Catheter ablation (CA)
Pre-procedure preparation and techniques for PsAF ablation have been
described previously.14,15 In brief, all patients
received oral anticoagulation at least 4 weeks prior to the ablation
procedure. Anti-arrhythmic drugs were discontinued for at least five
half-lives prior to ablation. After exclusion of left atrial (LA)
thrombus using trans-esophageal echocardiography, CA was performed under
mild deep sedation. Continuous and bolus heparin administered with a
target activated clotting time of 300-400 seconds.
The initial ablation step involved segmental antral PVI (in AF or SR)
with the guidance of a large circular mapping catheter (Lasso 20-30 mm;
Biosense-Webster Inc, Diamond Bar, CA, USA). Ablation was performed
using a non-contact force sensing open-irrigated 3.5 mm-tip ablation
catheter (Cool PathTM Duo,
FlexAbilityTM; St jude Medical or ThermoCool/SF;
Biosense Webster) with a power limit of 25-35W. The procedural endpoint
of PVI was bidirectional electrical conduction block between the LA and
PVs.14 Following PVI, linear ablation or EGM-guided
ablation was performed.
In LINE-group, following roof line ablation (connecting the superior
PVs), MI line ablation was performed with the endpoint of a
bidirectional electrical conduction block across the
lines.16,17 MI line ablation was performed from the
mitral annulus to the lower pole of the left inferior PV along the
shortest line located (3-4 o’clock in the left-anterior oblique view).
Epicardial ablation within the coronary sinus (CS) was subsequently
added in cases with incomplete block from endocardial ablation. Ablation
setting during linear ablation was as follows: a power output of 30-40 W
on the roof and endocardial MI and 20-25W on the epicardium within the
CS.
In the EGM-group, ablation was performed at all sites displaying any of
the following EGM features: 1) continuous electrical activity, 2) rapid
activity with cycle length (CL) shorter than the mean LA appendage AF
CL, 3) complex and fractionated electrograms, and 4) a gradient of
activation (a temporal gradient of at least 70 ms between the distal and
proximal bipoles on the map electrode, potentially representing a local
circuit) with the endpoint of AF termination.8 The
power output during EGM-guided ablation was 30W except for the posterior
wall adjacent to the esophagus (20W with ablation termination upon
abolition of the local specific electrograms). Electrical cardioversion
was performed at the end of the procedure where elimination of targeting
signals in both right and left atrium failed to terminate AF.
EGM-guided ablation was performed by only one experienced operator. Two
experienced operators performed linear ablation with consistent ablation
endpoints between operators. In all cases, the presence/absence of
dormant conduction was tested by administration of isoproterenol (4 ug)
and adenosine triphosphate (10-20 mg) in each PV after a minimum waiting
period of 30 minutes after PVI. Dormant conduction was eliminated by
additional radiofrequency (RF) applications. In cases with evidence of
non-PV foci, the ablation strategy involved targeting non-PV foci.
Superior vena cava (SVC) isolation was performed if arrhythmogenicity
was detected in the SVC. Sustained AT occurring during the procedure was
also mapped and ablated. Carvotricuspid isthmus linear ablation was
routinely performed in all patients regardless of the presence or
absence of documented typical atrial flutter. 3D-electroanatomical
mapping (EAM) systems (CARTO3, Biosense-Webster Inc. or Navx, St Jude
Medical, Inc, Minneapolis, MN, USA) were used during CA.
In the case of re-do procedures, the ablation strategy involved
re-isolation of pulmonary veins (where indicated), and/or additional
EGM-guide ablation, and/or linear ablation (roof and MI lines where
necessary) with operator’s discretion. Non-PV foci were targeted during
the re-do procedure in the same way as the index procedure (following
administration of isoproterenol [4 ug] and adenosine triphosphate
[10-20 mg]). In case with AT recurrence, the arrhythmia was targeted
with AT non-inducibility as the endpoint (no AT inducible with burst
pacing up to 200ms).