Electroanatomic Mapping and Ablation
All procedures were performed under general anesthesia. Antiarrhythmic agents, if present, were not discontinued. Patients maintained anticoagulant treatment (acenocumarol with INR from 2 to 3.5, or direct oral anticoagulants, with last dose the night before the procedure).
After vascular access was obtained, a double transseptal puncture was performed and intravenous heparin was administered to maintain an activated clotting time of more than 300 seconds. Thereafter, two long sheaths (1 SL0 sheath and 1 Agilis sheath; St. Jude Medical, Inc., St. Paul, MN) were inserted into the left atrium. The following catheters were used: a decapolar catheter WEBSTER® CS Catheter (Biosense Webster) placed in the coronary sinus as a reference (6Fr), a Pentaray® catheter (Biosense Webster) with F curve 2-6-2 mm spacing between electrodes (7Fr) as a high density mapping catheter (10 pairs of electrodes) and a SmartTouch SF with an F curve as an irrigated-tip contact force ablation catheter (7.5Fr).
Three-dimensional geometry of the left atrium and 4 pulmonary veins (PVs) was reconstructed with the use of Carto3 mapping system (Biosense Webster, Inc.). To ensure that mapping catheter is in contact with the tissue, CARTO system features the TPI or Tissue Proximity Indicator, which performs an impedance matrix. When it contacts with the cardiac wall, the catheter has less ion-charged blood, so impedance rises. To carry out the automatic acquisition of points, a series of filters were included. Those used for the acquisition of these maps are the following: Cicle Lenght Filtering (not in AF), Local Activation Time Stability (not in AF), Position Stability, Density and Respiration Gating.
We recorded multiple bipolar signals (filter setting: 30– 300 Hz) from the Pentaray catheter, first in AF and later in SR after electrical cardioversion. Operators mapped carefully to ensure that the entire left atrium anatomy was represented in both the SR and the AF maps. All points within the pulmonary veins and LA appendage were excluded. After both electroanatomical maps were completed, ablation was performed as usual in our center: ipsilateral PV isolation in pairs, with entrance and exit block as the electrophysiological endpoint. In some cases, ablation could also include lines of ablation, at operator’s discretion.
All procedures were performed by two expert operators.