Abstract
BackgroundAblation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart.MethodsWe developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium (“penetrating needles” configuration) and one circular electrode each on epi- and endocardium, opposing each other (“epi-endo” configuration).ResultsFor thick tissues (10 mm) and moderate anisotropy ratio (a = 2), we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10) leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration.For thinner tissues (4 mm, typical for human atria) and higher anisotropy ratio (a = 10), the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist.ConclusionsThese results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the fiber orientation is not consistent across the atrial wall.
Highlights
Ablation of cardiac tissue is an important treatment of cardiac arrhythmias, especially atrial fibrillation [1, 2]
We developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue
We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated
Summary
Ablation of cardiac tissue is an important treatment of cardiac arrhythmias, especially atrial fibrillation [1, 2]. Ablation via membrane permeabilization, induced by pulsed electric fields, is an interesting alternative that has successfully been used in tumors [9] and more recently in the heart [10,11,12,13]. An interesting question is whether pulsed electric field ablation produces lesions of a geometry that is more likely to avoid recurrence. To predict the geometry of the ablated volume, we develop a model that allows us to compute the electric field distribution inside the myocardium. We validate the model by comparing predicted to experimentally determined ablation volumes and identify the critical field needed for ablation of cardiac tissue for a particular set of shock parameters. Ablation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart
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