Feasibility of unipolar signal-guided ablation in creating contiguous lines of conduction block: A proof-of-concept study.

BACKGROUND

Modification of the atrial unipolar electrogram (Uni-EGM) with loss of the near-field negative component in response to radiofrequency (RF) ablation reflects transmural loss of tissue conductivity.

OBJECTIVE

This study sought to investigate the feasibility of Uni-EGM morphology-guided RF ablation in generating contiguous, transmural lesions that result in conduction block. This method was compared with ablation guided by standard ablation index parameters.

METHODS

In a beating heart swine model, linear transcaval ablation was performed using an irrigated ablation catheter with standard and high-power RF ablation. First, an optimal Uni-EGM endpoint for predicting a transmural lesion was determined by single RF applications in the smooth and trabeculated portions of the right atrium. We compared termination of RF energy immediately upon observing consistent loss of the negative component (S wave) on the local Uni-EGM vs extending RF delivery for an additional 3 seconds beyond (U+3). Next, linear ablation was achieved with either target ablation index of 400 or Uni-EGM (U+3)-based techniques. The latter method relied upon Uni-EGM morphology both to direct catheter positioning at sites of contiguous and viable tissue and to titrate RF delivery. Bidirectional block was demonstrated with standard EP pacing maneuvers, high-density activation mapping, and pathology.

RESULTS

Extending RF delivery for 3 additional seconds (U+3) after consistent loss of the negative component on the Uni-EGM proved an optimal endpoint, predicting a transmural lesion with 94% sensitivity and 100% specificity. It was observed that, with increasing distance from site of RF application, the near-field S wave on the Uni-EGM grows in magnitude whereas an acute current of injury pattern diminishes. Uni-EGM-based technique resulted in equal efficacy in producing ablation lines with complete bidirectional block compared with target AI-guided ablation. With standard power, Uni-EGM-guided ablation resulted in significantly less energy delivered per RF application.

CONCLUSION

We demonstrate that Uni-EGM can successfully guide ablation yielding conduction lines of block. Uni-EGM morphology reflects local tissue activation, and its modification in response to thermal injury can serve as an endpoint to ensure adequate yet avoid excess RF delivery. The near-field S wave on the Uni-EGM indicates viable tissue and, in conjunction with an acute current of injury, identified contiguous, conductive tissue for targeting. Characterization of Uni-EGM morphology with respect to myocardial electrical properties and understanding its modification in response to injury may lend to the continued pursuit of safer, more effective ablation strategies.