Effect of pulmonary vein cryoballoon ablation in dogs with coolant-nitrogen

Abstract

Background: The Arctic Front Advance System with nitrous oxide (N 2 O) refrigerant is the leading system for the cryoballoon ablation of atrial fibrillation (AF). A novel cryoablation system with nitrogen (N 2 ) refrigerant was developed with technical improvements seeking to improve outcomes. Cryoballoon ablation with the N 2 refrigerant may be effective and safe for pulmonary vein isolation (PVI).Methods: In total, 16 dogs were included in the study, of which 13 underwent PVI procedures, and 3 served as baseline controls. Cryoballoons (Cryofocus, Int.) with N 2 refrigerant were used for the study group, which comprised 8 dogs, and second-generation cryoballoons with N 2 O refrigerant (Arctic Front Advance; Medtronic, Inc., MN, USA) were used for the control group, which comprised 5 dogs. Three dogs of the study group and 2 dogs of the control group were euthanized on the same day post-ablation. The other 8 dogs of the two groups were euthanized 1 month post-ablation. The removed organs were examined for gross anatomy and histological review. Results:The average ablation times for each pulmonary vein (PV) in the study group were less than those in the control group (1.1±0.3 vs. 2.0±0.8; P=0.006). The procedure duration of the study group was shorter than that of the control group (379±46 vs. 592±162 s; P=0.013). And the time to isolation (TTI) was similar between the groups. The PVI rate of the single-ablation was higher in the study group than the control group (92.9% vs. 60.0%; P=0.05). In relation to safety, there was no evidence of thrombus, esophageal injury, or pericardial tamponade in any of the dogs. Only 1 incidence of self-limited phrenic nerve paralysis (PNP) was observed in the control group.Conclusions: The novel cryoablation system with the N 2 refrigerant had better efficacy than and similar safety to that of the system (Medtronic, Int.) with the N 2 O refrigerant.

Liquid Nitrogen Cryoballoon Ablation System for Paroxysmal Atrial Fibrillation

“…The other concern is that the liquid nitrogen CBA catheter has a more rapid freezing effect, where temperature drops 3.07 °C per second, compared with 1.59 °C per second with nitrous oxide CBA catheters). 7 Although more rapid freezing effect might be more effective in achieving PVI, the temperature could possibly be more unstable and uncontrollable, which might increase the potential safety risks. The different physical properties suggest that using the liquid nitrogen as a cryogen requires a more considered and sophisticated design and manufacture of the CBA system, and more intense safety monitoring during and after the CBA procedure.…”

“… 18 , 25 Further research is warranted to testify the efficacy of this liquid nitrogen CBA system for various types of AF. Furthermore, because previous published literature 20 , 26 and results from animal experiment of the liquid nitrogen CBA system 7 showed the incidence of severe esophageal injury is relatively low, esophageal injury was monitored and evaluated only by observing the gastrointestinal symptoms and signs during and after the procedure. However, we acknowledge that that might not be sufficient to comprehensively evaluate esophageal injury, and therefore the incidence of esophageal injury might be underestimated.…”

“…An animal study has preliminarily validated its operability, safety, and efficacy for PVI. 7

Figure 1 Liquid Nitrogen Cryoballoon Ablation System (A) Ablation catheter with cryoballoon located distally with circular mapping catheter at tip, (B) steerable sheath with handle, (C) cryogen storage and delivery system with controlling interface.

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Cryoablation

“…Recently, a liquid nitrogen-based CBA system (Cryofocus Medtech) has been developed for treating atrial fibrillation. 6 Unlike CBA systems using nitrous oxide, which primarily rely on the Joule-Thomson effect for freezing, liquid nitrogen CBA primarily achieves tissue freezing through vaporization. To facilitate this process, liquid nitrogen CBA is equipped with as many as 18 refrigerant release channels to ensure a uniform release of liquid nitrogen.…”

“…An animal experiment was conducted preliminarily using liquid nitrogen CBA to assess its feasibility, safety, and effectiveness for the PVI. 6 In total, 13 dogs underwent PVI: 8 dogs received treatment with liquid nitrogen CBA and 5 dogs received treatment with AFA. The PVI success rate following a single ablation was higher in the liquid nitrogen CBA group compared with the AFA group (92.9% vs 60.0%; P = 0.05), although the time to isolation was similar between the groups (48.1 ± 29.1 seconds vs 52.3 ± 51.2 seconds).…”