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Pulse electric fields (PEF) are being investigated as an alternative ablation modality to traditional radiofrequency ablation for modification of myocardial substrate.
Objective
Assess the extent and time course of myocardial scar formation caused by application of PEF at the interventricular septum.
Methods
Four-week survival experiments were performed in 8 canines. Energy was delivered using ablation catheters in bipolar configuration to apply PEF to the septum. Two animals were administered pulses at microsecond pulse widths and six received nanosecond pulses for a total 75-189 J delivered per animal. MRI studies were performed in 4 of the 8 animals. Scar formation was assessed by measuring late gadolinium enhancement (LGE) and confirmed by histology.
Results
Sites of PEF delivery exhibited myocardial edema on triple inversion recovery and early scar with some LGE visible after 7 days. Lesion volumes were larger for transmural configurations vs. bipolar PEF delivered in a single cardiac chamber (10.7 ± 2.3 cm3 vs. 2.9 ± 1.1 cm3). At 30 days, lesions predominantly exhibited LGE and total lesion volumes were similar for both groups (5.3 ± 2.4 cm3 vs. 4.0 ± 0.2 cm3). Transmural MRI lesions were achieved when bipolar electrodes were placed on either side of the septum, and total lesion volume was dose-dependent. Myocardial fibrosis was identified on histology. Bipolar configurations entirely within a chamber produced superficial lesions, even with delivery of higher energy.
Conclusion
Application of PEF to the myocardium can cause substrate modification, including transmural fibrosis. Lesion volume is dose-dependent for transmural electrode configurations.
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