Ensite precision

Endocardial geometry creation relied on impedance (EnSite Precision; Abbott Inc) and magnetic (MediGuide™ or EnSite Precision; Abbott Inc) points acquisition in sinus rhythm. In addition to geometry, voltage data were acquired, and electroanatomical mapping (EAM) was created by the EnSite Precision cardiac mapping system (EAM-endoLV). To improve accuracy, field scaling and respiratory compensation were applied. Bipolar electrograms were filtered at 30–300 Hz. Electrical identification of scar areas was done through bipolar EAM using a voltage amplitude–based criterion (with values <0.3 mV identifying “deep scar” and values >1.5 mV healthy myocardium). Fractionated signals identified either by the physician per-procedure using Jaïs and colleagues’ definition of local abnormal ventricular activation¹⁶ (link) or through EnSite Precision fractionation maps (threshold = 3) were used to locate scar areas and arrhythmogenic substrate. Voltage data from EAM was our gold standard in the clinical decision to determine the ablation locations.

Percutaneous femoral venous access was obtained using vascular ultrasound guidance. Two 8-Fr sheaths were placed in the right femoral vein; one 10-Fr long sheath and another 7-Fr sheath were placed in the left femoral vein. A 9-Fr ICE catheter (ViewFlex, Abbott, St. Paul, MN, USA) was inserted through the 10-Fr long sheath in the left femoral vein and advanced to the inferior vena cava (IVC) while maintaining an echo-free space at the tip of the transducer. The ICE catheter was then advanced toward the RA. A 6-Fr decapolar catheter (Inquiry Diagnostic Catheter, Abbott) was next inserted into the left femoral vein and into the IVC under EAM guidance (EnSite Precision, Abbott) to generate IVC, SVC, RA, and CS geometries. The 0.035-inch RF wire (VersaCross RF Wire, Baylis Medical, Montreal, QC, CA) was visualized on the EnSite system using “mapping mode” on the dedicated DuoMode extension cable (Baylis Medical) (Fig. 1).Fig. 1

Set up for visualization of 0.035 RF wire (VersaCross RF Wire, Baylis Medical Company, Montreal QC, CA). A DuoMode extension cable (Baylis Medical) was used to connect the RF wire to the EnSite velocity cardiac mapping system pin box (Abbott, St. Paul, MN) to enable visualization during superior vena cava (SVC) cannulation, drop-down to the fossa ovalis, and transseptal puncture

Procedures were performed under general anesthesia in patients younger than 14 years, while local anesthesia and conscious sedation were used in older patients. Femoral vein access was obtained under ultrasound guidance. The 3D EAM system (EnSite NavX, Ensite Velocity, Ensite Precision, Abbott, St. Paul, MN, USA or Carto 3, Biosense Webster, Diamond Bar, CA, USA) was used for guidance of the catheters in the heart and advancement through the vasculature.
After femoral vein access was obtained, a 10-polar diagnostic catheter was advanced into the right atrium. The catheter was used to construct a partial 3D rendering of the right atrium and to mark the location of His potential. The catheter was then placed in the coronary sinus. Next, an additional 4- or 10-polar diagnostic catheter was inserted into the heart and placed on the basal section of the right side of the interventricular septum.
A standard electrophysiology study followed, with the aim of tachycardia induction. In cases of clear ventricular preexcitation, the induction of tachycardia was left to the physician’s discretion. If induction of tachycardia was not achieved or conduction over the accessory pathway (AP) was not detected, the protocol was repeated with an isoprenaline challenge. Standard diagnostic maneuvers were employed as needed to determine the type of induced tachycardia.