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

Abstract

BackgroundPreclinical 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.MethodsA 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°C) and cellular nonviability (at −20°C), transmural time‐to‐isolation electrical dormancy (TTIED) and cellular nonviability (TTINV) were simulated.ResultsFor cardiac thickness of 0.5, 1.25, 2.0, 3.0, 4.0, and 5.0 mm, the 23°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°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.ConclusionThis 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.

Cryoballoon ablation dosing: From the bench to the bedside and back

“…It identified that for a PV tissue thickness of 3 mm, a TTI of w60 seconds required a total ablation time of w160 seconds for full, circumferential, and transmural penetration of lethal temperature (220 C) into the cardiac tissue. 41 These computational data closely mirror the clinical paradigms that have reported successful outcomes of TTI-guided dosing described in the previous sections. Having said that, this computational model was premised on a circular PV morphology with homogeneous tissue composition and depth.…”

“…Computational modeling may help bridge the gaps between basic science, preclinical research, and clinical observations while generating hypotheses that can be tested in clinical trials. In a recent publication, Getman et al 41 leveraged fundamental understandings of cellular responses to cryothermal energy in order to determine the required duration of cryoablation using Arctic Front Advance and Arctic Front Advance Pro catheters. The model calculated the predicted TTI and the total freeze duration required to achieve circumferential, transmural PVI at varying PV tissue depths.…”

A second cryoballoon system—New and improved?

“…Importantly, significant differences in the biophysical parameters (i.e., rate of cooling, cryoballoon nadir temperatures, thaw times) during cryoablation with the two technologies were reported. Biophysical characteristics during ablation with the Arctic Front Advance cryoballoon have been carefully evaluated via preclinical studies, computational modeling, and randomized controlled trials over the last 15 years and have been used to define dosing algorithms and best practices 2–5 . Despite the similarities between the two cryoballoons, results from this study suggest the PolaRx balloon has unique biophysical parameters and may need ongoing investigation to optimize dosing.…”

A Second Cryoballoon System- new and improved?

“…Biophysical characteristics during ablation with the Arctic Front Advance cryoballoon have been carefully evaluated via pre-clinical studies, computational modeling, and randomized controlled trials over the last 15 years and have been used to define dosing algorithms and best practices. [2][3][4][5] Despite the similarities between the two cryoballoons, results from this study suggest the PolaRx balloon has unique biophysical parameters and may need ongoing investigation to optimize dosing.…”