An in-vivo evaluation of the multi-channel bioimpedance method in monitoring radiofrequency ablation lesions

There are currently no direct clinical methods to monitor radiofrequency (RF) ablation lesions for cardiac arrhythmias. Conventional circuit impedance (CI) tracks thermal changes to estimate lesion formation but overlooks the reactance component, which reflects cellular capacitance. Its abolition during ablation indicates irreversible membrane loss and may serve as a temperature-independent marker of lesion quality. This study aimed to optimise a novel multi-channel bioimpedance method, previously shown to achieve superior correlations with lesion dimensions compared to CI, and evaluate the performance of reactance relative to resistance using this method. In-vivo experiments were performed in seven pigs, with ablations (30-50 W, 30 s) in the right atrium and both ventricles. Resistance and reactance were recorded before, during, and two minutes after ablation, alongside CI. Following euthanasia, lesions were excised and measured. Linear and logistic models assessed correlations between impedance parameters and lesion depth, width and surface area (all chambers), and transmurality (atrium). The results showed that the optimal channel from the multi-channel bioimpedance system consistently outperformed CI, with R (linear) > 0.9 and R (logistic) > 0.98. Resistance was a more reliable predictor of lesion dimensions than reactance, including post-ablation measurements. Post-ablation impedance had stronger correlations in ventricles with thicker walls, but atrial correlations remained sufficient for accurate lesion monitoring. In summary, the multi-channel bioimpedance method was validated in vivo and demonstrated superior accuracy over conventional impedance measurements. These results support its potential to enhance real-time monitoring of ablation lesion formation, improving both safety and efficacy in clinical electrophysiology practice.