Flexcath advance

One long sheath (FlexCath Advance; Medtronic and SL0; Abbott Medical) was introduced into the LA and RA after the transseptal puncture. A 10-polar circular mapping catheter (Inquiry; AF Division, Abbott Medical, Minneapolis, MN, USA) was positioned at the SVC. All patients underwent PV isolation using a second-generation 28-mm CB catheter inserted through the FlexCath Advance (Medtronic). Balloon positioning and the degree of PV occlusion were evaluated by the injection of a contrast medium diluted at a 1:1 ratio with 0.9% saline. All cryo applications were performed for 180 or 240 s per application alongside one or more additional cryo applications, as determined by the Achieve catheter (Medtronic). During cryo applications to the right PV, continuous phrenic nerve stimulation (10 V for 2.9 ms) was performed using the circular mapping catheter. The delivery of cryo energy was immediately terminated during the loss of phrenic capture [9] (link). Subsequently, PVs were carefully mapped with an Achieve catheter (Medtronic). In the event PV isolation was not achieved, touch-up ablation was performed using an RF catheter (Thermocool, Biosense Webster; Flexability, Abbott Medical; CoolPath, Abbott Medical; or Ablaze, Japan Lifeline, Tokyo, Japan).

All the included studies performed PV isolation using 28-mm CB-A inserted through a 15-Fr steerable sheath (FlexCath Advance; Medtronic Inc, Minneapolis, MN) over a 20-mm diameter inner lumen mapping catheter (Achieve; Medtronic Inc). Optimal PV occlusion was achieved by “proximal-seal” technique. The CB-A was inflated and advanced toward the ostium of each PV. When the balloon nadir temperature exceeded −60 °C, the ablation was terminated. During CB ablation of the right-sided PVs, high output right phrenic stimulation (1500 ms, 20 mA) was performed using a quadripolar catheter within the superior vena cava. If loss of phrenic capture occurred, the cryoapplication was immediately terminated. For LCPVs the following ablation strategies were applied: if an antral occlusion of the LCPV, determined by contrast injection and fluoroscopy, was achieved, the freeze cycle was initiated. If an antral LCPV occlusion could not be obtained, the operators adapted a sequential ablation approach. At first the first superior branch of the LCPV was targeted, followed by ablation of the first inferior branch. In all the studies an antral freezing cycle was applied as much as possible to LCPV.

Cryoballoon ablation was performed under conscious or deep sedation. Femoral venous access was not guided by ultrasound. Access to the left atrium was achieved with a single transseptal puncture with an SL-0 sheath (St. Jude Medical, Minneapolis, Minnesota) using intracardiac echocardiography. The SL-0 sheath was then replaced by a steerable sheath (FlexCath Advance, Medtronic), after which left atrial and pulmonary vein (PV) anatomy were visualised by angiography. In order to record PV signals prior to ablation, an innerlumen mapping catheter (Achieve catheter, Medtronic) was placed through the steerable sheath proximal to each PV ostium. The ablation was performed using the second-generation 28 mm cryoballoon (Arctic Front Advance Cardiac CryoAblation Catheter System; Medtronic, Minneapolis, Minnesota). Until 2017, at least two cryothermal applications (lasting 240 s) were delivered to isolate each vein. In 2017, the approach proposed by Aryana et al was adopted.10 (link) The endpoint of the procedure was electrical isolation of PV signals. This was evaluated using the circular Achieve mapping catheter to verify entrance block of all isolated veins. Pacing within the PV’s was performed to assess exit block if there was doubt of entrance block. Diaphragmatic stimulation was performed during ablation of the right side veins to avoid phrenic nerve injury.