Relationship between time-to-isolation and freeze duration: Computational modeling of dosing for Arctic Front Advance and Arctic Front Advance Pro cryoballoons

Background Preclinical and clinical studies have utilized periprocedural parameters to optimize cryoballoon ablation dosing, including acute time-to-isolation (TTI) of the pulmonary vein, balloon rate of freezing, balloon nadir temperature, and balloon-thawing time. This study sought to predict the Arctic Front Advance (AFA) vs Arctic Front Advance Pro (AFA Pro) ablation durations required for transmural pulmonary vein isolation at varied tissue depths. Methods A cardiac-specific, three-dimensional computational model that incorporates structural characteristics, temperature-dependent cellular responses, and thermal-conductive properties was designed to predict the propagation of cold isotherms through tissue. The model assumed complete cryoballoon-to-pulmonary vein (PV) circumferential contact. Using known temperature thresholds of cardiac cellular electrical dormancy (at 23 degrees C) and cellular nonviability (at -20 degrees C), transmural time-to-isolation electrical dormancy (TTIED) and cellular nonviability (TTINV) were simulated. Results For cardiac thickness of 0.5, 1.25, 2.0, 3.0, 4.0, and 5.0 mm, the 23 degrees C isotherm passed transmurally in 33, 38, 46, 62, 80, and 95 seconds during cryoablation utilizing AFA and 33, 38, 46, 63, 80, and 95 seconds with AFA Pro. Using the same cardiac thicknesses, the -20 degrees C isotherm passed transmurally in 40, 55, 78, 161, 354, and 696 seconds during cryoablation with AFA and 40, 54, 78, 160, 352, and 722 seconds with AFA Pro. Conclusion This model predicted a minimum duration of cryoballoon ablation (TTINV) to obtain a transmural lesion when acute TTI of the PV was observed (TTIED). Consequently, the model is a useful tool for characterizing CBA dosing, which may guide future cryoablation dosing strategies.