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).