Afocus

The methods of our ablation strategy have been described in detail elsewhere. 5, 7 In brief, all procedures were performed under deep sedation with midazolam, fentanyl, and a continuous propofol infusion. A diagnostic catheter was positioned inside the coronary sinus. After double transseptal punctures were performed by a modified Brockenbrough technique, 2 SL1 transseptal sheaths (St. Jude Medical) were advanced into the LA. Activated clotting time was assessed every 30 minutes, and intravenous heparin boluses were administered, targeting an activated clotting time 4250 seconds. Both transseptal sheaths were continuously flushed with heparinized saline to prevent thrombus formation. One SL1 sheath was then used for the multielectrode spiral mapping catheter (Lasso, Biosense Webster Inc, Diamond Bar, CA, or AFocus, St. Jude Medical). Three-dimensional electroanatomic LA reconstruction with a 3-dimensional mapping system (CARTO, Biosense Webster) was performed with a conventional 3.5-mm irrigated-tip ablation catheter (THERMOCOOL NAVISTAR, Biosense Webster). Selective angiography of each pulmonary vein (PV) via right anterior oblique 301 and left anterior oblique 401 fluoroscopic views was then performed.

Ipsilateral CPVI was performed using entrance and exit block as the electrophysiological end point. Cavotricuspid isthmus (CTI) ablation was then completed in all patients.
After CPVI and CTI ablation, cardioversions were delivered to restore SR. If cardioversion was unsuccessful, ablation was continued using the STEPWISE approach described below. If AF organized into an atrial tachycardia (AT), activation and entrainment mapping were performed to identify the mechanism of AT and the optimal site for ablation.
Once SR was restored, high-density bipolar voltage mapping of the left atrium (LA) was performed with >500 points in each patient (at least 300 surface points were requested) using an A-Focus (St. Jude Medical, St. Paul, MN) catheter with the interspace of 3.0 mm to identify the low-voltage zones (LVZs: 0.1-0.4 mV) and transitional zones ( 0.4-1.3 mV). 16 (link) To avoid poor contact points, we set the interior and exterior projection distance at 5 mm from the geometry surface. We attempted to homogenize all tissue in the LVZs and eliminate the complex electrograms in the transitional zones. Dechanneling was done if necessary per the substrates. The substrate modification strategy used during SR is schematically shown in Figure 1 and demonstrated in Figure 2, which is the same as the strategy used in our pilot study. 18 (link)