Impact of higher esophageal temperature thresholds on freeze termination rates: comparison of two cryoballoon systems in AF ablation

A prospective observational single-center study with a retrospective analysis of procedural data was conducted to assess the effects of ET thresholds on freeze termination rates. Data from the POLARx™ system (Group A) and the Arctic Front AdvancePro™ system (Group B) were compared. Procedures were guided by pulmonary vein angiography and intracardiac echocardiography, with cryo-dosing based on time-to-isolation (TTI). A standard freeze duration of 180 seconds was employed, with additional applications as necessary. Continuous monitoring of ET was performed using an S-CATH Esophageal Temperature Probe, and freeze applications were terminated when the ET dropped below 15°C. A hypothetical termination rate was calculated for the proposed cut-off of 20°C.

From October 2018 to October 2024, a total of 1,757 patients (50.7% paroxysmal AF) were enrolled, with a mean age of 66.2 years. The cohort included 1,058 males (60.2%) and 699 females (39.8%). Three hundred thirty-patients (18.8%) were treated in group A, and 1,426 patients (81.2%) were assigned to group B. In group B, persistent AF was documented more frequently (55.0% vs. 22.7%, p<0.001). Significant procedural differences were noted, with Group A having lower median dose area products than Group B (701 cGy×cm² vs. 916 cGy×cm², p<0.001). Acute PVI was achieved in 7,116 veins (99.8%), with a median time to isolation of 37 seconds and a single-shot success rate of 91.0%. TTI was recorded in 73.1% of cases, with Group A showing a higher single-shot success rate (93.9% vs. 91.1%, p<0.001). Minimal esophageal temperatures were similar (34.4°C vs. 35.2°C, p=0.125), but minimal balloon temperatures were lower in Group A (-56.0°C vs. -49.0°C, p<0.001). Freeze termination rates due to low ET (<15°C) were equal in both groups (5.5% vs. 5.6%, p=1.0). Hypothetically increased thresholds (<20°C) for freeze termination showed no significant difference (10.8% vs. 10.2%, p=0.51). Freeze termination due to low ET occurred most frequently in the left inferior pulmonary vein (LIPV) (13.3%) and right inferior pulmonary vein (RIPV) (6.9%). Increased ET (<20°C) would significantly raise freeze terminations in the LIPV (23.6%) and RIPV (11.8%).

Raising the ET threshold from 15°C to 20°C for freeze application termination in CBA significantly increases termination rates, especially in the LIPV and RIPV. No significant differences were found between the two available CBA systems regarding freeze terminations or procedural success. While a higher threshold may enhance safety by reducing the risk of AEF, it may also lead to more frequent freeze interruptions.