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

Abstract

Background: Unstable reentrant atrial tachycardias (ATs) (i.e., those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate. We tested a strategy to achieve arrhythmia stabilization into mappable stable ATs based on the detection and ablation of rotors.

Methods: All consecutive patients from May 2017 to December 2019 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, without dedicated software. In patients without detectable rotors, sites with spatiotemporal dispersion (i.e., all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted. Ablation success was defined as conversion to a stable AT or sinus rhythm.

Results: Ninety-seven patients with reentrant ATs were ablated. Of these, 18 (18.6%) presented unstable circuits. Thirteen (72%) patients had detectable rotors (median 2 [1-3] rotors per patient); focal ablation was successful in 12 (92%). In the other 5 patients, 17 sites with spatiotemporal dispersion were identified and targeted. Globally, and excluding 1 patient with spontaneous AT stabilization, ablation success 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).

Conclusions: 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.

Keywords: ablation; atrial tachycardia; atypical atrial flutter; high-density mapping; rotor.

Figure 1

Schematic rationale of rotor detection using a hypothetical 12-pole mapping catheter; A. A stable rotor would theoretically show fractionated quasi-continuous electrograms on the bipoles placed on the rotor core (6–7), because the mapping area of that bipole would detect electrical activity during almost all the cycle length. Other bipoles may (or may not) show some degree of fractionation. Red arrow represents rotor spiral wavefront; B. If the rotor core meanders around the neighboring tissue, the fractionation would move between different bipoles through time, resulting in non-continuous fractionation. Red arrow represents meandering of the rotor core.

Figure 2

Detailed mapping and ablation approach; *Unstable atrial tachycardia (AT) is defined as having continuous circuit modification; †Spatiotemporal dispersion mapping was biatrial in all patients apart from one, in whom, after failed rotor ablation in the left atrium (LA), sites with spatiotemporal dispersion were successfully targeted in the LA before considering right atrium rotor mapping; AF — atrial fibrillation.

Figure 3

Representative examples of rotors and sites with spatiotemporal dispersion; A. Examples of rotors (dotted lines); upper panel and middle panel: IntellaMap ORION catheter; rotors detected in a single bipole; lower panel: Advisor HD Grid catheter; rotor detected in 2 adjacent bipoles (D1–D2 and D2–D3); note the low voltage of electrical signals in the middle and lower panel; B. Examples of sites with spatiotemporal dispersion and non-continuous fractionation (dotted lines); arrows represent hypothetical trajectory of a meandering rotor core; upper panel: IntellaMap ORION catheter; middle panel: PentaRay NAV catheter (PR); lower panel: Advisor HD Grid catheter; paper speed: 200 mm/s; ORB — Woven Orbiter catheter; blue bipoles around tricuspid annulus and green bipoles into the coronary sinus.

Figure 4

Location of rotors (pink dots) and sites with spatiotemporal dispersion and non-continuous fragmented electrograms (green dots). Eleven (42%) rotors were related to the antra of the pulmonary veins, especially the anterior aspect of the right superior pulmonary vein (RSPV; n = 6) and the ridge between the left atrial appendage and the left superior pulmonary vein (LSPV; n = 4); CS — coronary sinus; FO — foramen ovale; IVC — inferior vena cava; LIPV — left inferior pulmonary vein; LA — left atrium; RA — right atrium; RIPV — right inferior pulmonary vein; SVC — superior vena cava.

Figure 5

Estimated survival free from atrial arrhythmias, excluding a 3-month blanking period, in included patients and patients with ablation of mappable reentrant atrial tachycardias (ATs) during the same period.