Pulsed-field ablation: Computational modeling of electric fields for lesion depth analysis

Abstract

Background: Pulsed-field ablation (PFA) is an emerging and promising nonthermal technology for cardiac ablation. The effective applied voltage to achieve adequate irreversible myocardial injury is not well studied. The pulsed-field strength remains independent of tissue contact; therefore, PFA is assumed to be an ablation technology, not mandating the need for tissue contact.

Objective: Determine the effect of applied voltage and distance to surface on depth of myocardial injury using PFA.

Methods: A computational model was developed and validated based on extracted data from in vivo studies to examine the effect of different applied voltages and the impact of distance between the catheter and endocardial surface on the depth of irreversible myocardial injury using PFA.

Results: The depth of lesions created by PFA are dose-dependent, and there is a direct correlation between applied PFA voltages and depth of irreversible myocardial injury. The minimum applied voltage of PFA required to create a lesion deeper than 1 mm is 300 volts. The catheter-tissue contact plays a pivotal role in determining lesion depth. With optimal catheter contact in the absence of trabeculation, the minimal applied energy required to achieve a 3-mm-deep lesion is 700 volts. A minor increase in the catheter-tissue distance of 1-2 mm doubles the minimum required applied voltage, increasing it to 1500 volts.

Conclusion: PFA is an important new technology that is proposed to be more efficacious and safer than currently used thermal ablation. Here we demonstrate the impact of dose dependence and the need for maintaining tissue contact during ablation.

Keywords: Catheter ablation; Irreversible electroporation; PFA doses; Pulsed-field ablation; Tissue contact.

Graphical abstract

Figure 1

Computer model validation results. Validation results were obtained from available literature reporting lesion depth due to pulsed-field ablation delivery in porcine models. The graph assumes an irreversible electroporation threshold of 268 V/cm for the in vivo data. The computer model has a 1% and 5% error with Stewart and colleagues and Koruth and colleagues, respectively.

Figure 2

Electric field depths are evaluated under varying voltage loads. From 100 to 2500 V, the electric field strength (V/cm) is measured in the heart muscle, moving away from the electrodes. An irreversible electroporation (IRE) threshold is provided to estimate the boundary of irreversible and reversible electroporation.

Figure 3

Electric field maps having a 700 volt load. The top complete models are presented in a dimetric orientation, having an electric field map plotted along the frontal plane running through the central axis of the electrodes as well as an electric field map plotted along a sagittal plane through the left electrode. The partial bottom models show the electric field map plotted on the frontal plane of the heart tissue alone. Electrodes are shown at adequate tissue contact and then raised above the tissue surface at 1-mm intervals from 1 to 5 mm from right to left.

Figure 4

Electric field maps having a 1200 volt load. The top complete models are presented in a dimetric orientation, having an electric field map plotted along the frontal plane running through the central axis of the electrodes as well as an electric field map plotted along a sagittal plane through the left electrode. The partial bottom models show the electric field map plotted on the frontal plane of the heart tissue alone. Electrodes are shown at adequate tissue contact and then raised above the tissue surface at 1-mm intervals from 1 to 5 mm from right to left.

Figure 5

Electric field depth due to poor electrode-tissue contact. Electrodes are elevated above the tissue at 1-mm intervals from 1 to 5 mm above the tissue. The following voltages are evaluated under the above conditions: A: 100 V, B: 500 V, C: 1000 V, D: 1500 V, E: 2000 V, and F: 2500 V. An irreversible electroporation (IRE) threshold is given to estimate potential pulsed-field ablation lesion depths.