Stabilization of unstable reentrant atrial tachycardias via fractionated continuous electrical activity ablation (CHAOS study).

Introduction. Unstable reentrant atrial tachycardias (ATs) (i.e. those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate. We have tested a strategy to achieve arrhythmia stabilization into mappable stable ATs based on the detection and ablation of rotors. Methods and Results. From May 2017 to December 2019, 97 consecutive patients with reentrant ATs were ablated. Of these, 18 (18.6%) presented unstable circuits and were included. Mapping was performed using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV or Advisor HD Grid). Rotors were subjectively identified as fractionated continuous (or quasi-continuous) electrograms on 1-2 adjacent bipoles of the mapping catheter, without dedicated software. 13 patients (72%) had detectable rotors (median 2 [1–3] rotors per patient); focal ablation achieved conversion into stable AT or sinus rhythm in 12 (92%). In the other 6 patients, sites with spatiotemporal dispersion (i.e. all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted. 17 sites with spatiotemporal dispersion were detected and focally ablated. Globally, and excluding 1 patient with spontaneous AT stabilization, ablation success to stabilize the AT was achieved in 16/17 patients (94.1%). One-year freedom from atrial arrhythmias was similar between patients with unstable and stable ATs (66.7% Vs 65.8%, p=0.946). Conclusion. Most unstable reentrant ATs show detectable rotors, identified as sites with single-bipole fractionated quasi-continuous signals, or spatiotemporal dispersion plus non-continuous fractionation. Ablation of these sites is highly effective to stabilize the AT or convert it into sinus rhythm.