OBJECTIVE
Irreversible electroporation is a nonthermal ablative tool that uses direct electrical pulses to create irreversible membrane pores and cell death. The ablation zone is surrounded by a zone of reversibly increased permeability; either zone can cause cardiac arrhythmias. Our purpose was to establish a safety profile for the use of irreversible electroporation close to the heart.
MATERIALS and METHODS
The effect of unsynchronized and synchronized (with the R wave on ECG) irreversible electroporation in swine lung and myocardium was studied in 11 pigs. Twelve lead ECG recordings were analyzed by an electrophysiologist for the presence of arrhythmia. Ventricular arrhythmias were categorized as major events. Minor events included all other dysrhythmias or ECG changes. Cardiac and lung tissue was submitted for histopathologic analysis. Electrical field modeling was performed to predict the distance from the applicators over which cells show electroporation-induced increased permeability.
RESULTS
At less than or equal to 1.7 cm from the heart, fatal (major) events occurred with all unsynchronized irreversible electroporation. No major and three minor events were seen with synchronized irreversible electroporation. At more than 1.7 cm from the heart, two minor events occurred with only unsynchronized irreversible electroporation. Electrical field modeling correlates well with the clinical results, revealing increased cell membrane permeability up to 1.7 cm away from the applicators. Complete lung ablation without intervening live cells was seen. No myocardial injury was seen.
CONCLUSION
Unsynchronized irreversible electroporation close to the heart can cause fatal ventricular arrhythmias. Synchronizing irreversible electroporation pulse delivery with absolute refractory period avoids significant cardiac arrhythmias.
IRE has the potential to damage nerves and may result in axonal swelling, fragmentation, and distal Wallerian degeneration. However, preservation of endoneurium architecture and proliferation of Schwann cells may suggest the potential for axonal regeneration. In contrast, RFA leads to thermal nerve damage, causing protein denaturation, and suggests a much lower potential for regeneration.
Juvenile dispersal and the exchange of offspring among fish populations in river–tributary networks are difficult to characterize, but they may play a substantial role in the dynamics of fisheries in these systems. We used geochemical signatures in otoliths to identify the natal origins of young‐of‐year smallmouth bass Micropterus dolomieu in the James River and a tributary, the Maury River, in Virginia. The trace element signatures (Sr:Ca, Rb:Ca, Mg:Ca, and Ba:Ca) in otoliths differed significantly between these two rivers, resulting in approximately 87% accuracy in classifying known‐origin fry to their natal rivers. The variation in otolith composition reflected the variation in water chemistry within the system. We subsequently used classification functions and stock mixture analyses based on these signatures to identify the natal origins of age‐1 juveniles collected from the same rivers 1 year later. The results indicate that approximately 50% of the age‐1 smallmouth bass collected in the James River were spawned in the Maury River, while no evidence for reciprocal main stem‐to‐tributary exchange was found. These results suggest that the downstream movement and dispersal of smallmouth bass is common in their first year of life. Such inputs from tributaries may play an important role in the dynamics of smallmouth bass river fisheries, which are often characterized by substantial annual variation in recruitment. Characterizing such exchange at broader scales will probably be an important step toward linking the spatial ecology of this species with effective management and conservation strategies in river–tributary networks.
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