title: Determination of cryothermal injury thresholds in tissues impacted by cardiac cryoablation.
abstract: Despite widespread clinical use of cryoablation, there remain questions regarding dosing and treatment times which may affect efficacy and collateral injury. Dosing and treatment times are directly related to the degree of cooling necessary for effective lesion formation. Human and swine atrial, ventricular, and lung tissues were ablated using two cryoablation systems with concurrent infrared thermography. Post freeze-thaw samples were cultured and stained to differentiate viable and non-viable tissue. Matlab code correlated viability staining to applied freeze-thaw thermal cycles, to determine injury thresholds. Tissue regions were classified as live, injured, or dead based upon staining intensity at the lesion margin. Injury begins at rates of ∼10 °C/min to 0 °C, with non-viable tissue requiring cooling rates close to 100 °C/min to ∼ -22 °C for swine and significantly greater cooling to -26 °C for human tissue (p = 0.041). At similar rates, lung tissue injury began at 0 °C, with human tissue requiring significantly less cooling, to ∼ -15 °C for complete necrosis and -26 °C for swine (p = 0.024). Data suggest that there are no significant differences between swine and human myocardial response, but there may be differences between swine and human lung cryothermal tolerance.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Department of Surgery, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Goff
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Department of Surgery, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Quallich
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Department of Surgery, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Buechler
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Department of Mechanical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Institute for Engineering in Medicine, University of Minnesota, 420 Delaware St. SE, MMC 609, Minneapolis, MN, 55455, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Bischof
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Department of Surgery, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN, 55455, USA; Institute for Engineering in Medicine, University of Minnesota, 420 Delaware St. SE, MMC 609, Minneapolis, MN, 55455, USA. Electronic address: iaizz001@umn.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Iaizzo
mesh_terms: D000818:Animals; D003452:Cryosurgery / Q000009:adverse effects*; D005615:Freezing; D006321:Heart; D006801:Humans; D008168:Lung / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis / Q000209:etiology; D013552:Swine
keywords: Atrial fibrillation; Cryoablation; Cryothermal tolerance; Phrenic nerve palsy