High-frequency irreversible electroporation for cardiac ablation using an asymmetrical waveform

Abstract

Background: Irreversible electroporation (IRE) using direct current (DC) is an effective method for the ablation of cardiac tissue. A major drawback of the use of DC-IRE, however, are two problems: requirement of general anesthesia due to severe muscle contractions and the formation of bubbles containing gaseous products from electrolysis. The use of high-frequency alternating current (HF-IRE) is expected to solve both problems, because HF-IRE produces little to no muscle spasms and does not cause electrolysis.

Methods: In the present study, we introduce a novel asymmetric, high-frequency (aHF) waveform for HF-IRE and present the results of a first, small, animal study to test its efficacy.

Results: The data of the experiments suggest that the aHF waveform creates significantly deeper lesions than a symmetric HF waveform of the same energy and frequency (p = 0.003).

Conclusion: We therefore conclude that the use of the aHF enhances the feasibility of the HF-IRE method.

Conflict of interest statement

The authors declare that they have no competing interests. Part of this research has been funded by Abbott Laboratories, Abbott Park, Illinois, USA. A patent concerning the asymmetric waveform has been filed (ownership: Abbott, Illinois, USA. Inventor: Maurits K Konings).

Figures

Fig. 1

Schematics, showing a single wave period of a symmetric and an asymmetric waveform, having the same energy and the same time duration T of a single wave period. a Single wave period of a “symmetric waveform”. b Single wave period showing an adapted waveform in which the negative phase is flattened and spread out, while the positive phase is narrowed and higher (“asymmetric waveform”). The parameter β indicates the ratio of the duration of the long phase to the duration of the short phase

Fig. 2

a The used suction cup electrode showing the 42 × 7 mm suction cup (I) connected to a vacuum system (II), containing a 35 × 6 mm stainless steel electrode (III) that is connected to the HF generator by a cable (IV). b Placement of the suction cup electrode on the right ventricle. LV left ventricle, RV right ventricle

Fig. 3

Current strength (in amperes) produced in the experiments of model M, as function of time in microseconds. a Symmetrical waveform. b Asymmetrical waveform

Fig. 4

Lesion depth of the symmetrical and asymmetrical HF ablations in model M (n = 5). The black lines indicate the paired measurements; red lines indicate the mean and standard deviation per group

Fig. 5

Graphical rendering of the role of the parameters β and G in the asymmetrical waveform

Fig. 6

Plot of Qa/Qs as function of β. For all values of β > 1, the ratio Qa/Qs < 1, which implies that Qa will always be smaller than Qs if β ≠ 1