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

There are currently no direct methods to monitor radiofrequency (RF) ablation lesions for cardiac arrhythmias that can be applied in the clinical setting. Recent ex-vivo experiments revealed the impact of the reactance component in bioimpedance on detecting tissue necrosis, with minimal influence from temperature. The objective of this study was to further optimise a novel multi-channel bioimpedance method which has previously demonstrated superior correlations with lesion dimensions compared to conventional circuit impedance. In-vivo experiments were designed to test the multi-channel bioimpedance at full capacity, with both resistance and reactance components recorded before, during, and 2 minutes into post-ablation, with comparison to the circuit impedance. 7 pigs underwent RF ablations at 30-50W and 30 seconds in the right atrium, and left and right ventricle, followed by euthanasia, heart explantation and evaluation of lesion measurements. Linear and logistic models were used to evaluate the impedance correlation with lesion depth and surface area, and in distinguishing lesion transmurality. This study demonstrated that the optimal channel from the multi-channel bioimpedance outperformed the circuit impedance in all tests, with R (linear) > 0.9 and R (logistic) > 0.98. The resistance component was a superior indicator of lesion dimensions than the reactance, even in the post-ablation period. Finally, while post-ablation impedance measurements showed better correlation for lesion monitoring in the ventricles (thicker wall), ablation correlation was sufficient in the atrium (thinner wall) to allow accurate monitoring of lesion dimensions. In conclusion, the multi-channel bioimpedance was tested in vivo and achieved sufficient correlation to improve the safety and efficacy of lesion monitoring in the clinical setting.