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

Abstract Funding Acknowledgements Type of funding sources: None. Background. Unstable reentrant atrial tachycardias (ATs) (i.e. those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate.  Purpose. We have tested a strategy to convert unstable reentrant ATs into mappable stable ATs based on the detection and ablation of rotors. Methods. From May 2017 to December 2019, we included all consecutive patients scheduled for ablation of reentrant AT, excluding CTI-dependent atrial flutter, in which the tachycardia circuit was unstable. Operators subjectively identified rotors as sites with fractionated continuous (or quasi-continuous) electrical signals on 1-2 adjacent bipoles of conventional high-density mapping catheters, without dedicated software (Figure, A). Focal ablation of these sites was performed in order to stabilize the AT or convert it into sinus rhythm. In patients without rotors or failed rotor ablation, sites with spatiotemporal dispersion (i.e. all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted (Figure, B). Procedural success was defined as the successful ablation of all inducible ATs, without need of cardioversion, final sinus rhythm and non-inducibility. Follow-up included visits with ECG and 24h Holter-ECG at 3, 6 and 12 months. Results. From May 2017 to December 2019, 97 patients were scheduled for reentrant AT ablation, excluding CTI-dependent atrial flutter. Of these, 18 patients (18.6%; 72.1 ± 8.9 years of age, 9 females) presented unstable circuits and were included. 9 patients (50%) had structural cardiomyopathy, 11 patients (61%) prior atrial arrhythmias ablations, and 4 patients (22%) previous cardiac surgery. 13 patients (72%) had detectable rotors (26 rotors; median 2 [1–3] rotors per patient); focal ablation achieved conversion into stable AT or sinus rhythm in 12 (92%). In the other patient, and the 5 patients without detectable rotors, 17 sites with spatiotemporal dispersion were detected and focally ablated, with success to achieve arrhythmia stabilization in 5 patients (83%). Globally, and excluding one patient with spontaneous AT stabilization, ablation success to stabilize the AT was achieved in 16/17 patients (94.1%). Procedural success was achieved in 16/18 patients (88.9%). Rate of one-year freedom from atrial arrhythmias was 66.7%. In the 9 patients with stable ATs ablated during the same period, procedural success (92.4%) and one-year freedom from atrial arrhythmias (65.8%) were similar (Figure, C). 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. Abstract FIGURE