Real-time guidewire localization using impedance-based electroanatomic mapping: experimental results and clinical validation during cryoballoon ablation of atrial fibrillation

Cryoballoon ablation is an emerging therapy for atrial fibrillation (AF). However, the Arctic Front cryoballoon (Medtronic) cannot be localized on current electroanatomic mapping (EAM) systems. We describe a technique to visualize guidewires in an impedance-based EAM system.

A novel technique for real-time guidewire localization in an EAM (Ensite Velocity, St Jude Medical) was prospectively evaluated among patients referred for cryoballoon AF ablation. The guidewire was visualized as an ‘orb’ on the EAM and localization in each of the pulmonary veins (PVs) compared with orthogonal fluoroscopy, contrast venography, and intra-cardiac echocardiography. Application of the technique in 21 consecutive patients [median age 58 (interquartile range 21); 71.4% male; 85.7% paroxysmal AF] demonstrated agreement with respect to guidewire localization in 82 of 82 (100%) PVs. Discrimination of guidewire position in the left atrial appendage from the left PVs was also demonstrated. When compared with 21 consecutive cryoballoon procedures over the same time period in which the technique was not used, fluoroscopy time was reduced [median 53.2 (25.9) vs. 72.3 (47.6) min, P = 0.008], and a trend towards reduced radiation exposure [median 372 (656.0) vs. 581 (849.9) mGy, P = 0.08] was noted, without effect on acute procedural or mid-term endpoints. Ex vivo assessment of the technique in a saline bath left atrial model demonstrated that the ‘orb’ localizes to the centroid of the exposed portion of the guidewire.

This simple, novel technique provides real-time, accurate guidewire localization to enable guidewire and catheter navigation during cryoballoon AF ablation.