Introduction:

Arrhythmia recurrence after RF catheter ablation is often due to catheter instability, ineffective power delivery and lesion arrhythmogenicity. A new technology delivers focal, linear and transmural lesions with ultra-low temperature cryoablation (ULTC) temperatures below -170°C. The aim of this study was to assess the safety, efficacy, and long-term durability of ULTC lesions in acute and chronic swine animal models.

 Methods:

The ULTC system uses near-critical nitrogen and ablation catheters with a continuous cooling along 11cm. The same catheter was adjusted to specific anatomies using pre-shaped stylets or focal tip exposure only. ULTC was applied from 20 sec to 2 min in 10 swine, to isolate PVs, SCV, LAA, RAA and as well as linear and focal lesions in the atrial tissue. Acute and 90-day chronic success was evaluated by pacing manoeuvres, voltage mapping and histology for all lesions. Histopathology was also performed in surrounding non-targeted tissues.

 Results:

No procedural complications occurred. Cryoadherence was observed at all ULTC’s assuring catheter stability at target locations. In 100% of ULTCs, local PV electrograms were eliminated after the first cryo application from 30 to 60 sec. Voltage reductions from 4.24 to 0.35mV were acutely observed following a single 45sec ULC around the LAA, completing its isolation. Conduction block with reductions from 2.6 to 0.20mV; 1.97 to 0.43mV and 1.21 to 0.43mV were observed, following a single 30sec ULTC at the RSPV, LA septum and SVC respectively. Pre and post ULTC electrograms, fluoroscopic, histologic and 3D imaging are depicted in Figure 1. In all animals, voltage maps and histopathology showed durable and transmural lesions with no gaps. Histology showed well delineated continuous lesions, with intact collagen. No chronic injuries were found in surrounding tissues.

Conclusions:

Ultra-low temperature cryoablation results show successful acute and chronic PVI, as well as the durability of other non-PV lesions at 90 days. The novel technology offers a good safety profile with a more stable catheter and shorter ablation times, when compared to classic RF ablation.