Assessment of a novel cryoablation device for the endovascular treatment of cardiac tachyarrhythmias

Abstract

Objectives:Cryoablation is an effective alternative treatment for cardiac arrhythmias offering shortened recovery and reduced side effects. As the use of cryoablation increases, the need for new devices and procedures has emerged. This has been driven by technological limitations including lengthy periods to generate a single lesion (3–5 min), uncertain transmurality, and differential efficacy. Furthermore, due to limited ablation capacity under high heat loads, cryo has had limited success in the treatment of ventricular arrhythmias. To this end, in this study we evaluated a new cryoablation catheter, ICEolate, for the targeted ablation of cardiac tissue.Methods:Performance assessment included calorimetry, freeze zone isothermal distribution characterization and catheter ablation capacity in a submerged, circulating, heat-loaded ex vivo tissue model. A pilot in vivo study was also conducted to assess ablative capacity of the cryocatheter in a fully beating heart.Results:Ex vivo studies demonstrated ice formation at the tip of a cryocatheter within 5 s and a tip temperature of ~−150°C within 10 s. The device repeatedly generated freeze zones of 2 cm × 3 cm in less than 2 min. Tissue model studies revealed the generation of a full thickness (5–10 mm) cryogenic lesion within 1 min with an opposite (transmural) surface temperature of <−60°C under a circulating 37°C heat load. Pilot in vivo studies demonstrated the delivery of an ablative “dose,” producing a continuous full thickness transmural linear lesion in <60 s at both atrial and ventricular sites.Conclusion:These studies suggest that the supercritical nitrogen cryodevice and ICEolate cryocatheter may provide for rapid, effective, controllable freezing of targeted tissue. The ablative power, speed, and directional freeze characteristics also offer the potential of improved safety via a reduction in procedural time compared to current cryoablation devices. These technological developments may open new avenues for the application of cryo to treat other cardiac arrhythmogenic disorders.

Evaluation of a new epicardial cryoablation system for the treatment of Cardiac Tachyarrhythmias

“…As such, the use of ex vivo models to assess the performance characteristics of thermal ablation devices, such as cryoablation devices and probes, is important. Serving as a comparative standard, studies have also shown that the depth of penetration of the critical -20°C and -40°C isotherms is an important indicator of ablative success both ex vivo and in vitro (24,(53)(54)(55)59,62,65,66) While serving as a good comparative standard, the model in which the isotherm penetration is assessed can significantly impact results. For example, at a given temperature, agarose and ultrasound gel models provide for more favorable isotherm penetration than water baths.…”

“…A new cryoablation probe, which utilizes SCN, designed to deliver a rapid, controlled ultra-cold ablative dose to a target region has been developed. Due to the increased heat extraction capability of SCN compared to argon and nitrous oxide cryogens, SCN also offers the potential to deliver ablative doses deep into tissue while exposed to high heat loads, such as blood flow in a fully beating heart (58,61,62) In this study we utilized a series of ex vivo models to assess and characterize system performance. Further, these studies were also designed to describe a series of bench testing model systems which could potentially serve as reference standards for pre-clinical and clinical study development and protocol optimization.…”

“…The data presented herein suggests that the SCN epicardial cryoprobe provides for the rapid delivery of an effective cryoablative dose to the target tissue using the ex vivo models evaluated. The data demonstrate that the delivery of a "thermal dose" of -30°C [59,[60][61][62][63][64][65][66][67][68] across tissue ranging from 5 mm to 1 cm in thickness under high (37°C) circulating heat loads in less than 2 minutes. Analysis of the thermal spread of the lethal temperatures during a 2-minute freeze was limited to within 5 mm of the probe surface thereby resulting in the creation of a defined linear ablation zone.…”

“…Studies have shown that SCN offers the ability to overcome the limitations of current Joule-Tompson (JT) based cryoablation devices by delivering greater work capacity via its liquid-like heat extraction properties which are more effective than gas [61][62][63][64]. This enhanced heat extraction capacity offers the potential to deliver ultra-cold freeze temperatures deep into tissue under high heat load conditions, such as those experienced when utilizing cryoablation in cardiac ablation settings.…”

Evaluation of a Novel Cystoscopic Compatible Cryocatheter for the Treatment of Bladder Cancer

“…For cooling power evaluations of the prototype, FrostBite cryocatheter, a starting water temperature of 32 • C ± 1 • C was used. This temperature was selected due to previous testing (not shown) that showed ice formation at these temperatures in the calorimetry vessel to be minimal (<1 mm diameter) [44,48]. At warmer temperatures, no ice was observed indicating inefficient flow (complete boiling) of the cryogen.…”