Ablating Myocardium Using Nanosecond Pulsed Electric Fields: Preclinical Assessment of Feasibility, Safety, and Durability.

BACKGROUND: Unlike conventional microsecond pulsed electrical fields that primarily target the cell membranes, nanosecond pulses are thought to primarily electroporate intracellular organelles. We conducted a comprehensive preclinical assessment of catheter-based endocardial nanosecond pulsed field ablation in swine. METHODS: A novel endocardial nanosecond pulsed field ablation system was evaluated in a total of 25 swine. Using either a low-dose (5-second duration) or high-dose (15-second duration) strategy, thoracic veins and discrete atrial and ventricular sites were ablated. Swine survived for <1 (n=1), ≈2 (n=7), ≈7 (n=6), 14 (n=2), or ≈28 (n=9) days, and venous isolation was assessed before euthanize. Safety assessments included evaluation of esophageal effects, phrenic nerve function, and changes in venous caliber. All tissues were subject to careful gross pathological and histopathologic examination. RESULTS: All (100%) veins (13 low-dose, 34 high-dose) were acutely isolated, and all reassessed veins (6 low-dose, 15 high-dose) were durably isolated. All examined vein lesions (10 low-dose, 22 high-dose) were transmural. Vein diameters (n=15) were not significantly changed. Of the animals assessed for phrenic palsy (n=9), 3 (33%) demonstrated only transient palsy. There were no differences between dosing strategies. Thirteen mitral isthmus lesions were analyzed, and all 13 (100%) were transmural (depth, 6.4±0.4 mm). Ventricular lesions were 14.7±4.5 mm wide and 7.1±1.3 mm deep, with high-dose lesions deeper than low-dose (7.9±1.2 versus 6.2±0.8 mm; P=0.007). The esophagus revealed nontransmural adventitial surface lesions in 5 of 5 (100%) animals euthanized early (2 days) post-ablation. In the 10 animals euthanized later (14-28 days), all animals demonstrated significant esophageal healing-8 with complete resolution, and 2 with only trace fibrosis. CONCLUSIONS: A novel, endocardial nanosecond pulsed field ablation system provides acute and durable venous isolation and linear lesions. Transient phrenic injury and nontransmural esophageal lesions can occur with worst-case assessments suggesting limits to pulsed field ablation tissue selectivity and the need for dedicated assessments during clinical studies.

Effects of Pulsed Electric Fields on the Coronary Arteries in Swine.

BACKGROUND: Previous animal studies have shown no significant vascular injury from pulsed electrical field (PEF) ablation. We sought to assess the effect of PEF on swine coronary arteries. METHODS: We performed intracoronary and epicardial (near the coronary artery) PEF ablations in swine pretreated with dual antiplatelet and antiarrhythmic therapy. Intracoronary PEF was delivered using MapiT catheters (Biotronik, Berlin), whereas epicardial PEF was delivered using EPT catheters (Boston Scientific, MA). PEF pulse duration was microseconds (Nanoknife 3.0, Angio Dynamics, NY) or nanoseconds (CellFX, Pulse Biosciences, CA). RESULTS: We performed 39 intracoronary ablations in 10 swine and 20 epicardial-pericoronary ablations in 4 separate swine. Intracoronary PEF was delivered at higher energy compared with epicardial PEF (46 [interquartile range, IQR 20-85] J versus 10 [IQR 10-11] J, P < 0.01). Reversible coronary spasm occurred in 49% intracoronary ablations and 45% epicardial ablations (P=0.80). At the end study, fixed coronary stenosis was demonstrated in 44% intracoronary ablations (80% for microsecond PEF and 18% for nanosecond PEF) and 0% epicardial ablations. Visible hemorrhagic and/or fibrotic myocardial lesions were observed at necropsy with similar frequency between intracoronary and epicardial PEF (45% versus 50%, P=0.70). Nanosecond PEF (49 ablations in 11 swine), when compared with microsecond PEF (10 intracoronary ablations in 3 swine), resulted in lower energy delivery (21 [IQR 10-46] J versus 129 [IQR 24-143] J, P=0.03) and less incidence of fixed coronary stenosis (18% versus 80%, P=0.04). CONCLUSIONS: In the swine model, intracoronary PEF resulted both in significant coronary spasm and fixed coronary stenosis. Epicardial PEF, delivered at lower energy, resulted in reversible spasm but no fixed coronary stenosis.

Ventricular nanosecond pulsed electric field delivery using active fixation leads: a proof-of-concept preclinical study.

BACKGROUND: Mid-myocardial ventricular arrhythmias are challenging to treat. Cardiac electroporation via pulsed electric fields (PEFs) offers significant promise. We therefore tested PEF delivery using screw-in pacemaker leads as proof-of-concept. METHODS: In 5 canine models, we applied nanosecond PEF (pulse width 300 ns) across the right ventricular (RV) septum using a single lead bipolar configuration (n = 2) and between two leads (n = 3). We recorded electrograms (EGMs) prior to, immediately post, and 5 min after PEF. Cardiac magnetic resonance imaging (cMRI) and histopathology were performed at 2 weeks and 1 month. RESULTS: Nanosecond PEF induced minimal extracardiac stimulation and frequent ventricular ectopy that terminated post-treatment; no canines died with PEF delivery. With 1 lead, energy delivery ranged from 0.64 to 7.28 J. Transient ST elevations were seen post-PEF. No myocardial delayed enhancement (MDE) was seen on cMRI. No lesions were noted on the RV septum at autopsy. With 2 leads, energy delivery ranged from 56.3 to 144.9 J. Persistent ST elevations and marked EGM amplitude decreases developed post-PEF. MDE was seen along the septum 2 weeks and 1 month post-PEF. There were discrete fibrotic lesions along the septum; pathology revealed dense connective tissue with < 5% residual cardiomyocytes. CONCLUSIONS: Ventricular electroporation is feasible and safe with an active fixation device. Reversible changes were seen with lower energy PEF delivery, whereas durable lesions were created at higher energies. Central illustration: pulsed electric field delivery into ventricular myocardium with active fixation leads.

A dose-response study of nanosecond electric energy pulses on facial skin.

Nanosecond pulsed electric fields, also known as Nano-Pulse Stimulation or NPS, can trigger regulated cell death to clear skin lesions that are cellular in nature. Before treating facial lesions, it is important to demonstrate the effects of these pulses on normal facial skin. Here we have applied a range of NPS energies to the epidermis and dermis of normal facial skin scheduled for excision to establish a safe dose range of energies prior to use in clinical applications. This was an open-label, non-randomized study under the direction of a single Principal Investigator. The time course of the treated tissue changes was determined by histological analysis. All energy settings generated a delayed epidermal loss followed by re-epithelialization by day 7 and a normal course of healing. One day after NPS treatment, the cellular membranes of the treated epidermis were intact, but their nuclei no longer stained with H&E, resulting in a hollow appearance that has been referred to as "ghost cells." Cellular structures in the dermis, such as sebaceous glands and melanocytes, exhibited regulated cell death observed by 1 day post treatment. Melanocytes recovered to their normal density within 7 days. The 60-day samples indicated that epidermis, hair follicles, and eccrine glands appeared normal. The selective effect of NPS treatment on cellular structures in the epidermal and dermal layers suggests that this non-thermal modality of energy delivery is ideal for treating cellular targets including benign and malignant skin lesions. NPS skin treatments provide a promising method for clearing skin lesions with a cellular basis.

A dose-response study of a novel method of selective tissue modification of cellular structures in the skin with nanosecond pulsed electric fields.

BACKGROUND AND OBJECTIVES: This study describes the effects of nanosecond pulsed electric fields (nsPEF) on the epidermis and dermis of normal skin scheduled for excision in a subsequent abdominoplasty. NsPEF therapy applies nanosecond pulses of electrical energy to induce regulated cell death (RCD) in cellular structures, with negligible thermal effects. Prior pre-clinical studies using nsPEF technology have demonstrated the ability to stimulate a lasting immune response in animal tumor models, including melanoma. This first-in-human-use of nsPEF treatment in a controlled study to evaluate the dose-response effects on normal skin and subcutaneous structures is intended to establish a safe dose range of energies prior to use in clinical applications using nsPEF for non-thermal tissue modification. STUDY DESIGN/MATERIALS AND METHODS: Seven subjects with healthy tissue planned for abdominoplasty excision were enrolled. Five subjects were evaluated in a longitudinal, 60-day study of effects with doses of six nsPEF energy levels. A total of 30 squares of spot sizes 25mm2 or less within the planned excision area were treated and then evaluated at 1 day, 5 days, 15 days, 30 days, and 60 days prior to surgery. Photographs were taken over time of each treated area and assessed by three independent and blinded dermatologists for erythema, flaking and crusting using a 5-point scale (0 = low, 4 = high). Punch biopsies of surgically removed tissue were processed and evaluated for tissue changes using hematoxylin and eosin, trichome, caspase-3, microphthalmia transcription factor, and elastin stains and evaluated by a dermatopathologist. The skin of two subjects received additional treatments at 2 and 4 hours post-nsPEF and was evaluated in a similar manner. RESULTS: Most energy settings exhibited delayed epidermal loss followed by re-epithelization by day 15 and a normal course of healing. Histologic analysis identified the appearance of activated caspase-3 at two and four hours after nsPEF treatment, but not at later time points. At the 1-day time point, a nucleolysis effect was observed in epidermal cells, as evidenced by the lack of nuclear staining while the epidermal plasma membranes were still intact. Cellular structures within the treatment zone such as melanocytes, sebaceous glands, and hair follicles were damaged while acellular structures such as elastic fibers and collagen were largely unaffected except for TL6 which showed signs of dermal damage. Melanocytes reappeared at levels comparable with untreated controls within 1 month of nsPEF treatment. CONCLUSIONS: The selective effect of nsPEF treatment on cellular structures in the epidermal and dermal layers suggests that this non-thermal mechanism for targeting cellular structures does not affect the integrity of dermal tissue within a range of energy levels. The specificity of effects and a favorable healing response makes nsPEF ideal for treating cellular targets in the epidermal or dermal layers of the skin, including treatment of benign and malignant lesions. NsPEF skin treatments provide a promising, non-thermal method for treating skin conditions and removing epidermal lesions. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Safety and Efficacy of Nanosecond Pulsed Electric Field Treatment of Seborrheic Keratoses.

BACKGROUND: Nanosecond pulsed electric field technology (also known as Nano-Pulse Stimulation or NPS) is a nonthermal, drug-free, energy-based technology that has demonstrated effects on cellular structures of the dermis and epidermis in previous clinical studies. OBJECTIVE: To evaluate the safety and efficacy of a single NPS treatment for clearing seborrheic keratoses (SKs). MATERIALS AND METHODS: This study was a prospective, randomized, open-label, multisite, nonsignificant risk trial in which each subject served as their own control. Fifty-eight subjects had 3 of 4 confirmed SK lesions treated, resulting in 174 total treated lesions. Subjects returned for 5 to 6 follow-up evaluations and photographs. RESULTS: At 106 days after NPS treatment, 82% of treated seborrheic keratoses were rated clear or mostly clear by the assessing physician. Seventy-one percent of lesions were rated clear or mostly clear by the 3 independent reviewers based on the 106-day photographs. All treated subjects returned for all study visits, and 78% of the subjects were satisfied or mostly satisfied with the outcome of the treatment. No adverse events were reported. CONCLUSION: The NPS procedure was well tolerated and effective in the removal of SKs.

Safety and Efficacy of Nanosecond Pulsed Electric Field Treatment of Sebaceous Gland Hyperplasia.

BACKGROUND: Nanosecond pulsed electric field (nsPEF) technology involves delivery of ultrashort pulses of electrical energy and is a nonthermal, drug-free technology that has demonstrated favorable effects on cellular structures of the dermis and epidermis. OBJECTIVE: Determine the tolerability and effectiveness of nsPEF treatment of sebaceous gland hyperplasia (SGH). METHODS: This study was a prospective, randomized, open-label, multisite, nonsignificant risk trial in which each subject served as their own control. After injection of local anesthetic, high-intensity, ultrashort pulses of electrical energy were used to treat 72 subjects resulting in a total of 222 treated lesions. Subjects returned for 3 to 4 follow-up evaluations with photographs. RESULTS: At the final study visit, 99.6% of treated SGH lesions were rated clear or mostly clear and 79.3% of the subjects were satisfied or mostly satisfied with the outcome. At 60 days after nsPEF treatment, 55% of the lesions were judged to have no hyperpigmentation and 31% exhibited mild post-treatment hyperpigmentation. At the last observation for all lesions, 32% of the 222 lesions were noted as having slight volume loss. CONCLUSION: Nanosecond pulsed electric field procedure is well tolerated and is very effective in the removal of SGHs. TRIAL REGISTRATION: ClinicalTrials.gov NCT03612570.

Nano-Pulse Stimulation is a physical modality that can trigger immunogenic tumor cell death.

BACKGROUND: We have been developing a non-thermal, drug-free tumor therapy called Nano-Pulse Stimulation (NPS) that delivers ultrashort electric pulses to tumor cells which eliminates the tumor and inhibits secondary tumor growth. We hypothesized that the mechanism for inhibiting secondary tumor growth involves stimulating an adaptive immune response via an immunogenic form of apoptosis, commonly known as immunogenic cell death (ICD). ICD is characterized by the emission of danger-associated molecular patterns (DAMPs) that serve to recruit immune cells to the site of the tumor. Here we present evidence that NPS stimulates both caspase 3/7 activation indicative of apoptosis, as well as the emission of three critical DAMPs: ecto-calreticulin (CRT), ATP and HMGB1. METHODS: After treating three separate cancer cell lines (MCA205, McA-RH7777, Jurkat E6-1) with NPS, cells were incubated at 37 °C. Cell-culture supernatants were collected after three-hours to measure for activated caspases 3/7 and after 24 h to measure CRT, ATP and HMGB1 levels. We measured the changes in caspase-3 activation with Caspase-Glo® by Promega, ecto-CRT with anti-CRT antibody and flow cytometry, ATP by luciferase light generation and HMGB1 by ELISA. RESULTS: The initiation of apoptosis in cultured cells is greatest at 15 kV/cm and requires 50 A/cm2. Reducing this current inhibits cell death. Activated caspase-3 increases 8-fold in Jurkat E6-1 cells and 40% in rat hepatocellular carcinoma and mouse fibrosarcoma cells by 3 h post treatment. This increase is non-linear and peaks at 15-20 J/mL for all field strengths. 10 and 30 kV/cm fields exhibited the lowest response and the 12 and 15 kV/cm fields stimulated the largest amount of caspase activation. We measured the three DAMPs 24 h after treatment. The expression of cell surface CRT increased in an energy-dependent manner in the NPS treated samples. Expression levels reached or exceeded the expression levels in the majority of the anthracycline-treated samples at energies between 25 and 50 J/mL. Similar to the caspase response at 3 h, secreted ATP peaked at 15 J/mL and then rapidly declined at 25 J/mL. HMGB1 release increased as treatment energy increased and reached levels comparable to the anthracycline-treated groups between 10 and 25 J/mL. CONCLUSION: Nano-Pulse Stimulation treatment at specific energies was able to trigger the emission of three key DAMPs at levels comparable to Doxorubicin and Mitoxantrone, two known inducers of immunogenic cell death (ICD). Therefore NPS is a physical modality that can trigger immunogenic cell death in tumor cells.