Duration Of Energy Application Research Articles

Thermal Processes in Bile Ducts During Laparoscopic Cholecystectomy with Monopolar Instruments. Experimental Study Using Real-Time Intraluminal and Surface Thermography.

Introduction. A significant rate of complications during laparoscopic cholecystectomy (LC) occurs due to thermal injury caused by monopolar electrosurgery (MES) equipment. Most of them manifest weeks and months after surgery with the common bile duct (CBD) and large duodenal papilla strictures, some in the early postoperative period with bile leaks. Objective. To study thermal processes occurring in the lumen and on the surface of the bile ducts during monopolar coagulation in a porcine model of LC. Methods. The temperature of the bile ducts was measured using instrumentation consisted of biliary stent with temperature sensors, which was inserted in the porcine CBD, signal amplifier, and current sense transformer. Surface temperature was measured with a scientific grade thermal camera. Cholecystectomy was performed using a standard "critical view of safety" (CVS) approach with 5mm monopolar laparoscopic instruments. Results. Application of MES caused significant tissue heating. Lateral thermal spread and the rate of tissue heating depended on the duration of energy application and the initial tissue temperature. In 5 out of 6 experiments, the intraluminal temperature rose up to the critical threshold, and the exposure time ranged from 54 to 560seconds. A sensor positioned at the papilla site was heated in all the experiments but still below the cell damage inducing threshold. The analysis of thermographic charts revealed the presence of the "current channeling" effect and the pedicle effect. Conclusion. There is a possibility of a direct and delayed thermal injury to the bile ducts during LC.

Intraluminal Esophageal Temperature Monitoring Using the Circa S-Cath™ Temperature Probe to Guide Left Atrial Ablation in Patients with Atrial Fibrillation.

Radiofrequency catheter ablation is a common treatment for atrial fibrillation (AF), during which thermal esophageal injury may rarely occur and lead to an atrio-esophageal fistula. Therefore, we studied the utility of the Circa S-Cath™ multi-sensor luminal esophageal temperature (LET) probe to prevent esophageal thermal injury. Thirty-six patients, enrolled prospectively, underwent circumferential or segmental pulmonary vein isolation for treatment of AF. A maximum ablation electrode temperature of 42ºC was programmed for automatic power delivery cutoff. In addition, energy delivery was manually discontinued when the maximum LET on any sensor of the probe rose abruptly (i.e. ˃0.2ºC) or exceeded 39º C. Esophagoscopy was performed immediately after ablation in 18 patients (with the temperature probe still in place) and at approximately 24 hours after ablation in 18 patients. Esophageal lesions were classified as likely traumatic or thermally related. Of the 36 patients enrolled in the study, 21 had persistent and 15 had paroxysmal AF, average LVEF 57±16% and CHA2DS2VASc score 1.6±1.2 (range 0-4). Average maximum LET was 37.8±1.4ºC, power delivery 31.1±8 watts and ablation electrode temperature 36.4±4.1ºC. Average maximum contact force was 44.5±20.5 grams where measured. Only 1 patient (<3%) had an esophageal lesion that could potentially represent thermal injury and 4 patients (11.1%) had minor traumatic mechanical injury. LET guided titration of power and duration of energy application, using an insulated multi-sensor esophageal temperature probe, is associated with a low risk of esophageal thermal injury during AF ablation. In only rare cases, LET monitoring resulted in the need to manipulate the esophagus to avoid unacceptable temperature rises, that could not be achieved by adjustment of power and duration of energy application.

P981Comparison of automark utilization and lesion metric target during paroxysmal atrial fibrillation ablation with a contact force-sensing ablation catheter: European and U.S. multicenter Experiences

Abstract Background Accurate delivery of transmural lesion is associated with improved durability of pulmonary vein isolation and reduced reconduction. Lesion quality depends on multiple parameters such as radiofrequency power, tissue-catheter contact, duration of energy application, and catheter tip temperature. Consequently, energy delivery parameters vary based on individual operators’ preferences and procedural needs. Purpose To characterize and compare the utilization of automated lesion marking feature and lesion delivery parameters used during paroxysmal atrial fibrillation ablation performed with a magnetic sensor enabled contact force-sensing catheter across European and U.S. centers. Methods Procedural data were prospectively collected in clinical cases performed with a new magnetic sensor enabled, contact force ablation catheter within the first 6 months of use at participating centers in Europe and the U.S. Use of bidirectional CF catheters, steerable sheaths, automated lesion marking software and associated lesion delivery parameters during paroxysmal atrial fibrillation ablation were evaluated. Results A total of 149 cases across 37 centers in 11 European countries, and 112 cases across 31 U.S. centers were analyzed. A bidirectional contact force catheter (56.4% and 90.2%), a steerable sheath (65.8% and 69.6%), and the automated lesion marking module (77.9% and 90.2%) were used in most European and U.S. cases, respectively. The most commonly reported energy delivery parameters were: lesion index (LSI), Force-Time Integral (FTI), and time from European cases; LSI, average force, and FTI for U.S. cases (Table). Target LSI values were recorded for 126 cases in Europe and 34 in the U.S, ranging from 3 to 6. In anterior/roof segments, most common LSI target values for anterior/roof and posterior/inferior segments were 6 (42.9%) and 5 (51.2%) in Europe, and 5.5 (44.1%) and 5 (54.5%) in the U.S. PVI was confirmed with an average of 20.3 minutes waiting period (69.1%) for European cases and exit block (57.1%) in U.S. cases. First pass PVI were 67.1% and 74.4% for European and U.S. cases, respectively. Conclusion Energy delivery parameters and PVI confirmation method varied considerably by geography during paroxysmal atrial fibrillation ablation using the magnetic sensor enabled, contact force ablation catheter. Further study on efficacy implication on these differences in practice should be examined. Energy delivery parameters used Paroxysmal AF N LSI FTI Time Imp Drop Avg Force Other N/A Europe 149 44.0 % 13.4 % 7.0 % 6.0 % 2.4 % 1.0 % 26.2 % U.S. 112 31.2% 17.9 % 6.2 % 8.0 % 23.2 % 11.7 % 1.8 % Energy delivery parameters used in paroxysmal AF ablation in Europe and U.S.

Contrast-enhanced ultrasound-guided percutaneous microwave ablation of renal cell carcinoma that is inconspicuous on conventional ultrasound

Purpose: This study was designed to determine the safety, effectiveness and feasibility of contrast-enhanced ultrasound (CEUS)-guided percutaneous microwave ablation (MWA) of renal cell carcinoma (RCC) that is inconspicuous on conventional ultrasound (US).Materials and methods: A total of 32 RCC nodules in 29 patients (23 men and 6 women) were treated with CEUS-guided percutaneous MWA between January 2010 and September 2014. The median maximum diameter of the nodules was 2.4 cm (interquartile range: 1.8–2.9 cm). The US contrast agent was SonoVue, a second-generation contrast agent. CEUS was applied before the needle was inserted into the tumour, and percutaneous MWA was performed under CEUS-guidance.Results: In total 31 tumours were successfully visualised via CEUS using 1–2 (1.0–2.0 mL) contrast agent injections, and percutaneous MWA was performed under CEUS-guidance. The technical success rate of CEUS-guided percutaneous MWA of RCC was 96.9% (31/32). The mean number of sessions of CEUS-guided percutaneous MWA for each tumour was 1.2 ± 0.4. The mean duration of energy application for each tumour was 7.3 ± 2.7 min. All patients were followed up for 3–71 months (median 17 months) to observe the therapeutic effects and complications. The therapeutic effects were assessed at follow-up with computed tomography (CT) or magnetic resonance imaging (MRI) and CEUS. There was no local tumour progression and the technique effectiveness rate was 100% (31/31). The complications rate was 6.5% and the major complications rate was 3.2%. We observed one case of pleural effusion and one case of renal subcapsular haemorrhage after the percutaneous MWA procedures.Conclusion: CEUS-guided percutaneous MWA is a safe, efficient and feasible therapy for patients with RCCs inconspicuous on conventional US.

Reporting Standards for Percutaneous Thermal Ablation of Renal Cell Carcinoma

WITH the increasing incidence of renal cell carcinoma (RCC) in the United States and the increasing proportion of patients with tumors detected at an early stage (1–5), nephron-sparing approaches are becoming more popular. These alternatives to radical nephrectomy include partial nephrectomy, wedge resection, and, more recently, in situ thermal ablation. Five-year survival rates after partial nephrectomy are equivalent to those after radical nephrectomy (6–8), supporting the rationale of in situ tumor destruction to further reduce morbidity and invasiveness. In situ thermal destruction of RCC uses techniques that destroy tumor tissue through heating (eg, radiofrequency [RF] ablation, microwave ablation, laser interstitial therapy, high-intensity focused ultrasound [US]) or freezing (eg, cryotherapy). Each of these techniques relies on controlled energy delivery to minimize collateral damage to normal renal parenchyma and other surrounding structures. In the United States, RF ablation and cryoablation are currently the most widely used techniques for in situ RCC destruction. Thermal ablation of RCC may be performed percutaneously, laparoscopically, or through open surgery. Our current understanding of the role of percutaneous thermal ablation in the management of primary RCC is limited by a paucity of prospective studies (9,10). Given the relative newness of this technology, most series to date report short-term or midterm outcomes, with no reports extending to 5 years of survival outcomes. No randomized trials have been performed to date comparing thermal ablation against a gold standard (ie, partial nephrectomy) or against other thermal ablation techniques. The optimal size range of RCC amenable to thermal ablation has not been clearly defined and is closely related to anatomic factors that influence the ability to deposit sufficient thermal dose to coagulate tissue, including proximity to major vessels and the urinary collecting system, which can act as a heat sink. The kidney has approximately four times the blood flow of the liver, so convective heat loss during thermal ablation is potentially significant (11). The role of percutaneous thermal ablation compared with laparoscopic or open thermal ablation also remains a topic of controversy. The combination of thermal ablation with other imageguided therapies (eg, transcatheter embolization) and adjuvant therapies such as chemotherapy and antiangiogenic agents for larger RCCs in patients who are poor operative candidates is another potential use of this technique. Although most recent reports of percutaneous RCC ablation have involved RF ablation, other ablation technologies are now available with percutaneous applicators (eg, cryoablation, microwave, laser interstitial therapy), and reporting standards should be uniform for all forms of energy-based ablation. This document provides recommended reporting standards for physicians performing percutaneous thermal ablation of primary RCC and will serve as a template in the design of clinical trials to further evaluate this technology. From the Section of Vascular and Interventional Radiology, Department of Radiology (T.W.I.C.), New York University School of Medicine, New York, New York; Department of Radiology (S.F.M.), University of Western Ontario, Peterborough Regional Health Center, Peterborough, Ontario, Canada; Department of Radiology, Gastrointestinal/Genitourinary Division (D.A.G.), Massachusetts General Hospital; Department of Radiology (S.N.G.), Beth Israel Deaconess Medical Center, Boston; Department of Radiology (C.J.G.), Lahey Clinic Medical Center, Burlington; Department of Radiology (D.A.P.), University of Massachusetts Memorial Health Care, Worcester, Massachusetts; Department of Radiology (T.B.K.), University of California San Diego Medical Center, San Diego, California; Department of Radiology (D.S.), The Reading Hospital and Medical Center, Reading, Pennsylvania; and Department of Radiology (J.F.C.), University of Colorado Health Sciences Center, Denver, Colorado. Received June 19, 2006; revision requested June 19; final revision received June 29; and accepted July 3. Address correspondence to T.W.I.C., c/o Tricia McClenny, Society of Interventional Radiology, 3975 Fair Ridge Dr, Suite 400 North, Fairfax, VA 22033; E-mail: mcclenny@sirweb.org

Image-guided radiofrequency ablation of Bosniak category III or IV cystic renal tumors: initial clinical experience

The purpose of this study was to assess the efficacy of image-guided radiofrequency (RF) ablation of cystic renal tumors. Between November 2005 and August 2007, computed tomography (CT) or ultrasound-guided RF ablation was performed in nine patients with 14 Bosniak category III (n = 5) or IV (n = 9) cystic renal tumors using an internally cooled RF ablation system. We evaluated the number of sessions, cycles and duration of energy application, treatment results, lesion size change, and complications. Together the cystic renal tumors required 15 sessions and 23 cycles of energy application. The duration of energy application per one tumor ablation ranged from 1 to 12 min (mean 6 min). The last follow-up CT indicated complete coagulation of 14/14 (100%) lesions. None of these tumors had recurred within 1-19 months (mean 8 months). The maximum diameter of the cystic renal tumors was significantly reduced from 2.5 +/- 0.6 cm before ablation to 1.7 +/- 0.7 cm at the last follow-up CT (P < 0.01). Complications were pneumothorax (n = 2), inguinal paresthesia (n = 1), and arteriovenous fistula (n = 1). Image-guided RF ablation is an effective treatment for Bosniak category III or IV cystic renal tumors, which might need relatively shorter duration of energy application than purely solid renal tumors of the same size.

The Evolution of Platelet Aggregability in Patients Undergoing Catheter Ablation for Supraventricular Tachycardia with Radiofrequency Energy: The Role of Antiplatelet Therapy

Forty-two consecutive patients were checked for profiles of platelet aggregability before, during, and 10 and 30 minutes after catheter ablation. They were randomized into Group A (n = 20) who accepted intravenous aspirin (in 0.015 g/kg body weight) and Group P (n = 22) who accepted only placebo treatment. Blood samples were drawn from ascending aorta (Ao) and main pulmonary artery (MPA) simultaneously at each time period. In Group P, the EC50 of substrate induced platelet aggregability decreases significantly during (for ADP, from 1.72 to 0.78 mumol/L for samples from Ao, P < 0.0001; and from 1.68 to 0.69 mumol/L for MPA, P < 0.0001; for collagen, from 2.26 to 1.34 micrograms/mL for Ao, P < 0.005, and from 2.40 to 1.64 micrograms/mL, P < 0.0001) and 10 minutes after successful ablation (for ADP, to 0.70 mumol/L for Ao, P < 0.000, and to 0.61 mumol/L for MPA, P < 0.0001; for collagen, to 1.54 micrograms/mL for Ao, P < 0.01, and to 1.63 micrograms/mL, P < 0.0001), and then returned to baseline levels 30 minutes later (all P = NS) compared with comparative baseline levels. The levels of thromboxane B2 (TXB2) had the similar evolution. The evolution of platelet aggregability profiles was not associated with total energy dose, duration of energy application, duration of procedure, impedance, and ablation site. However, there were moderate positive correlations between the TXB2 levels and tip temperatures (r = 0.56, P < 0.05 for Ao and r = 0.65, P < 0.01 for MPA). These results suggest that increased platelet aggregability can occur during and 10 minutes after radiofrequency current ablation and antiplatelet therapy can maintain "flat" response of platelet aggregability to radiofrequency energy, which may provide possible benefits in preventing the occurrence of the complication.

Microwave ablation of canine atrial tachycardia induced by aconitine

We tested the efficacy of microwave-frequency energy for ablating atrial tachycardia in eight open-chest dogs. Five other dogs served as controls. Atrial tachycardia was induced by direct application of aconitine crystals to the epicardial atrial surface or by injection of aconitine solution (0.15 mg/ml) into the right or left atrial myocardium. Atrial tachycardias (n = 15) developed at a cycle length of 253 +/- 64 msec or within 245 +/- 116 sec after topical application or injection of aconitine. Catheter ablation was attempted on 10 atrial tachycardias in 8 experiment dogs by using continuous, unmodulated microwave energy from a 915 MHz frequency signal generator via a 7F helical or whip antenna catheter. Successful ablation was defined as conversion of atrial tachycardia to sinus rhythm during delivery of microwave energy and maintenance of sinus rhythm for > 5 minutes after termination of energy delivery. All 10 atrial tachycardias were successfully ablated by 2.3 +/- 1.6 applications of microwave energy for each atrial tachycardia induced. Forward microwave power level was 50.5 +/- 8.1 W, and the duration of energy application was 25.0 +/- 27.6 seconds. Sinus rhythm resumed 9.5 +/- 9.2 seconds after the onset of microwave energy application. After a mean follow-up of 10.4 minutes, seven atrial tachycardias recurred, most likely the result of diffusion of aconitine beyond the perimeter of rhe ablation lesions. Atrial tachycardia did not recur in 3 of 3 dogs that had larger ablation lesion. Gross examination revealed 10 demarcated round or oval transmural lesions in the right or left atrium, ranging from 12.6 to 105.6 mm2 in area.(ABSTRACT TRUNCATED AT 250 WORDS)