2.1 | Ablation procedure
Prior to the ablation procedure, cardiac computed tomography and transesophageal echocardiography were performed in all patients to define left atrial anatomy, and to rule out intracardiac thrombus. After obtaining venous access, a steerable, decapolar catheter (Dynamic XT, Boston Scientific, Marlborough, MA) was positioned within the CS. Left atrial access was gained by transseptal puncture or via a patent foramen ovale. Heparin was administered to achieve an activated clotting time of more than 350 seconds. An electroanatomical 3D mapping system (CARTO 3, Biosense Webster, Diamond Bar, CA) was used in all cases and left atrial geometry reconstructed with a multipolar mapping catheter (Pentaray, Biosense Webster, Diamond Bar, CA). Left atrial voltage maps were generated before and after VOM-EI and low-voltage area was defined as bipolar voltage amplitude below 0.5 mV (Figure 1). Radiofrequency ablation of the mitral isthmus was performed endocardially and from within the CS as necessary to achieve bi-directional block.
For ablation, an irrigated‐tip ablation catheter (ThermoCool SmartTouch SF, Biosense Webster, Diamond Bar, CA) was used with a power of 20-25 W in the CS and 35 W in the atrium. Bi-directional block was confirmed by differential pacing on both sides of the mitral isthmus according to standard criteria.1 Radiofrequency ablation of targets other than the mitral isthmus was performed at the discretion of the operator and as mandated by the clinical situation.