Ablation Procedure
Ablation was performed under general anesthesia in all patients. A detailed electro-anatomical map (EAM) using either CARTO or ESI mapping systems was performed in all patients after vascular and left atrial access, prior to and following ablation. Patients presenting in AF underwent cardioversion to sinus rhythm prior to EAM. In all cases, PVI was the primary ablative strategy and any additional non-PV targets (linear lesions; low-voltage areas) were ablated at the operator’s discretion.
Ablation was performed using either an irrigated, contact force-sensing RF ablation system (Biosense Webster, etc., or Abbott/ESI) or a cryoballoon ablation catheter (Arctic Front Advance and Arctic Front, Medtronic Inc.). For patients undergoing RF ablation, target power delivery to the anterior and posterior LA walls was 35–45 and 25–35 W, respectively. Patients undergoing cryo-balloon ablation underwent fluoroscopic positioning of a 28- or 23mm cryo-balloon to achieve complete PV occlusion as assessed by contrast injection. A minimum of two freeze-thaw cycles (3 min duration) were applied to each vein, sufficient to achieve PV isolation as assessed by a multipolar mapping catheter.
An esophageal temperature probe was placed in all patients during ablation, with temporary cessation of lesion application if significant temperature deviation occurred. During cryoballoon ablation of right-sided pulmonary veins, phrenic nerve pacing was performed, and ablation was terminated if diaphragmatic contractions diminished.
In all cases, PV isolation was determined by demonstrating an entrance block to each vein during sinus rhythm on post-ablation EAM after a 20-minute waiting period. Exit block was demonstrated at the operator’s discretion, as was occult PV reconnection during adenosine infusion.