Purpose: We sought to quantify the capabilities of a commercially available cooling device to protect the esophagus from RF injury in an animal model and develop a mathematical model to describe the system and provide a framework from which to advance this technology.Methods: A series of ablations (10 W, duration 30-45 seconds) were performed directly on exposed swine esophagus. Control ablations were performed with static 37°C water, and treatment ablations were performed with water (range 5°C-37°C) circulating within the device. Mucosal lesions were evaluated visually and with target tissue histology. A mathematical model was then developed and compared against the experimental data.Results: All 23 ablations (100%) performed under control conditions produced visible external esophageal lesions; 12 of these (52%) were transmural. Under treatment conditions, only 5 of 23 ablations (22%) produced visible external lesions; none (0%) were transmural. Transmurality of lesions decreased as circulating water temperature decreased, with absolute reduction ranging from 5.1% with the use of 37°C water (p=0.7) to 44.5% with the use of 5°C water (p<0.001). Comparison to the mathematical model showed an R^2 of 0.75, representing good agreement.Conclusions: Under worst-case conditions, with RF energy applied directly to the adventitial side of the esophagus, internal esophageal cooling with an esophageal cooling device provides significant protective effect from thermal injury. A mathematical model of the process provides a means to further investigate this approach to preventing esophageal injury during RF ablation and can serve to guide ongoing clinical investigations currently in progress.
Introduction Recent clinical data show that high-power, short-duration (HPSD) radiofrequency (RF) ablation can result in a similar esophageal injury rate as traditional low-power, long-duration (LPLD) ablation. Existing methods to prevent esophageal injury have yielded mixed results and can result in prolonged procedure time, potentially increasing the incidence of post-operative cognitive dysfunction. A new esophageal cooling device currently available for whole-body temperature modulation is being studied for the prevention of esophageal injury during LPLD RF ablation and cryoablation. We sought to develop a mathematical model of HPSD ablation in order to quantify the capability of this new esophageal cooling device to protect from esophageal injury under high-power conditions. Methods Using a model we developed of HPSD RF ablation in the left atrium, we measured the change in esophageal lesion formation and the depth of lesions (measured as percent transmurality) with the esophageal cooling device in place and operating at a temperature from 5°C to 37°C. Tissue parameters, including thermal conductivity, were set to average values obtained from existing literature, and energy settings were evaluated at 50W for between 5 and 10 seconds, and at 90W for a duration of 4 seconds. Results Esophageal injury as measured by percent transmurality was considerably higher at 50W and 10s duration than at 90W of power with 4s duration, although both settings showed potential for esophageal injury. The protective effect of the esophageal cooling device was evident for both cases, with a greater effect when using 50W for 10s (Figure 1). At the coldest device settings, using a 5 min pre-cooling period also reduced the transmurality of the intended atrial lesions. Esophageal protection in HPSD ablation Conclusions Esophageal cooling with a new patient temperature management device shows protective effects against thermal injury during RF ablation across a range of tissue thermal conductivity, using a variety of high-power settings, including 90W applied for 4 seconds. Adjusting the cooling power by adjusting the circulating water temperature in the device allows for a tailoring of the protective effects to operating conditions. Acknowledgement/Funding Attune Medical
Background: Increasing data suggest that elevated body temperature may be helpful in resolving a variety of diseases, including sepsis, acute respiratory distress syndrome (ARDS), and viral illnesses. SARS-CoV-2, which causes coronavirus disease 2019 (COVID-19), may be more temperature sensitive than other coronaviruses, particularly with respect to the binding affinity of its viral entry via the ACE2 receptor. A mechanical provision of elevated temperature focused in a body region of high viral activity in patients undergoing mechanical ventilation may offer a therapeutic option that avoids arrhythmias seen with some pharmaceutical treatments. We investigated the potential to actively provide core warming to the lungs of patients with a commercially available heat transfer device via mathematical modeling, and examine the influence of blood perfusion on temperature using this approach. Methods: Using the software Comsol Multiphysics, we modeled and simulated heat transfer in the body from an intraesophageal warming device, taking into account the airflow from patient ventilation. The simulation was focused on heat transfer and warming of the lungs and performed on a simplified geometry of an adult human body and airway from the pharynx to the lungs. Results: The simulations were run over a range of values for blood perfusion rate, which was a parameter expected to have high influence in overall heat transfer, since the heat capacity and density remain almost constant. The simulation results show a temperature distribution which agrees with the expected clinical experience, with the skin surface at a lower temperature than the rest of the body due to convective cooling in a typical hospital environment. The highest temperature in this case is the device warming water temperature, and that heat diffuses by conduction to the nearby tissues, including the air flowing in the airways. At the range of blood perfusion investigated, maximum lung temperature ranged from 37.6°C to 38.6°C. Conclusions: The provision of core warming via commercially available technology currently utilized in the intensive care unit, emergency department, and operating room can increase regional temperature of lung tissue and airway passages. This warming may offer an innovative approach to treating infectious diseases from viral illnesses such as COVID-19, while avoiding the arrhythmogenic complications of currently used pharmaceutical treatments.
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