC. The median age of these patients was 65.2 years (range: 46 to 81 y), and the median tumor size was 3.8 cm (range: 2 to 5.2 cm). 33 of 40 patients were treated preoperatively with FOLFIRINOX or nab-paclitaxel plus gemcitabine and in case of disease control, IRE was performed, whereas in 7 patients, IRE was performed without previous chemotherapy.

RESULTS

All patients were treated successfully with IRE as the tumor evaluation showed no disease progression after the completion of induction chemotherapy. No IRE-related deaths occurred. Two major grade III complications were reported: pancreatic fistula grade A in 8 patients and 3 patients diagnosed with delayed gastric emptying. Up to October 31, 2019, the median overall survival (OS) of all patients was 24.2 months (range: 6 to 36 mo), and the median progression-free survival was 10.3 months (range: 3 to 24 mo). After the completion of IRE, 30 patients (75%) continued with adjuvant chemotherapy. Fifteen patients (37%) have >24 months OS and 3 patients (8%) have reached 36 months OS and are still alive.

CONCLUSION

The combination of chemotherapy with IRE, which is a safe and effective procedure, may result in a survival benefit for patients with LAPC.

A Theoretical Argument for Extended Interpulse Delays in Therapeutic High-Frequency Irreversible Electroporation Treatments

High-frequency irreversible electroporation (H-FIRE) is a tissue ablation modality employing bursts of electrical pulses in a positive phase-interphase delay (d1)-negative phase-interpulse delay (d2) pattern. Despite accumulating evidence suggesting the significance of these delays, their effects on therapeutic outcomes from clinically-relevant H-FIRE waveforms have not been studied extensively.

OBJECTIVE

We sought to determine whether modifications to the delays within H-FIRE bursts could yield a more desirable clinical outcome in terms of ablation volume versus extent of tissue excitation.

METHODS

We used a modified spatially extended nonlinear node (SENN) nerve fiber model to evaluate excitation thresholds for H-FIRE bursts with varying delays. We then calculated non-thermal tissue ablation, thermal damage, and excitation in a clinically relevant numerical model.

RESULTS

Excitation thresholds were maximized by shortening d1, and extension of d2 up to 1,000 μs increased excitation thresholds by at least 60% versus symmetric bursts. In the ablation model, long interpulse delays lowered the effective frequency of burst waveforms, modulating field redistribution and reducing heat production. Finally, we demonstrate mathematically that variable delays allow for increased voltages and larger ablations with similar extents of excitation as symmetric waveforms.

CONCLUSION

Interphase and interpulse delays play a significant role in outcomes resulting from H-FIRE treatment.

SIGNIFICANCE

Waveforms with short interphase delays (d1) and extended interpulse delays (d2) may improve therapeutic efficacy of H-FIRE as it emerges as a clinical tissue ablation modality.

Development of adaptive resistance to electric pulsed field treatment in CHO cell line in vitro

Pulsed electric field treatment has increased over the last few decades with successful translation from in vitro studies into different medical treatments like electrochemotherapy, irreversible electroporation for tumor and cardiac tissue ablation and gene electrotransfer for gene therapy and DNA vaccination. Pulsed electric field treatments are efficient but localized often requiring repeated applications to obtain results due to partial response and recurrence of disease. While these treatment times are several orders of magnitude lower than conventional biochemical treatment, it has been recently suggested that cells may become resistant to electroporation in repetitive treatments. In our study, we evaluate this possibility of developing adaptive resistance in cells exposed to pulsed electric field treatment over successive lifetimes. Mammalian cells were exposed to electroporation pulses for 30 generations. Every 5th generation was analyzed by determining permeabilization and survival curve. No statistical difference between cells in control and cells exposed to pulsed electric field treatment was observed. We offer evidence that electroporation does not affect cells in a way that they would become less susceptible to pulsed electric field treatment. Our findings indicate pulsed electric field treatment can be used in repeated treatments with each treatment having equal efficiency to the initial treatment.

Electro-Thermal Therapy Algorithms and Active Internal Electrode Cooling Reduce Thermal Injury in High Frequency Pulsed Electric Field Cancer Therapies

Thermal tissue injury is an unintended consequence in current irreversible electroporation treatments due to the induction of Joule heating during the delivery of high voltage pulsed electric fields. In this study active temperature control measures including internal electrode cooling and dynamic energy delivery were investigated as a process for mitigating thermal injury during treatment. Ex vivo liver was used to examine the extent of thermal injury induced by 5000 V treatments with delivery rates up to five times faster than current clinical practice. Active internal cooling of the electrode resulted in a 36% decrease in peak temperature vs. non-cooled control treatments. A temperature based feedback algorithm (electro-thermal therapy) was demonstrated as capable of maintaining steady state tissue temperatures between 30 and 80 °C with and without internal electrode cooling. Thermal injury volumes of 2.6 cm³ were observed for protocols with 60 °C temperature set points and electrode cooling. This volume reduced to 1.5 and 0.1 cm³ for equivalent treatments with 50 °C and 40 °C set points. Finally, it was demonstrated that the addition of internal electrode cooling and active temperature control algorithms reduced ETT treatment times by 84% (from 343 to 54 s) vs. non-cooled temperature control strategies with equivalent thermal injury volumes.

Prevention of Procedural Hypertension in the Irreversible Electroporation Ablation of Liver and Pancreatic Tumors Based on Distance from the Adrenal Gland

Background and objective

When irreversible electroporation (IRE) ablation of abdominal tumors, procedural hypertension often occurs, which often affects the progress of the ablation. Until now, there is no reasonable explanation for this phenomenon. The objective of this research was to explore the cause and solution of procedural hypertension in percutaneous IRE.

Methods

In this study, the treatment data of 4 consecutive groups of patients were used to confirm the cause of intraoperative hypertension and then verify the solution. A total of 155 patients with procedural hypertension were screened based on their medical records of pancreatic or hepatic IRE treatment. Procedural hypertension was monitored in 21 new patients, the correlation between serum catecholamines and hypertension was recorded and evaluated using regression analysis. Forty new patients were divided into two groups (distance from needle tip to adrenal gland, < 2 cm vs ≥ 2 cm), and the blood pressure was recorded and compared with two-way ANOVA. Eleven patients with ablative distance <2 cm were treated in advance with phentolamine to observe for the occurrence of procedural hypertension.

Results

Of the 21 re-enrolled patients with ablation of the pancreas and liver tumors, 9 developed intraoperative hypertension with significantly elevated serum catecholamines levels, epinephrine, norepinephrine and dopamine are all positively associated with hypertension, with P values were 0.0003, 0.0253, and 0.0015, respectively. For the two groups with different needle-insertion distances, hypertension in the < 2 cm group was more significant than that in the other group (for procedural hypertension, P< 0.01; for heart rate, P< 0.05), which was considered as a high-risk group. The occurrence of intraoperative hypertension could be completely prevented by using phentolamine prior to treatment.

Conclusion

Hypertension occurs frequently during hepatic and pancreatic IRE because of the damage of adrenal gland. The safe distance of ablation probe for the adrenal gland was 2 cm. For high-risk patients, early drug prevention works well.

Cancellation effect is present in high-frequency reversible and irreversible electroporation

It was recently suggested that applying high-frequency short biphasic pulses (HF-IRE) reduces pain and muscle contractions in electrochemotherapy and irreversible ablation treatments; however, higher amplitudes with HF-IRE pulses are required to achieve a similar effect as with monophasic pulses. HF-IRE pulses are in the range of a microseconds, thus, the so-called cancellation effect could be responsible for the need to apply pulses of higher amplitudes. In cancellation effect, the effect of first pulse is reduced by the second pulse of opposite polarity. We evaluated cancellation effect with high-frequency biphasic pulses on CHO-K1 in different electroporation buffers. We applied eight bursts of 1-10 µs long pulses with inter-phase delays of 0.5 µs - 10 ms and evaluated membrane permeability and cell survival. In permeability experiments, cancellation effect was not observed in low-conductivity buffer. Cancellation effect was, however, observed in treatments with high-frequency biphasic pulses looking at survival in all of the tested electroporation buffers. In general, cancellation effect depended on inter-phase delay as well as on pulse duration, i.e. longer pulses and longer interphase delay cause less pronounced cancellation effect. Cancellation effect could be partially explained by the assisted discharge and not by the hyperpolarization by the chloride channels.

Intraoperative Irreversible Electroporation in Locally Advanced Pancreatic Cancer: A Guide for the Interventional Radiologist

Efforts to improve mortality associated with locally advanced pancreatic cancer (LAPC) have shown minimal gains despite advances in surgical technique, systemic treatments, and radiation therapy. Locoregional therapy with ablation has not been routinely adopted due to the high risk of complications associated with thermal destruction of the pancreas. Irreversible electroporation (IRE) is an emerging, nonthermal, ablative technology that has demonstrated the ability to generate controlled ablation of LAPC while preserving pancreatic parenchymal integrity. IRE may be performed percutaneously or via laparotomy and will commonly involve multidisciplinary treatment teams. This article will describe the technical aspects of how multidisciplinary IRE is performed during laparotomy at a single tertiary care institution.

High-Frequency Irreversible Electroporation Using 5,000-V Waveforms to Create Reproducible 2- and 4-cm Ablation Zones-A Laboratory Investigation Using Mechanically Perfused Liver

PURPOSE

To investigate if high-frequency irreversible electroporation (H-FIRE) treatments can be delivered at higher voltages and with greater energy delivery rates than currently implemented in clinical irreversible electroporation protocols.

MATERIALS AND METHODS

Treatments using 3,000 V and 5,000 V were administered to mechanically perfused ex vivo porcine liver via a single applicator and grounding pad (A+GP) as well as a 4-applicator array (4AA). Integrated energized times (IET) 0.01-0.08 seconds and energy delivery rates 25-300 μs/s were investigated. Organs were preserved at 4°C for 10-15 hours before sectioning and gross analysis using a metabolic stain to identify the size and shape of ablation zones.

RESULTS

A+GP ablations measured between 1.6 cm and 2.2 cm, which did not increase when IET was increased from 0.02 seconds to 0.08 seconds (P > .055; range, 1.9-2.1 cm). Changes in tissue color and texture consistent with thermal damage were observed for treatments with energy delivery rates 50-300 μs/s, but not for treatments delivered at 25 μs/s. Use of the 4AA with a 3-cm applicator spacing resulted in ablations measuring 4.4-4.9 cm with energy delivery times of 7-80 minutes.

CONCLUSIONS

H-FIRE treatments can rapidly and reproducibly create 2-cm ablations using an A+GP configuration. Treatments without thermal injury were produced at the expense of extended treatment times. More rapid treatments resulted in ablations with varying degrees of thermal injury within the H-FIRE ablation zone. Production of 4-cm ablations is possible using a 4AA.

The combination of electroporation and electrolysis (E2) employing different electrode arrays for ablation of large tissue volumes

Background

The combination of electroporation with electrolysis (E2) has previously been introduced as a novel tissue ablation technique. E2 allows the utilization of a wide parameter range and may therefore be a suitable technology for development of tissue-specific application protocols. Previous studies have implied that it is possible to achieve big lesions in liver in a very short time. The goal of this study was to test a variety of electrode configurations for the E2 application to ablate large tissue volumes.

Materials and methods

27 lesions were performed in healthy porcine liver of five female pigs. Four, two and bipolar electrode-arrays were used to deliver various E2 treatment protocols. Liver was harvested approx. 20h after treatment and examined with H&E and Masson’s trichrome staining, and via TUNEL staining for selective specimen.

Results

All animals survived the treatments without complications. With four electrodes, a lesion of up to 35x35x35mm volume can be achieved in less than 30s. The prototype bipolar electrode created lesions of 50x18x18mm volume in less than 10s. Parameters for two-electrode ablations with large exposures encompassing large veins were found to be good in terms of vessel preservation, but not optimal to reliably close the gap between the electrodes.

Conclusion

This study demonstrates the ability to produce large lesions in liver within seconds at lower limits of the E2 parameter space at different electrode configurations. The applicability of E2 for single electrode ablations was demonstrated with bipolar electrodes. Parameters for large 4-electrode ablation volumes were found suitable, while parameters for two electrodes still need optimization. However, since the parameter space of E2 is large, it is possible that for all electrode geometries optimal waveforms and application protocols for specific tissues will emerge with continuing research.

Irreversible electroporation ablation of end-stage metastatic retroperitoneal lesions: Report on three cases and literature review

Metastatic retroperitoneal tumors constitute an end-stage disease with poor prognosis that represents a heavy global health burden. The present study aimed to explore the efficacy of irreversible electroporation ablation (IRE) therapy in patients with end-stage retroperitoneal tumors. Between April 2016 and September 2017, three patients with unresectable retroperitoneal malignant tumors were enrolled. Among these cases, ultrasound (US)-guided IRE was palliatively performed for targeting 3 tumors (1 tumor per patient) located around the abdominal aorta. Post-treatment contrast-enhanced US (CEUS) and contrast-enhanced computed tomography (CECT) scans were subsequently performed to evaluate the area adjacent to the ablation zone and determine the prognosis. During the follow-up, the cases experienced a reduction of pain (mean score of 5.8 decreased to 2.2, based on the visual analogue scale), and had an overall survival rate ranging from 2 to 11 months. Case 1 remained alive at the time of submission of this study, but case 2 died within 2 months and case 3 within 11 months due to liver metastases of the primary tumor. At the 3-week follow-up, the CEUS image for case 1 exhibited a contrast defect with a sufficient ablation margin, in accordance with the CECT at 1.5 months following IRE, exhibiting complete tumor necrosis without contrast enhancement. Overall, these results suggest that US-guided percutaneous IRE may be effective in the treatment of end-stage retroperitoneal tumors. However, further studies are required to substantiate the conclusions of the present study. The present clinical trial was registered at clinicaltrials.gov (ID: NCT02822066) on June 20th, 2016.

Numerical workflow of irreversible electroporation for deep-seated tumor

The paper provides a numerical workflow, based on the 'real-life' clinical workflow of irreversible electroporation (IRE) performed for the treatment of deep-seated liver tumors. Thanks to a combination of numerical modeling, image registration algorithm and clinical data, our numerical workflow enables to provide the distribution of the electric field as effectively delivered by the clinical IRE procedure. As a proof of concept, we show on a specific clinical case of IRE ablation of liver tumor that clinical data could be advantageously combined to numerical simulations in a near future, in order to give to the interventional radiologists information on the effective IRE ablation. We also corroborate the simulated treated region with the post-treatment MRI performed 3 d after the treatment.

Scaling Relationship of In Vivo Muscle Contraction Strength of Rabbits Exposed to High-Frequency Nanosecond Pulse Bursts

We studied the influence of various parameters of high-frequency nanosecond pulse bursts on the strength of rabbit muscle contractions. Ten unipolar high-frequency pulse bursts with various field intensities E (1 kV/cm, 4 kV/cm, and 8 kV/cm), intraburst frequencies f (10 kHz, 100 kHz, and 1 MHz), and intraburst pulse numbers N (1, 10, and 100) were applied using a pair of plate electrodes to the surface skin of the rabbits' biceps femoris, and the acceleration signal of muscle contraction near the electrode was measured using a 3-axis acceleration sensor. A time- and frequency-domain analysis of the acceleration signals showed that the peak value of the signal increases with the increasing strength of the pulse burst and that the frequency spectra of the signals measured under various pulse bursts have characteristic frequencies (at approximately 2 Hz, 32 Hz, 45 Hz, and 55 Hz). Furthermore, we processed the data through multivariate nonlinear regression analysis and variance analysis and determined that the peak value of the signal scales with the logarithm to the base 10 of EN ^x, where x is a value that scales with the logarithm to the base 10 of intraburst frequency (f). These results indicate that for high-frequency nanosecond pulse treatment of solid tumors in or near muscles, when the field strength is relatively high, the intraburst frequency and the intraburst pulse number require appropriate selection to limit the strength of muscle contraction as much as possible.

Safety and efficacy of irreversible electroporation in the treatment of obstructive jaundice in advanced hilar cholangiocarcinoma

BACKGROUND

Irreversible electroporation (IRE) has successfully been used for palliation of pancreatic and liver cancers due to its ability to ablate tumors without destroying nearby vital structures. To date, it has not been evaluated in patients with advanced hilar cholangiocarcinoma (AHC). This study presents a single-institution experience with IRE for management of obstructive jaundice in AHC.

METHODS

A single-institution database was queried for patients undergoing IRE for AHC after PTBD placement for relief of obstructive jaundice from 2010 to 2017 and compared to a control group treated with standard of care only (No IRE).

RESULTS

Twenty-six patients underwent IRE for AHC after PTBD replacement. Three patients experienced complications, with two experiencing severe (≥ grade 3) complications. After IRE, median time to PTBD removal was 122 days (range 0-305 days) and median catheter-free time before requiring PTBD replacement was 305 days (range 92-458 days). In comparison, the 137 control patients had an admission rate of 59% (N = 80 patients) for PTBD infection, occlusion, or catheter related problem.

CONCLUSION

IRE safely achieves biliary decompression via tumor electroporation and allows PTBD removal for an extended period of time. In appropriately selected patients with obstructive jaundice in the setting of AHC, IRE can be used to increase catheter-free days and optimize overall quality of life.

The efficacy of combination of induction chemotherapy and irreversible electroporation ablation for patients with locally advanced pancreatic adenocarcinoma

BACKGROUND AND OBJECTIVES

Irreversible electroporation (IRE) is a non-thermal focal therapy that utilizes high voltage electric pulses to permanently rupture the cellular membrane and induce cell death. In this multi-center study, we evaluated the safety and efficacy of IRE in patients with locally advanced pancreatic cancer (LAPC).

METHODS

From 2012 to 2015, we performed laparotomic and laparoscopic IRE in a total of 70 patients with stage III LAPC. Either gemcitabine-based or TS-1 (Tegafur, Gimeracil, and Oteracil) chemotherapy was applied for at least 3 months before the IRE.

RESULTS

No IRE-related deaths occurred. A median follow-up of 28.1 months showed that six patients (8.6%) experienced local recurrence and 24 (34%) experienced distant progression. The overall median survival from the time of treatment was 22.6 months, and the progression-free survival (PFS) was 15.4 months. The overall survival in the patients who used gemcitabine-based reagents was 19.1 months and that of those who used TS-1 was 28.7 months. The PFS for these two groups were 13.2 months and 26.4 months; the difference is significant.

CONCLUSIONS

Our study suggests that IRE is safe and effective for the control of LAPC. We surmise that the addition of IRE to a chemotherapy regimen may provide a survival advantage.

Reduction of Muscle Contractions during Irreversible Electroporation Therapy Using High-Frequency Bursts of Alternating Polarity Pulses: A Laboratory Investigation in an Ex Vivo Swine Model

PURPOSE

To compare the intensity of muscle contractions in irreversible electroporation (IRE) treatments when traditional IRE and high-frequency IRE (H-FIRE) waveforms are used in combination with a single applicator and distal grounding pad (A+GP) configuration.

MATERIALS AND METHODS

An ex vivo in situ porcine model was used to compare muscle contractions induced by traditional monopolar IRE waveforms vs high-frequency bipolar IRE waveforms. Pulses with voltages between 200 and 5,000 V were investigated, and muscle contractions were recorded by using accelerometers placed on or near the applicators.

RESULTS

H-FIRE waveforms reduced the intensity of muscle contractions in comparison with traditional monopolar IRE pulses. A high-energy burst of 2-μs alternating-polarity pulses energized for 200 μs at 4,500 V produced less intense muscle contractions than traditional IRE pulses, which were 25-100 μs in duration at 3,000 V.

CONCLUSIONS

H-FIRE appears to be an effective technique to mitigate the muscle contractions associated with traditional IRE pulses. This may enable the use of voltages greater than 3,000 V necessary for the creation of large ablations in vivo.

Characterization of Conductivity Changes During High-Frequency Irreversible Electroporation for Treatment Planning

For irreversible-electroporation (IRE)-based therapies, the underlying electric field distribution in the target tissue is influenced by the electroporation-induced conductivity changes and is important for predicting the treatment zone.

OBJECTIVE

In this study, we characterized the liver tissue conductivity changes during high-frequency irreversible electroporation (H-FIRE) treatments of widths 5 and 10 μs and proposed a method for predicting the ablation zones.

METHODS

To achieve this, we created a finite-element model of the tissue treated with H-FIRE and IRE pulses based on experiments conducted in an in-vivo rabbit liver study. We performed a parametric sweep on a Heaviside function that captured the tissue conductivity versus electric field behavior to yield a model current close to the experimental current during the first burst/pulse. A temperature module was added to account for the current increase in subsequent bursts/pulses. The evolution of the electric field at the end of the treatment was overlaid on the experimental ablation zones determined from hematoxylin and eosin staining to find the field thresholds of ablation.

RESULTS

Dynamic conductivity curves that provided a statistically significant relation between the model and experimental results were determined for H-FIRE. In addition, the field thresholds of ablation were obtained for the tested H-FIRE parameters.

CONCLUSION

The proposed numerical model can simulate the electroporation process during H-FIRE.

SIGNIFICANCE

The treatment planning method developed in this study can be translated to H-FIRE treatments of different widths and for different tissue types.

Treatment of Cancer In Vitro Using Radiation and High-Frequency Bursts of Submicrosecond Electrical Pulses

High-frequency irreversible electroporation (H-FIRE) is an emerging cancer therapy, which uses bursts of short duration, alternating polarity, high-voltage electrical pulses to focally ablate tumors. Here, we present a preliminary investigation of the combinatorial effects of H-FIRE and ionizing radiation. In vitro cell cultures were exposed to bursts of 500 ns pulses and single radiation doses of 2 or 20 Gy then analyzed for 14 days. H-FIRE and radiation therapy (RT) appear to induce different delayed cell death mechanisms and in all treatment groups combinatorial therapy resulted in lower overall viabilities. These results indicate that in vivo investigation of the antitumor efficacy of combined H-FIRE and RT is warranted.

Raising the pressure: Hemodynamic effects of splanchnic nerve stimulation

A number of cardiovascular and neurological diseases are characterized by a dysregulation of intravascular volume distribution. The veins and arteries of the visceral organs form the so-called splanchnic vascular compartment and are the largest reservoir for intravascular blood. The blood localized in the splanchnic compartment can be mobilized in and out of the compartment via passive compression or active neurohormonal recruitment. We studied the hemodynamic effects of splanchnic nerve stimulation during five cases of irreversible electroporation (IRE) in patients with pancreatic cancer. In IRE, repeated bursts of high-voltage electrical fields are applied to visceral beds for >1 min, which induces rapid increase in blood pressure, heart rate, and cardiac output. We present the first analysis into the hemodynamic changes with splanchnic nerve stimulation and explore potential mechanisms of the hyperdynamic state. Our analysis presents the first human report of splanchnic nerve stimulation to induce hypertension and volume redistribution, introducing the splanchnic nerves as a key component of cardiovascular regulation.

NEW & NOTEWORTHY Our case series provides the first detailed description of human hemodynamic effects with splanchnic nerve stimulation. Splanchnic nerve stimulation results in profound hemodynamic alteration with rapid onset of hypertension and blood mobilization.

Bipolar Microsecond Pulses and Insulated Needle Electrodes for Reducing Muscle Contractions During Irreversible Electroporation

OBJECTIVE

To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo.

METHODS

An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer.

RESULTS

With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined.

CONCLUSION

This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction.

SIGNIFICANCE

The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE.

Irreversible Electroporation for Locally Advanced Pancreatic Cancer: Where Do We Stand in 2017?

Pancreatic adenocarcinoma has a very poor prognosis. Complete surgical resection remains the only current curative treatment. Locally advanced pancreatic cancers are considered as unresectable because of involvement of celiac and/or mesenteric vessels. Irreversible electroporation has recently been introduced to induce permanent cell death by apoptosis. Irreversible electroporation is a nonthermal cell-destruction technique that was claimed to allow destruction of cancerous cells with less damage to surrounding supporting connective tissues with collagenic structure (such as nearby blood vessels, biliary ducts, and nerves) than other types of treatment. Applications on pancreatic adenocarcinoma seem promising, and this article is an up-to-date review of the first results.

Asymmetric Waveforms Decrease Lethal Thresholds in High Frequency Irreversible Electroporation Therapies

Irreversible electroporation (IRE) is a promising non-thermal treatment for inoperable tumors which uses short (50-100 μs) high voltage monopolar pulses to disrupt the membranes of cells within a well-defined volume. Challenges with IRE include complex treatment planning and the induction of intense muscle contractions. High frequency IRE (H-FIRE) uses bursts of ultrashort (0.25-5 μs) alternating polarity pulses to produce more predictable ablations and alleviate muscle contractions associated with IRE. However, H-FIRE generally ablates smaller volumes of tissue than IRE. This study shows that asymmetric H-FIRE waveforms can be used to create ablation volumes equivalent to standard IRE treatments. Lethal thresholds (LT) of 505 V/cm and 1316 V/cm were found for brain cancer cells when 100 μs IRE and 2 μs symmetric H-FIRE waveforms were used. In contrast, LT as low as 536 V/cm were found for 2 μs asymmetric H-FIRE waveforms. Reversible electroporation thresholds were 54% lower than LTs for symmetric waveforms and 33% lower for asymmetric waveforms indicating that waveform symmetry can be used to tune the relative sizes of reversible and irreversible ablation zones. Numerical simulations predicted that asymmetric H-FIRE waveforms are capable of producing ablation volumes which were 5.8-6.3x larger than symmetric H-FIRE waveforms indicating that in vivo investigation of asymmetric waveforms is warranted.

Irreversible electroporation in locally advanced pancreatic cancer: A call for standardization of energy delivery

Irreversible Electroporation (IRE) is used to treat locally advanced cancers, commonly of the pancreas, liver, kidney, and other soft tissues. Precise eligibility for IRE should be established in each individual patient by a multidisciplinary team based on comprehensive clinical, imaging, and laboratory assessment. Standardization of IRE technique and protocols is expected to improve safety, lead to reproducible outcomes, and facilitate further research into IRE. The present article provides a set of technical recommendations for the use of IRE in the treatment of locally advanced pancreatic cancer. J. Surg. Oncol. 2016;114:865-871. © 2016 2016 Wiley Periodicals, Inc.

Intraoperative adverse events during irreversible electroporation-a call for caution

BACKGROUND

Irreversible electroporation is increasingly used for treatment of solid tumors, but safety data remain scarce. This study aimed to describe intraoperative adverse events associated with irreversible electroporation in patients undergoing solid tumor ablation.

METHODS

We analyzed demographic and intraoperative data for patients (n = 43) undergoing irreversible electroporation for hepato-pancreato-biliary and retroperitoneal malignancies (2012 to 2015). Adverse events were defined as cardiac, surgical, or equipment-related.

RESULTS

Adverse events (n = 20, 47%) were primarily cardiac (90%, n = 18), including blood pressure elevation (77%, n = 14/18) and arrhythmia (16%, n = 7/43). All but one was managed medically, 1 patient with arrhythmia required termination of ablation. Bleeding and technical problems with the equipment occurred in 1 patient each. Multivariable analysis revealed previous cardiovascular disease and needle placement close to the celiac trunk associated with increased likelihood for cardiac events.

CONCLUSIONS

Intraoperative cardiac adverse events are common during irreversible electroporation but rarely impair completion of the procedure.

Selective effect of irreversible electroporation on parenchyma of the pancreas and its vascular structures - an in vivo experiment on a porcine model

Irreversible electroporation is a local, non-thermal ablation method, where short electrical pulses of high voltage lead to changes in cell membrane permeability and cell death. Recent experimental studies have shown that it does not lead to damage of blood vessels, nerves, bile duct or ureters. The aim of our experimental study was to evaluate the negative effect of irreversible electroporation regarding damage to the vascular wall and porcine pancreatic tissue. Irreversible electroporation of the pancreas was performed in 6 pigs after medial laparotomy. Irreversible electroporation was applied to each pig to the splenic lobe of the pancreas in order to assess damage to the pancreatic tissue and to the duodenal lobe of the pancreas to assess damage to the vascular structure of the pancreatic tissue. Higher ablation electric intensity (minimum 500 V/cm – maximum 1,750 V/cm, step 250 V/cm) in 90 μs pulses was utilized on each pig. After 7 days, macroscopic and microscopic evaluations of en bloc resected specimen (pancreas with duodenum) were performed. During 7 post-ablation days, no deaths or clinical worsening occurred in any of the pigs. Necrotic changes in the pancreatic tissue were recorded at an electric intensity of 750 V/cm. Changes in the outer layers of the wall of the arteries and veins occurred at 1,000 V/cm. Transmural vascular wall damage was not recorded in any case. Irreversible electroporation allows for relatively efficient cell death in the target tissues. Our independent experimental work confirms the safety of this method towards vascular structures located in the ablation zone.

Evaluation of tolerability and efficacy of irreversible electroporation (IRE) in treatment of Child-Pugh B (7/8) hepatocellular carcinoma (HCC)

INTRODUCTION

Few studies have assessed the tolerability and efficacy of irreversible electroporation (IRE) in the treatment of Child-Pugh B (7/8) patients with hepatocellular carcinoma (HCC). Based on its mechanism of action, we hypothesized that IRE would be superior to microwave (MW) ablation and compared the liver tolerance and ablation success rates of these therapies in Child-Pugh B patients with HCC.

METHODS

55 patients with Child-Pugh B (7/8) HCC were treated with either MW ablation (n = 25) or IRE (n = 30). Tolerance and ablation success were evaluated at 30 and 90 days and 90 days and 6 months, respectively. Tolerance was defined as stable liver function and absence of increased ascites or worsening portal hypertension. Ablation success was defined as tumor eradication on triple phase contrasted computed tomography (CT).

RESULTS

Patients undergoing IRE had shorter length of stay (p = 0.05) and 90 day readmission rate (p = 0.03) than those undergoing MW ablation. Additionally, IRE was better tolerated than MW ablation at 30 and 90 days. IRE and MW ablation resulted in 6 month success rates of 97% and 100%.

CONCLUSION

Treatment of Child-Pugh B (7/8) HCC with IRE results in equivalent ablation success with improved liver tolerance compared with MW ablation and other ablative modalities.

Irreversible Electroporation (IRE): Standardization of Terminology and Reporting Criteria for Analysis and Comparison

BACKGROUND

Irreversible electroporation (IRE) as newer ablation modality has been introduced and its clinical niche is under investigation. At present just one IRE system has been approved for clinical use and is currently commercially available (NanoKnife® system). In 2014, the International Working Group on Image-Guided Tumor Ablation updated the recommendation about standardization of terms and reporting criteria for image-guided tumor ablation. The IRE method is not covered in detail. But the non-thermal IRE method and the NanoKnife System differ fundamentally from established ablations techniques, especially thermal approaches, e.g. radio frequency ablation (RFA).

MATERIAL/METHODS

As numerous publications on IRE with varying terminology exist so far - with numbers continuously increasing - standardized terms and reporting criteria of IRE are needed urgently. The use of standardized terminology may then allow for a better inter-study comparison of the methodology applied as well as results achieved.

RESULTS

Thus, the main objective of this document is to supplement the updated recommendation for image-guided tumor ablation by outlining a standardized set of terminology for the IRE procedure with the NanoKnife Sytem as well as address essential clinical and technical informations that should be provided when reporting on IRE tumor ablation.

CONCLUSIONS

We emphasize that the usage of all above recommended reporting criteria and terms can make IRE ablation reports comparable and provide treatment transparency to assess the current value of IRE and provide further development.

Bursts of Bipolar Microsecond Pulses Inhibit Tumor Growth

Irreversible electroporation (IRE) is an emerging focal therapy which is demonstrating utility in the treatment of unresectable tumors where thermal ablation techniques are contraindicated. IRE uses ultra-short duration, high-intensity monopolar pulsed electric fields to permanently disrupt cell membranes within a well-defined volume. Though preliminary clinical results for IRE are promising, implementing IRE can be challenging due to the heterogeneous nature of tumor tissue and the unintended induction of muscle contractions. High-frequency IRE (H-FIRE), a new treatment modality which replaces the monopolar IRE pulses with a burst of bipolar pulses, has the potential to resolve these clinical challenges. We explored the pulse-duration space between 250 ns and 100 μs and determined the lethal electric field intensity for specific H-FIRE protocols using a 3D tumor mimic. Murine tumors were exposed to 120 bursts, each energized for 100 μs, containing individual pulses 1, 2, or 5 μs in duration. Tumor growth was significantly inhibited and all protocols were able to achieve complete regressions. The H-FIRE protocol substantially reduces muscle contractions and the therapy can be delivered without the need for a neuromuscular blockade. This work shows the potential for H-FIRE to be used as a focal therapy and merits its investigation in larger pre-clinical models.