Catheter ablation procedure
Electrophysiological studies and catheter ablation were performed by experienced operators under intravenous sedation with propofol or dexmedetomidine. Electroanatomical mapping system (Carto 3, [Biosense Webster, Inc., Diamond Bar CA, USA]; Ensite NavX, [Abbott, Abbott Park IL, USA]; or Rhythmia, [Boston Scientific, Boston MA, USA]) were used. Radiofrequency catheter ablation was performed in all cases from October 2014 to March 2016. From March 2016 to December 2018 cryoballoon ablation was performed for paroxysmal AF and for persistent AF in patients considered frail and at high risk of procedure-related complications. Patients with common PVs or a large PV diameter underwent radiofrequency catheter ablation. Five patients with paroxysmal AF underwent laser balloon ablation from July 2018 to September 2018.
In general, Ringer’s acetate was used as a peri-procedural infusion. Infusion volume before the procedure was 0.45 L, infusion volume during the procedure was 0.1 L/h and infusion volume after the procedure was 1 L. Peri-procedural infusion was reduced or avoided if hydration was contraindicated, such as in hemodialysis patients, or in other situations as per the operator’s judgment.
In radiofrequency catheter ablation, circumferential ablation around both ipsilateral PVs was performed using an open-irrigated linear ablation catheter via a Swartz Braided SL0 Transseptal Guiding Introducer Sheath (Abbott) or AGILIS™ NXT Steerable Introducer (Abbott). PV isolation was considered complete when the 20-pole circular catheter no longer recorded any PV potentials.
In cryoballoon ablation, an Arctic Front Advance cryoballoon catheter with a 28-mm balloon size (Medtronic, Inc., Minneapolis MN, USA) was passed into each PV under guidance by fluoroscopy and/or a electroanatomical mapping system. After confirming PV occlusion by pulmonary venography, cryoablation commenced and was usually continued for 180 seconds. If left atrium-PV conduction persisted after cryoballoon ablation, an additional touch-up ablation was performed using an open-irrigated linear ablation catheter with a 3.5-mm tip.
Additional ablation was also performed for any AF triggers originating from non-PV foci induced by isoproterenol infusion, and for spontaneous atrial flutter or atrial tachycardia induced by atrial burst stimuli. Empirical ablation, such as left atrial linear ablation, complex fractionated atrial electrogram ablation, or low-voltage-area (LVA) ablation was also performed according to the operator’s judgment.
Following PV isolation, voltage mapping was performed using a multi-electrode mapping catheter or bipolar 3.5-mm tip catheter during sinus rhythm or with pacing from the right atrium. The presence of LVAs was defined as areas with voltage < 0.5 mV covering ≥ 5 cm2 across the total surface area of the left atrium.
Thermocool SmartTouch (Biosense Webster), Thermocool SmartTouch SF (Biosense Webster), NAVISTAR Thermocool (Biosense Webster), Thermocool SF (Biosense Webster), CELSIUS (Biosense Webster), TactiCath SE (Abbott), or FlexAbility (Abbott) were used for open-irrigated linear ablation catheters. RF energy was applied for 30 s at each site using a maximum temperature of 42°C and maximum power of 35 W. An irrigation flow rate of 17 mL/min was used with Thermocool SmartTouch, NAVISTAR Thermocool, or TactiCath SE catheters; 8 mL/min was used with the other catheters.