Cryoablation Device Research Articles

P12 : Assessment of SCN and argon cryoablation devices in an in vivo-like 3-D tissue engineered prostate and renal cancer model

An understanding of the thermal gradient within the tissue during cryoablation is important to assure delivery of an “ablative dose” throughout the targeted region. Ablative dose is generally defined as freezing below −20 °C or −40 °C (cancer-type dependent), to assure complete lethality or risk an increased chance of cancer recurrence. Achieving this currently requires a significant amount of non-targeted tissue frozen to > −40 °C for a prolonged interval. Volumetrically, the amount of tissue exposed to > −40 °C, iceball periphery, exceed that of the targeted area. As such, a significant amount of non-targeted tissue is destroyed resulting in collateral damage and post-procedural complications. Given this, while cryoablation is an effective therapeutic option,there is a need for continued procedural improvement by providing quicker and more precise delivery of an “ablative dose” to improve targeted eradication with reducing collateral tissue damage. In an effort to improve cryoablation efficacy, a new cryodevice utilizing supercritical nitrogen (SCN) has been developed which has been reported to rapidly and precisely deliver a highly lethal “cryoablative dose”. In this study we investigated SCN ablative capacity using an in vivo like tissue engineered prostate (pTEM) and renal (rTEM) cancer model. Analysis of the lethal zones created by SCN following a shortened 5/5/5 min freeze/thaw/freeze protocol (SCN5/5/5) using 1.8 mm × 3 cm and 2.0 mm × 4 cm cryoprobes were conducted and compared to those created following the standard Argon-based 10/5/10 min protocol (Ar10/5/10). Ar10/10/10 data was compiled from both the EndoCare V-Probe (direct testing) and Galil IceEdge2.4 probe (literature report comparison). The objective was to determine if SCN could provide equivalent, or increased, cancer cell destruction in less time with smaller probes in a smaller frozen volume supporting delivery of a more lethal cryogenic insult. Assessment following SCN5/5/5 freezing of the TEM’s revealed the formation of a 3.1 cm and 3.9 cm diameter iceball following the 1st and 2nd freeze, respectively, whereas Ar10/5/10 yielded an average diameter of 3.7 cm and 4.4 cm, respectively. Volumetric comparison revealed the SCN yielded a ∼23% smaller iceball (30.1 cm3 vs. 38.8 cm3, respectively). Isothermal assessment demonstrated deeper penetration of the −40 °C isotherm with SCN compared to Ar yielding a steeper thermal gradient within the tissue (SCN vs. Ar; pTEM = 2.1 cm vs. 1.8 cm and rTEM = 2.02 cm vs. 1.87 cm). Assessment of cell death revealed similar outcomes between the protocols (pTEM = 3.0 cm and rTEM = 3.8 cm lethal zone). Correlation of cell destruction to frozen volume demonstrated SCN yielded a 30% (pTEM) and 50% (rTEM) increase in lethality compared to Ar. The results of this study suggest that SCN provides a more lethal cryogenic insult within the frozen mass thereby resulting in improved cancer cell destruction compared to that attained with commercially available Ar. Further, SCN allowed for a reduction in probe size and procedure time while decreasing the level of damage to surrounding non-targeted tissue. As such, through the delivery of more lethal (colder) ice in a more compact frozen tissue mass, a reduction in procedure time, risk of reoccurrence and damage to non-targeted tissues, such as the neurovascular bundles, collecting ducts, rectum, etc., may be achieved.

Prospective Assessment of the CryoMaze Procedure With Continuous Outpatient Telemetry in 136 Patients

Only 40% of patients with atrial fibrillation (AF) undergoing cardiac surgery are treated with surgical AF correction. We prospectively studied endocardial cryoablation of the Cox-maze III lesion set following prespecified rhythm assessment with outpatient telemetry. Between 2007 and 2011, 136 patients underwent surgical AF correction using an argon-powered cryoablation device. Patients wore continuous electrocardiogram monitoring prior to and at 6, 12, and 24 months after surgery. The average length of monitoring was 6.5±1 days prior to surgery and 11±4 days at each time point after surgery. Patients were assessed for cardiac rhythm, interval cardioversion or ablation procedures, pacemaker placement, and the use of warfarin or antiarrhythmic medications. The primary endpoint of this study was freedom from AF at 1 year. Mean patient age was 66±12 years, 50% (69 of 138) were male and 41% (55 of 134) had persistent AF. CryoMaze was done in conjunction with mitral valve operation in 95% (131 of 138) and other procedures in 41% (56 of 138). Follow-up was 96% complete at 1 year and 90% at 2 years. Freedom from AF was 76% at 1 year. Perioperative mortality and stroke rates were both 1.5% (2 of 138). Perioperative pacemaker implantation was required in 7% (9 of 136). In univariate analysis, younger age, female gender, decreased height and weight, smaller preoperative and postoperative left atrial diameter, intermittent AF, and freedom from AF at discharge were associated with freedom from AF at 1 year. Actuarial 2- and 4-year (Kaplan-Meier) survival were 93% and 80%, respectively. The CryoMaze procedure is safe and is associated with 76% freedom from AF at 1 year.

A Novel Minimally Invasive Endometrial Cryoablation Device: Validation in Extirpated Human Uteri

A Novel Minimally Invasive Endometrial Cryoablation Device: Validation in Extirpated Human Uteri

Development of the closed-loop Joule-Thomson cryoablation device for long area cooling

Cryoablation device is a surgical instrument to produce the cooling effect to destroy detrimental biological tissue by utilizing low temperature around 110 K. Usually, this device has the concentrated cooling region, so that it is suitable for concentrated and thick target. Accordingly, it is hard to apply this device for the target which is distributed and thin target. In this study, the design procedure of a closed-loop cryoablation device with multiple J-T expansion part is developed for the treatment of incompetent of great saphenous vein. The developed cyoablation device is designed with the analysis of 1-dimensional (1-D) bio-heat equation. The energy balance is considered to determine the minimum mass flow rate of refrigerant for consecutive flow boiling to develop the uniform cooling temperature. Azeotropic mixed refrigerant R410A and zeotropic mixed refrigerant (MR) of R22 (CHClF2) and R23 (CHF3) are utilized as operating fluids of the developed cryoablation device to form the sufficient temperature and to verify the quality of the inside of cryoablation probe. The experimental results of R410A and the zeotropic MR show the temperature non-uniformity over the range are 244.8 K ±2.7 K and 239.8 K ±4.7 K respectively. The experimental results demonstrate that the probe experiences the consecutive flow boiling over the target range of 200 mm.

41. Development of a novel cryoablation device for the treatment of atrial fibrillation

Cryoablation is an effective minimally invasive therapy for the treatment of atrial fibrillation offering patients a quicker recovery and reduced side effects. As the use of cryoablation increases, a need for the development of more powerful cryoablation devices has emerged. This need has been driven by technological limitations and early clinical outcomes, including lengthy periods to generate a single lesion (3–5 min), uncertain transmurality and differential efficacy. As such, we have developed a novel cryogenic device (LEM) for the targeted ablation of cardiac tissue to treat atrial fibrillation (AF). The LEM technology employs liquid nitrogen (LN 2 ) (−196 °C) in a supercritical state to allow for the rapid and controlled application of ultra cold temperatures and efficient freezing of targeted tissue. Preliminary engineering and in vivo studies were conducted using 11 French flexible probes with 2–10 cm freeze zones. Test conditions included warm (37 °C) water bath, heat load tissue and an in vivo canine model. Engineering research studies demonstrated ice formation at the tip of a cryoprobe within 5 s and achieved a tip temperature of <−150 °C within 10 s. The LEM device repeatedly generated ice balls of 30 mm × 40mm in less than 2 min in the water bath system. Heat load tissue model studies revealed the generation of a full thickness (8 mm), 2–10 cm long cryogenic lesions (catheter/cryoprobe freeze zone dependent) within 1 min, achieving an opposite surface temperature of <−100 °C. Preliminary animal studies demonstrated the delivery of an ablative cryogenic “dose”, producing a contiguous transmural linear lesion in less than 90 s. These studies confirm that the LEM supercritical nitrogen technology provides for rapid, effective, controllable freezing of targeted tissue. The ablative power, speed and directional freeze characteristics of the LEM system also offers the potential of improved safety via a reduction in procedural time compared to current cryoablation devices. Further, these technological developments may open new avenues for the application of cryo to treat other cardiac arrhythmogenic disorders.

Coronary Artery Spasm After Cryo Maze III Procedure

The Cox Maze III procedure has been simplified with the availability of tissue ablation devices; however, complications related to their use are recognized. We report a case of 45-year-old woman who underwent mitral valve repair and concomitant Cryo-Maze procedure. She had reversible right coronary artery spasm develop after the procedure demonstrated by ST-segment elevation changes and coronary angiography, which was reversed with intracoronary nitroglycerin. The region of spasm suggested it as a consequence of proximity of the right coronary artery to the right atrial ablation lines.

Mid-term results of endoscopic mitral valve repair in combination with endocardial or epicardial ablation

Concomitant ablative therapy for atrial fibrillation can be effective at converting patients to normal sinus rhythm and at maintaining a regular rhythm for at least 5 years. We provide herein a comparison of an endocardial approach using Cryoablation with an epicardial approach using a suction-based RF ablation technology. Between February 2004 and January 2009, 325 patients underwent an endoscopic mitral valve repair. Of those patients, 112 (35%) had a history of atrial fibrillation prior to the procedure, all of whom underwent a concomitant ablation procedure. The first group of 78 concomitant ablation patients underwent a left-sided endocardial ablation procedure using a Cryoablation device. The second group of 34 ablation patients underwent a left-sided epicardial ablation procedure using an internally cooled monopolar RF device. No significant differences existed between groups in the preoperative data. All ablated patients were treated by the same Amiodarone protocol. Patients were followed for a minimum of 6 months for determining each ablated patient's rhythm, medication use, and overall health status. The AF-free rates of group I and group II patients were statistically equivalent for both ablation groups at all evaluation time points. None of the 112 patients treated with endoscopic mitral valve repair and ablative therapy experienced a specific patient injury attributable to ablation; no ablated patients died in hospital following the procedure; there were no esophageal perforations and no coronary artery stenosis due to the ablations in either ablation group. The rate of patients without AF was 74% in group I and 82% in group II in the 6-month follow-up. The group I pacemaker implantation rate of 14% was significantly higher than non-ablated group (4.7%), but the group II rate of 5.9% observed did not differ significantly from the non-ablated group. It was shown with our results that one succeeds with the en bloc-ablation in treating patients with different kinds of atrial fibrillation with concurrent intervention in the mitral valve reliably and with a high rate. The combination of this procedure with endocardial interventional ablation technologies can possibly develop to a promising strategy in the hybrid therapy of the isolated chronic atrial fibrillation as a standalone procedure.

111. Development of a novel cryoablation device for the treatment of atrial fibrillation

111. Development of a novel cryoablation device for the treatment of atrial fibrillation

Outcomes for Surgical Treatment of Atrial Fibrillation Using Cryoablation During Concomitant Cardiac Procedures

Surgical treatment of atrial fibrillation (AF) with heat-based therapies has been associated with a high rate of arrhythmia recurrence. We studied the short-term to medium-term outcomes with a unique biatrial linear ablation procedure for AF treatment using an argon-based cryoablation device during concomitant cardiac operations. Between March 2005 and July 2008, 57 patients (47% men) with problematic AF underwent a linear endocardial ablation procedure (Star pattern) using the flexible argon-based cryoablation probe during concomitant cardiac operations. Procedures were performed with valve or coronary operations, including mitral valve replacement (25%), mitral valve repair (16%), coronary artery bypass grafts (21%), and congenital heart surgery (8%). Atrial fibrillation was persistent or long-standing persistent in 50.9% of patients. Kaplan-Meier survival curves (with the standard error) demonstrated 91% (3.9%) of patients were still free of their first recurrence at 6 months, 81% (5.6%) at 12 months, and 70% (6.8%) at 24 months. Time to first recurrence was not significantly associated with age (p = 0.47), gender (p = 0.52), or type of AF (p = 0.69). There were no complications attributed to the cryoablation procedure. There was one in-hospital death and one death after discharge. Twelve patients (21%) required permanent pacemaker implantation postoperatively. There were no early or late thromboembolic events. This study demonstrated the medium-term efficacy of cryoablation with a unique biatrial pattern of linear lesions for the treatment of AF during a concomitant cardiac operation. Short-term to medium-term outcomes were at least equivalent to those reported for other energy modalities.

Intraoperative ablation of atrial fibrillation - replication of the Cox's maze III procedure with re-usable radiofrequency and cryoablation devices

The cut and sew Cox's maze III procedure is time-consuming. Therefore, various energy sources have been used for ablation, to replace the cut and sew technique. We have used the bipolar radiofrequency output of a standard electrosurgical generator with re-usable forceps for replicating the Cox's maze III procedure from August 1996. In addition, re-usable nitrous oxide based cryoprobe has been used at the atrioventricular valve annuli and on the coronary sinus. The 85.7% cure rate at one year compares with that for surgical ablation of atrial fibrillation using alternative energy sources.

Outcomes for the Surgical Treatment of Atrial Fibrillation Using Cryoablation During Concomitant Cardiac Procedures

Background. Surgical treatment of atrial fibrillation (AF) with heat-based therapies has been associated with a high rate of arrhythmia recurrence. We studied the short-term to medium-term outcomes with a unique biatrial linear ablation procedure for AF treatment using an argon-based cryoablation device during concomitant cardiac operations. Methods. Between March 2005 and July 2008, 57 patients (47% men) with problematic AF underwent a linear endocardial ablation procedure (Star pattern) using the flexible argon-based cryoablation probe during concomitant cardiac operations. Procedures were performed with valve or coronary operations, including mitral valve replacement (25%), mitral valve repair (16%), coronary artery bypass grafts (21%), and congenital heart surgery (8%). Atrial fibrillation was persistent or long-standing persistent in 50.9% of patients. Results. Kaplan-Meier survival curves (with the standard error) demonstrated 91% (3.9%) of patients were still free of their first recurrence at 6 months, 81% (5.6%) at 12 months, and 70% (6.8%) at 24 months. Time to first recurrence was not significantly associated with age (p 0.47), gender (p 0.52), or type of AF (p 0.69). There were no complications attributed to the cryoablation procedure. There was one in-hospital death and one death after discharge. Twelve patients (21%) required permanent pacemaker implantation postoperatively. There were no early or late thromboembolic events. Conclusions. This study demonstrated the mediumterm efficacy of cryoablation with a unique biatrial pattern of linear lesions for the treatment of AF during a concomitant cardiac operation. Short-term to mediumterm outcomes were at least equivalent to those reported for other energy modalities.

Epicardial beating heart cryoablation using a novel argon-based cryoclamp and linear probe

Epicardial, beating heart cryoablation for the treatment of atrial fibrillation may be limited by heat from intracardiac blood flow. We therefore evaluated the ability to create cryolesions using an argon-based cryoclamp device, which temporarily occludes blood flow and facilitates transmurality. Six mongrel dogs underwent sternotomy. A clamp employing a 10-cm argon-based linear cryoablation device was used epicardially to isolate the pulmonary veins and left atrial appendage. After clamping of lesions, the probe was removed from the cryoclamp device, and the remaining linear lesions, analogous to the Cox maze III, were performed. Pulmonary vein stenosis was evaluated with the use of magnetic resonance imaging. Left atrial function and pulmonary venous flow velocities were assessed with transesophageal echocardiography. Transmurality was confirmed both electrically and histologically. Animals were then put to death at 30 days. All acute and chronic cryoclamp lesions produced conduction block. There was no change in right (RPV) or left pulmonary vein (LPV) diameter on the basis of magnetic resonance imaging at baseline and at planned death (RPV-1, 19.6 +/- 2.9 mm vs 16.9 +/- 2.8 mm, P = .22; RPV-2, 13.2 +/- 2.0 mm vs 11.8 +/- 1.6 mm, P = .22; and LPV, 12.2 +/- 2.4 mm vs 11.2 +/- 1.9 mm, P = .30). Left atrial function and pulmonary venous flow velocities were unchanged. Tissue sections determined transmurality in 93% of cryoclamp lesions and 84% of linear ablations performed with the 10-cm malleable probe. Epicardial application of this cryoclamp device on the beating heart produced transmural lesions, which persisted 30 days. Linear epicardial cryoablation was not as effective as the cryoclamp device at producing consistent transmural lesions. This novel, versatile device may be useful in treating patients with atrial fibrillation on the beating heart without cardiopulmonary bypass.

Hybrid Radiofrequency and Cryoablation Device: Preliminary Results in an Animal Model

To determine whether the simultaneous application of combined bipolar radiofrequency (RF) ablation and cryoablation in a hybrid system produces larger ablation zones than RF or cryoablation alone. Multiple 15-minute ablations were performed in ex vivo bovine liver (n = 167) with a hybrid applicator system with RF ablation alone (0.3-0.7 A), cryoablation alone (3,500 psi, two freeze/thaw cycles), and combined RF/cryoablation (0.4-0.7 A, 1,000-3,500 psi) with use of a novel applicator consisting of two 2.5-cm active bipolar RF poles located on the same 18-gauge needle separated by two embedded cryoablation nozzles. Resultant coagulation diameters were compared with use of analysis of variance for more than three groups or Student t tests for two groups. Confirmation of the optimal parameters of combination RF/cryoablation was performed by reassessing a range of argon pressure (1,000-3,500 psi) and RF current (0.4-0.7 A) in in vivo porcine liver (n = 36). Arrays of two to four RF/cryoablation applicators were also assessed in ex vivo (n = 54) and in vivo (n = 12) liver. In ex vivo liver, simultaneous RF/cryoablation (0.6 A, 3,000 psi) produced 3.6 cm +/- 0.4 of short-axis coagulation. This was significantly larger than that achieved with optimal RF alone or cryoablation alone (1.5 cm +/- 0.3 and 1.6 cm +/- 0.3, respectively; F = 95; P < .01). The coagulation diameter with simultaneous combination RF/cryoablation was related in parabolic fashion to argon pressure and current with a multivariate r(2) of 0.68. For in vivo liver, optimal combination RF/cryoablation achieved 3.3 cm +/- 0.2 of coagulation, which was significantly larger than that achieved with RF alone (1.1 cm +/- 0.1; P < .01) or cryoablation alone (1.1 cm +/- 0.1 and 1.3 cm +/- 0.1; F = 203; P < .01). The greatest contiguous coagulation was achieved with multiple-applicator arrays. For ex vivo liver, short-axis coagulation measured 5.3 cm +/- 0.1, 6.4 cm +/- 0.1, and 7.6 cm +/- 0.1 for two-, three-, and four-applicator arrays, respectively. For in vivo liver, two-, three-, and four-applicator arrays produced 5.1 cm +/- 0.2, 5.8 cm +/- 0.5, and 7.0 cm +/- 0.5 of confluent coagulation, respectively. Simultaneous combination RF and cryoablation with use of a novel applicator design yielded significantly larger zones of coagulation than either modality alone. The large ablation diameters achieved warrant further investigation of the device.

A Randomized Study Comparing Endometrial Cryoablation and Rollerball Electroablation for Treatment of Dysfunctional Uterine Bleeding

Study Objective To determine the effectiveness of endometrial cryoablation in comparison with rollerball electroablation. Design Prospective, randomized study (Canadian Task Force classification I). Setting Ten university and private medical centers in the United States. Patients Two hundred seventy-nine women with menorrhagia due to benign causes. Intervention Endometrial ablation using a Her Option cryoablation device in 193 women and rollerball electroablation in 86. Measurements and Main Results Women treated by cryoablation received significantly less general anesthesia (46%) than those treated by electroablation (92%). Subjects maintained menstrual diaries for at least one cycle before and for 12 months after the procedure. Success was defined as reduction of menstrual bleeding to a score of 75 or less in the absence of retreatment. Success rates in the cryoablation and electroablation groups were 77.3% and 83.8%, respectively. Bleeding declined by 92% and 94%, respectively. Both procedures led to significant improvements in a broad range of symptoms including menses-related pain, mood, and overall improvement in quality of life. Conclusion Endometrial cryoablation is a safe and effective procedure in treatment of dysfunctional uterine bleeding. Its advantages include technical ease of performance, direct ultrasonographic view of depth of ablation, little anesthetic, and avoidance of potential complications related to distention media.