Mapping protocol and rotor identification
Mapping was performed using conventional high-density electroanatomical
mapping catheters (IntellaMap ORION, Boston Scientific Inc.; PentaRay
NAV, Biosense Webster Inc.; or Advisor HD Grid, Abbott Medical, Inc.)
and their respective mapping system (Rhythmia, Carto3 or Ensite
Precision). Bipolar voltage maps were created, with the threshold for
dense scar set bellow 0.03 mV in all navigation systems, in order to
allow annotation of low-voltage signals.
For patients with AT as initial rhythm, or AT induced from sinus rhythm,
and posterior destabilization, mapping was initiated within the right
atrium (RA) or LA, depending on the suspected origin of the AT according
to initial entrainment. If destabilization occurred before or during
entrainment, mapping was started within the atrium in which initial
disorganization of electrical signals during AT presumably led to AF.
For patients with AF as initial rhythm, mapping was initiated in the
atrium with faster cycle length according to the Orbiter catheter
signals. If rotors were identified in the initially mapped atrium, rotor
ablation was performed; if rotors were not present, or rotor ablation
was not successful to convert AF into AT or sinus rhythm, the other
atrium was then mapped for rotor identification.
Rotors were subjectively identified as fractionated continuous (or
quasi-continuous) bipolar EGMs on 1-2 adjacent bipoles of the mapping
catheter, using a digital recorder (Bard LabSystem Pro) at 200 mm/s
speed (Figure 1, panel A). Filters for bipolar signals were set at 30
and 250 Hz, with notch filter. When such EGMs were identified, the
mapping catheter was kept still for 10 seconds to confirm temporal
stability of the rotor, which was then annotated with a manual marker
deployed on an electroanatomical bipolar voltage map. After mapping was
complete, the mapping catheter was repositioned in sites with rotors to
confirm temporal permanence before ablation. Temporally unstable rotors
were neither annotated nor targeted for ablation.
If rotors were absent in both atria, or rotor ablation was unsuccessful
to stabilize or terminate AF, sites with STD (i.e. all the AF cycle
length comprised within the different bipoles of the mapping catheters)
plus non-continuous fragmentation on single bipoles, arbitrarily defined
as continuous bipolar EGMs with >4 deflections and total
duration >70 ms, were manually annotated and targeted for
ablation (Figure 1, panel B). At least 10 seconds of temporal stability
was also required for these sites.