Mapping multi-wavelet reentry without isochrones: an electrogram-guided approach to define substrate distribution.

AIMS: A key mechanism responsible for atrial fibrillation is multi-wavelet reentry (MWR). We have previously demonstrated that ablation in regions of increased circuit density reduces the duration of, and decreases the inducibility of MWR. In this study, we demonstrate a method for identifying local circuit density using electrogram frequency and validated its effectiveness for map-guided ablation in a computer model of MWR. METHODS AND RESULTS: We simulated MWR in tissues with variation of action potential duration and intercellular resistance. Electrograms were calculated using various electrode sizes and configurations. We measured and compared the number of circuits to the tissue activation frequency and electrogram frequency using three recording configurations [unipolar, contact bipolar, orthogonal closed unipolar (OCU)] and two frequency measurements (dominant frequency, centroid frequency). We then used the highest resolution electrogram frequency map (OCU centroid frequency) to guide the placement of lesions to high frequency regions. Map-guided ablation was compared with no ablation and random/blind ablation lesions of equal length. Electrogram frequency correlated with tissue frequency and circuit density as a function of electrode spatial resolution. Map-guided ablation resulted in a significant reduction in MWR duration (142 ± 174 vs. 41 ± 63 s). CONCLUSION: Electrogram frequency correlates with circuit density in MWR provided electrodes have high spatial resolution. Map-guided ablation is superior to no ablation and to blind/random ablation.

Ablation of multi-wavelet re-entry: general principles and in silico analyses.

AIMS: Catheter ablation strategies for treatment of cardiac arrhythmias are quite successful when targeting spatially constrained substrates. Complex, dynamic, and spatially varying substrates, however, pose a significant challenge for ablation, which delivers spatially fixed lesions. We describe tissue excitation using concepts of surface topology which provides a framework for addressing this challenge. The aim of this study was to test the efficacy of mechanism-based ablation strategies in the setting of complex dynamic substrates. METHODS AND RESULTS: We used a computational model of propagation through electrically excitable tissue to test the effects of ablation on excitation patterns of progressively greater complexity, from fixed rotors to multi-wavelet re-entry. Our results indicate that (i) focal ablation at a spiral-wave core does not result in termination; (ii) termination requires linear lesions from the tissue edge to the spiral-wave core; (iii) meandering spiral-waves terminate upon collision with a boundary (linear lesion or tissue edge); (iv) the probability of terminating multi-wavelet re-entry is proportional to the ratio of total boundary length to tissue area; (v) the efficacy of linear lesions varies directly with the regional density of spiral-waves. CONCLUSION: We establish a theoretical framework for re-entrant arrhythmias that explains the requirements for their successful treatment. We demonstrate the inadequacy of focal ablation for spatially fixed spiral-waves. Mechanistically guided principles for ablating multi-wavelet re-entry are provided. The potential to capitalize upon regional heterogeneity of spiral-wave density for improved ablation efficacy is described.