All patients gave informed consent prior to the ablation procedure. The choice to RMN or MCN-CF RFCA was decided according to patient preference. In all subjects, left atrial (LA) thrombi were excluded by transesophageal echocardiography, and LA anatomy was acquired by contrast-enhanced high-resolution thoracic computer tomography prior to the procedure. All ablation procedures were performed with conscious sedation using intravenous sufentanil, midazolam and/or propofol under continuous monitoring of blood pressure and oxygen saturation. For the electrophysiological procedure, all catheters were advanced via the femoral veins. A 6F steerable decapolar catheter (Bard Dynamic Tip®, Bard Inc., Lowell, MA, USA) was positioned in the coronary sinus. After a fluoroscopically guided double transseptal puncture an SL1® sheath (St. Jude Medical, Inc., St. Paul, MN, USA) in the RMN group or an Agilis® deflectable sheath (St Jude Medical Inc., St. Paul, MN, USA) in the MCN-CF group were advanced into the LA. In the RMN group, a 3.5 mm open-irrigated, magnetic mapping and ablation catheter (Navistar® Thermocool® RMT, Biosense-Webster, Diamond Bar, USA) was advanced through the sheath into the LA, whereas in the MCN-CF group, a manually guided, open irrigated tip and contact-force sensing mapping and ablation catheter (Thermocool® SmartTouch® Surround Flow®, Biosense-Webster, Diamond Bar, USA) was used. After January 2010, a circular mapping catheter was initiated as a standard tool during every pulmonary vein ablation. The circular mapping catheter (Lasso®, Biosense Webster, Diamond Bar, CA, USA) was positioned within the PV ostium to monitor electrical activity during ablation and to verify electrical pulmonary vein isolation. Intravenous heparin was administered immediately after the transseptal puncture to maintain an activated clotting time (ACT) of 300–350 s throughout the procedure. Patients presenting with persistent atrial fibrillation underwent electrical cardioversion prior to mapping and ablation. Circumferential pulmonary vein ablation was performed using a three-dimensional mapping system (Carto® XP or Carto® 3, Biosense Webster, Diamond Bar, CA, USA) in conjunction with the integrated CT image of the LA and real-time fluoroscopy. To assure an accurate 3D model acquisition, respiratory gating was performed. In the RMN group, the Niobe II® magnetic navigation system (Stereotaxis) and a joystick-controlled motor drive (Cardiodrive®, Stereotaxis) were utilized for remote magnetic navigation of the ablation catheter, whereas in the MCN-CF group, the ablation catheter was guided manually. In the case of persistent AF, additional ablation lines were considered during the repeat ablation in case of persistent isolation of the pulmonary veins. The RMN system has been described in detail before [
3]. Briefly, two permanent magnets located on either side of the procedure desk generate a magnetic field (0.08 Tesla) within the patient. The magnetic ablation catheter incorporates four magnets in the distal portion of the catheter. A change of the desired vector for catheter orientation on a computer screen results in alteration of the magnetic field generated by the permanent magnets and thereby corresponding deflection of the magnetic catheter within the heart. The joystick-controlled motor drive allows catheter advancement and retraction. Thus, the system provides complete remote catheter navigation for mapping and ablation. RF current was delivered for 30–60 s per lesion, applying 40 W (irrigation flow rate 30 ml/min) or 30 W at the posterior LA wall (irrigation flow rate 17 ml/min) with the generator (Stockert®, Biosense Webster) in a power-controlled mode and with an upper temperature limit of 45 °C in RMN group. An interlesion distance of ≤ 6 mm was aimed for. In the MCN-CF group, contact force was continuously monitored. According to manufacturer’s protocol, a contact force of 5–20 g was targeted during ablation. A force time integral (FTI) with an aim of 330 g seconds was used to determine acceptable lesions. Excessive tissue contact force (> 50 g) was visually indicated for safety considerations. Endpoint of the ablation procedure was the electrical isolation of all PVs defined as bidirectional conduction block. This was verified by the lasso catheter and a careful and repeated mapping for residual potentials around the entire circumference of the PV ostia, and pacing from multiple sites within the circumferential line. All pulmonary veins were examined at the end of the procedure resulting in waiting periods of > 30 min for the left superior pulmonary vein (LSPV) and left inferior pulmonary vein (LIPV) and ca. 5 min for right superior pulmonary vein (RSPV) and right inferior pulmonary vein (RIPV). No drugs were used to illicit triggers or uncover dormant isolation. All procedures were performed by the same experienced operators.