Efficacy of multi-electrode linear irreversible electroporation

Pulsed Field Ablation of the Porcine Ventricle Using a Focal Lattice-Tip Catheter

BACKGROUND

Our understanding of catheter-based pulsed field ablation (PFA) of the ventricular myocardium is limited. We conducted a series of exploratory evaluations of ventricular PFA in swine ventricles.

METHODS

A focal lattice-tip catheter was used to deliver proprietary biphasic monopolar PFA applications to swine ventricles under general anesthesia, with guidance from electroanatomical mapping, fluoroscopy, and intracardiac echocardiography. We conducted experiments to assess the impact of (1) delivery repetition (2×, 3×, or 4×) at each location, (2) epicardial PFA delivery, and (3) confluent areas of shallow healed endocardial scar created by prior PFA (4 weeks earlier) on subsequent endocardial PFA. Additional assessments included PFA optimized for the ventricle, lesion visualization by intracardiac echocardiography imaging, and immunohistochemical insights.

RESULTS

Experiment no. 1: lesions (n=49) were larger with delivery repetition of either 4× or 3× versus 2×: length 17.6±3.9 or 14.2±2.0 versus 12.7±2.0 mm (P<0.01, P=0.22), width 13.4±1.8 or 10.6±1.3 versus 10.5±1.1 mm (P<0.01, P=1.00), and depth 6.1±2.1 or 5.1±1.3 versus 4.2±1.0 mm (P<0.01, P=0.21). Experiment no. 2: epicardial lesions (n=18) were reliably created and comparable to endocardial lesions: length 24.6±9.7 mm (n=5), width 15.6±4.6 mm, and depth 4.5±3.7 mm. Experiment no. 3: PFA (n=16) was able to penetrate to a depth of 4.8 (interquartile range, 4.5-5.4) mm in healthy myocardium versus 5.6 (interquartile range, 3.6-6.6) mm in adjacent healed endocardial scar (P=0.79), suggesting that superficial scar does not significantly impair PFA. Finally, we demonstrate, PFA optimized for the ventricle yielded adequate lesion dimensions, can result in myocardial activation, can be visualized by intracardiac echocardiography, and have unique immunohistochemical characteristics.

CONCLUSIONS

This in vivo evaluation offers insights into the behavior of endocardial or epicardial PFA delivered using the lattice-tip catheter to normal or scarred porcine ventricular myocardium, thereby setting the stage for future clinical studies.

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 Comparative Modeling Study of Thermal Mitigation Strategies in Irreversible Electroporation Treatments

Irreversible electroporation (IRE), also referred to as nonthermal pulsed field ablation (PFA), is an attractive focal ablation modality for solid tumors and cardiac tissue due to its ability to destroy aberrant cells with limited disruption of the underlying tissue architecture. Despite its nonthermal cell death mechanism, application of electrical energy results in Joule heating that, if ignored, can cause undesired thermal injury. Engineered thermal mitigation (TM) technologies including phase change materials (PCMs) and active cooling (AC) have been reported and tested as a potential means to limit thermal damage. However, several variables affect TM performance including the pulsing paradigm, electrode geometry, PCM composition, and chosen active cooling parameters, meaning direct comparisons between approaches are lacking. In this study, we developed a computational model of conventional bipolar and monopolar probes with solid, PCM-filled, or actively cooled cores to simulate clinical IRE treatments in pancreatic tissue. This approach reveals that probes with integrated PCM cores can be tuned to drastically limit thermal damage compared to existing solid probes. Furthermore, actively cooled probes provide additional control over thermal effects within the probe vicinity and can altogether abrogate thermal damage. In practice, such differences in performance must be weighed against the increased time, expense, and effort required for modified probes compared to existing solid probes.