A novel bioimpedance mapping system to assess ablation lesion quality and transmurality

Introduction Cardiac catheter ablation is a major solution for treating arrhythmias with steadily growing annual cases. However, 33% of patients with atrial fibrillation [1] and 46.4% with cardiomyopathy-induced ventricular arrhythmias [2,3] required repeated ablation due to insufficient ablation lesions, leading to circuit reconnections and conditions for disease progression. Poor lesion assessment is a significant roadblock due to relying solely on surrogate parameters (electrograms, contact force, and temperature), which significantly limit procedure efficacy [4]. Purpose This study introduced a novel bioimpedance mapping method, LesioLogic, with validation results on large animal models to assess lesion dimension and transmurality, providing real-time feedback for electrophysiologists to maximise lesion creation, thereby improving first-procedure success. Method Seven female landrace pigs underwent anatomical mapping by CARTO3 system and Decanav mapping catheter to map the right atrium (RA), right ventricle (RV) and left ventricle (LV), followed by bioimpedance measurements and radiofrequency (RF) ablation using a 8-F, 3.5 mm Thermocool SmartTouch SF ablation catheter. The ablations were performed at 30-50W for 30 seconds and at 12ml/min irrgation rate. LesioLogic (Figure 1A) utilised 28 pairs of surface electrodes and the catheter electrodes to measure lesions' impedances (50kHz) in multiple directions. The conventional circuit impedance was concomitantly measured between the catheter tip and return pad for comparison. The bioimpedances were measured pre- and post-ablation (immediately and 2 minutes in), and gated to the cardiac and respiratory cycle (Figure 1B). The heart was explanted from euthanised animal for assessing lesion depths and surface areas (SAs) and trasmurality in correlation to the final impedance changes using linear and logistic mixed-effect models. Results 44 lesions were created (LV: 15, RV: 14, RA: 14 - six transmural, Figure 1C) with depths of 3.9±1.1, 3.5±1.4, and 1.5±1.2 mm and surface areas of 34.6±13.6, 31.8±16.2, and 7.3±7.6 mm² respectively. Compared to circuit impedance, LesioLogic demonstrated superior correlations to both lesion parameters in LV and RV (best R = 0.91 vs. 0.67 - depth, 0.89 vs. 0.74 - SA, Figure 2A,B) and exceptional transmurality detection (R = 0.98 vs. 0.72) (Figure 2C). Within LesioLogic, two-minute post-ablation bioimpedances performed better in LV and RV (thicker muscles), while immediate post-ablation measurements sufficed for RA. Conclusions LesioLogic has demonstrated its capability to provide critical yet absent assessment of lesion creation with reliability and high accuracy to leverage procedure efficacy, improve patient outcomes and reduce repeated ablation. The system is currently validated with pulsed-fied ablation and in characterising scar substrates/ventricular tachycardia detection for infarct patients.Figure 1.Experiment set upFigure 2.Novel bioimpedance results