title: Simulation and evaluation of freeze-thaw cryoablation scenarios for the treatment of cardiac arrhythmias.
abstract: BACKGROUND
  Cardiac cryoablation is a minimally invasive procedure to treat cardiac arrhythmias by cooling cardiac tissues responsible for the cardiac arrhythmia to freezing temperatures. Although cardiac cryoablation offers a gentler treatment than radiofrequency ablation, longer interventions and higher recurrence rates reduce the clinical acceptance of this technique. Computer models of ablation scenarios allow for a closer examination of temperature distributions in the myocardium and evaluation of specific effects of applied freeze-thaw protocols in a controlled environment.
  
  
  METHODS
  In this work multiple intervention scenarios with two freeze-thaw cycles were simulated with varying durations and starting times of the interim thawing phase using a finite element model verified by in-vivo measurements and data from literature. To evaluate the effects of different protocols, transmural temperature distributions and iceball dimensions were compared over time. Cryoadhesion durations of the applicator were estimated in the interim thawing phase with varying thawing phase starting times. In addition, the increase of cooling rates was compared between the freezing phases, and the thawing rates of interim thawing phases were analyzed over transmural depth.
  
  
  RESULTS
  It could be shown that the increase of cooling rate, the regions undergoing additional phase changes and depths of selected temperatures depend on the chosen ablation protocol. Only small differences of the estimated cryoadhesion duration were found for ablation scenarios with interim thawing phase start after 90 s freezing.
  
  
  CONCLUSIONS
  By the presented model a quantification of effects responsible for cell death is possible, allowing for the analysis and optimization of cryoablation scenarios which contribute to a higher clinical acceptance of cardiac cryoablation.
authors.affiliation: Institute of Electrical and Biomedical Engineering, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnöfer-Zentrum 1, Hall in Tirol, 6060, Austria. michael.handler@umit.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Handler
authors.affiliation: AFreeze GmbH, Eduard Bodem Gasse 8, Innsbruck, 6020, Austria. gerald.fischer@afreeze.com.
authors.forename: Gerald
authors.initials: G
authors.lastname: Fischer
authors.affiliation: Institute of Electrical and Biomedical Engineering, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnöfer-Zentrum 1, Hall in Tirol, 6060, Austria. m.seger@fh-kaernten.at.|Medical Engineering and Healthcare IT, Carinthia University of Applied Sciences, Primoschgasse 10, Klagenfurt, 9020, Austria. m.seger@fh-kaernten.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Seger
authors.affiliation: Institute of Electrical and Biomedical Engineering, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnöfer-Zentrum 1, Hall in Tirol, 6060, Austria. roland.kienast@umit.at.
authors.forename: Roland
authors.initials: R
authors.lastname: Kienast
authors.affiliation: Institute of Electrical and Biomedical Engineering, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnöfer-Zentrum 1, Hall in Tirol, 6060, Austria. friedrich.hanser@umit.at.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hanser
authors.affiliation: Institute of Electrical and Biomedical Engineering, University for Health Sciences, Medical Informatics and Technology, Eduard Wallnöfer-Zentrum 1, Hall in Tirol, 6060, Austria. christian.baumgartner@umit.at.|Institute of Health Care Engineering with European Notified Body of Medical Devices, Graz University of Technology, Kopernikusgasse 24, Graz, 8010, Austria. christian.baumgartner@umit.at.
authors.forename: Christian
authors.initials: C
authors.lastname: Baumgartner
mesh_terms: D001145:Arrhythmias, Cardiac / Q000601:surgery*; D001831:Body Temperature; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D003080:Cold Temperature; D003198:Computer Simulation; D003452:Cryosurgery / Q000295:instrumentation / Q000379:methods*; D006329:Heart Conduction System / Q000002:abnormalities / Q000601:surgery; D006801:Humans; D019060:Minimally Invasive Surgical Procedures; D008955:Models, Cardiovascular; D009206:Myocardium / Q000473:pathology; D044367:Phase Transition