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 cardiacarrhythmias by cooling cardiac tissues responsible for the cardiac arrhythmia tofreezing temperatures. Although cardiac cryoablation offers a gentler treatment thanradiofrequency ablation, longer interventions and higher recurrence rates reduce theclinical acceptance of this technique. Computer models of ablation scenarios allow fora closer examination of temperature distributions in the myocardium and evaluation ofspecific effects of applied freeze-thaw protocols in a controlled environment.Methods: In this work multiple intervention scenarios with two freeze-thaw cycleswere simulated with varying durations and starting times of the interim thawing phaseusing a finite element model verified by in-vivo measurements and data from literature.To evaluate the effects of different protocols, transmural temperature distributions andiceball dimensions were compared over time. Cryoadhesion durations of the applicatorwere estimated in the interimthawing 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 undergoingadditional phase changes and depths of selected temperatures depend on the chosenablation protocol. Only small differences of the estimated cryoadhesion duration werefound for ablation scenarios with interim thawing phase start after 90 s freezing.Conclusions: By the presented model a quantification of effects responsible for celldeath is possible, allowing for the analysis and optimization of cryoablation scenarioswhich contribute to a higher clinical acceptance of cardiac cryoablation.