Pulsed field ablation and ventricular capture: assessing the need for R-wave gated therapy

Abstract

Abstract Background Pulsed field ablation (PFA) is a therapy that disrupts cellular homeostasis by applying high intensity and short duration electrical pulses to cardiac tissue, ultimately resulting in cell death. Such stimuli have the potential to initiate ventricular arrhythmias if the therapy is not synchronized with the beginning of ventricular systole (R-wave gating). For the treatment of cardiac arrhythmias, it is important that the candidate therapy locations in the left atrium (e.g., pulmonary veins) are a sufficient distance away from ventricular tissue to avoid ventricular capture. Objective data exploring the need for R wave gating in the context of PFA therapy for pulmonary vein isolation is currently lacking. Purpose To study the effect of electrode distance of the 12-electrode loop catheter from the epicardium on likelihood of ventricular capture. Methods A sternotomy was performed on swine to expose the heart. An incision was then made in the pericardial sac and the edges were lifted and sutured to the surrounding chest cavity to create a cradle. The function of the cradle was to hold a ∼37C saline solution (tuned to match the electrical conductivity of blood) while PFA treatments were performed. Two left ventricular sites (apex and lateral aspect) were selected for treatment, taking care to avoid proximity to the coronary artery. For each PFA therapy trial, the catheter loop was positioned 10mm above the surface of the epicardium and then advanced in 1mm increments until capture was achieved; spacers were used to assure fixed spacing during cardiac activity. For each trial, the maximum distance between the catheter and the epicardium at which the IRE therapy captured the ventricle was recorded. Additionally, CT scans (N=20 human patients) were analyzed to understand distances of interest to ventricular tissue. Results N=12 trials were conducted at each target in each animal (N=48 total ablations). For all trials, the minimum capture distance was found to be 6-8mm (4/48 at 6mm, 28/48 at 7mm and 16/48 at 8mm), with a mean capture distance of 7.25±0.60mm. The mean capture distances for the left ventricular apex and lateral aspect were 7.29±0.55mm and 7.21±0.66mm, respectively (p=0.636). For the CT scan analysis, the minimum distance from pulmonary vein ostia to left ventricular tissue ("nominal case") were 10.6mm and 12.8mm for the left superior and inferior veins, respectively. Considering the use ("worst case") where the catheter is placed just distal to the ostia, the distances to ventricular tissue were 1.6mm and 5.8mm, respectively; 4/20 patients had a vein less than 10mm from ventricular myocardium. Conclusions This study was successful in establishing the distance of ventricular capture via PFA therapy (6-8mm for the considered therapy). Given the described use and CT analysis, there is potential risk in triggering ventricular arrhythmia via PFA therapy unless R-wave triggering is implemented.