射频消融与微波消融对离体牛肝作用的实验研究

目的：比较射频消融与微波消融对离体牛肝的作用效果。方法实验分为射频组与微波组,分别使用Cool-tip射频针与冷循环微波刀,均采用单针单次方式消融离体牛肝,比较两组间相同消融时间消融灶纵径、横径及体积。结果消融4、6、8 min,微波组消融灶纵径及体积均大于对应时间射频组消融灶纵径及体积（P＜0.05）,消融10 min,两组消融灶纵径及体积差异均无统计学意义（P＞0.05）;消融4 min,微波消融灶横径大于对应时间射频消融灶横径（P＜0.05）,消融6、8、10 min,两组消融灶横径差异均无统计学意义（P＞0.05）。结论与射频相比较,微波的热效率更高,消融速度更快,但随着消融时间延长,最终两者可取得相近的消融效果。     

Tissue temperatures and lesion size during irrigated tip catheter radiofrequency ablation: an in vitro comparison of temperature-controlled irrigated tip ablation, power-controlled irrigated tip ablation, and standard temperature-controlled ablation

The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced in the power-controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature-controlled irrigated tip ablation, comparing it with standard temperature-controlled ablation and power-controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature-controlled irrigated tip ablation at target temperatures 60 degrees C, 70 degrees C, and 80 degrees C with infusion of 1 mL saline/min were compared with standard temperature-controlled ablation at 70 degrees C and power-controlled irrigated tip ablation at 40 W, and infusion of 20 mL/min. Lesion size and tissue temperatures were significantly higher during all modes of irrigated tip ablation compared with standard temperature-controlled ablation (P < 0.05). Lesion volume correlated positively with tissue temperature (r = 0.87). The maximum recorded tissue temperature was always 1 mm from the ablation electrode and was 67 +/- 4 degrees C for standard ablation and 93 +/- 6 degrees C, 99 +/- 6 degrees C, and 115 +/- 13 degrees C for temperature-controlled irrigated tip ablation at 60 degrees C, 70 degrees C, and 80 degrees C, respectively, and 112 +/- 12 degrees C for power-controlled irrigated tip ablation, which for irrigated tip ablation was significantly higher than tip temperature (P < 0.0001). Crater formation only occurred at tissue temperatures > 100 degrees C. We conclude that irrigated tip catheter ablation increases lesion size and tissue temperatures compared with standard ablation in the temperature-controlled mode at the same or higher target temperatures and in the power-controlled mode. Furthermore, tissue temperature and delivered power are the best indicators of lesion volume during temperature-controlled ablation.     

Paroxysmal atrial fibrillation ablation with the multipolar mapping and ablation catheter (Mesh-Bard)

Pulmonary veins (PVs) ablation is a valid treatment option for atrial fibrillation. The standard approach for PVs isolation usually requires two catheters or an electroanatomical reconstruction of the left atrium. We describe our initial experience with a single device for mapping and ablating in a patient referred to our center for the relapsing of atrial fibrillation 3 years after a previous ablation procedure. The newly available catheter MESH was safe and effective to quickly isolate two reconnected PVs.     

临床路径在房颤射频消融术患者中的应用

目的探讨临床路径在房颤射频消融术患者中的应用效果。方法根据现行的诊疗护理内容,制订房颤射频消融术的临床路径表。选择房颤射频消融术患者180例,依据患者入院顺序分成观察组和对照组。对照组患者按常规进行护理和健康教育指导。观察组患者根据临床路径表进行护理,比较两组患者的平均住院日、满意度、并发症等指标的差异。结果观察组患者平均住院日和平均住院费用明显低于对照组(P0.01),患者满意度和健康知识测评结果优于对照组(P0.01),两组术后并发症的发生率比较差异无统计学意义(P0.05)。结论推广临床路径有助于在保证护理质量的前提下,减少患者住院日和住院费用,减轻患者经济压力,提高满意度。     

Atrial fibrillation ablation using a closed irrigation radiofrequency ablation catheter

Background: Catheter ablation is an effective therapy for symptomatic, medically refractory atrial fibrillation (AF). Open‐irrigated radiofrequency (RF) ablation catheters produce transmural lesions at the cost of increased fluid delivery. In vivo models suggest closed‐irrigated RF catheters create equivalent lesions, but clinical outcomes are limited. Methods: A cohort of 195 sequential patients with symptomatic AF underwent stepwise AF ablation (AFA) using a closed‐irrigation ablation catheter. Recurrence of AF was monitored and outcomes were evaluated using Kaplan–Meier survival analysis and Cox proportional hazards models. Results: Mean age was 59.0 years, 74.9% were male, 56.4% of patients were paroxysmal and mean duration of AF was 5.4 years. Patients had multiple comorbidities including hypertension (76.4%), tobacco abuse (42.1%), diabetes (17.4%), and obesity (mean body mass index 30.8). The median follow‐up was 55.8 weeks. Overall event‐free survival was 73.6% with one ablation and 77.4% after reablation (reablation rate was 8.7%). Median time to recurrence was 26.9 weeks. AF was more likely to recur in patients being treated with antiarrhythmic therapy at the time of last follow‐up (recurrence rate 30.3% with antiarrhythmic drugs, 13.2% without antiarrhythmic drugs; hazard ratio [HR] 2.2, 95% confidence interval [CI] 1.1–4.4, P = 0.024) and in those with a history of AF greater than 2 years duration (HR 2.7, 95% CI 1.1–6.9, P = 0.038). Conclusions: Our study represents the largest cohort of patients receiving AFA with closed‐irrigation ablation catheters. We demonstrate comparable outcomes to those previously reported in studies of open‐irrigation ablation catheters. Given the theoretical benefits of a closed‐irrigation system, a large head‐to‐head comparison using this catheter is warranted. (PACE 2012; 35:506–513)     

MR-guided laser ablation

MR-guided LITT is a safe and effective treatment modality that improves survival in well-selected patients who have liver metastases. A major advantage of MR-guided LITT is that it can be easily performed under local anesthesia in an outpatient setting with a low complication rate.     

Remote magnetic navigation-assisted catheter ablation enhances catheter stability and ablation success with lower catheter temperatures

Background: It has been suggested that remote magnetic navigation (RMN) may provide enhanced catheter stability and substrate contact to aid in ablation. To date, no study has examined this claim. Accordingly, we compared the characteristics of the successful ablation of atrioventricular reentry tachycardia (AVNRT) using RMN with a matched population ablated using a conventional (CON) manual approach.
Methods: Sixteen patients who underwent RMN-assisted ablation of typical AVNRT were matched with 16 patients who had a CON-AVNRT ablation.
Results: All patients had successful slow pathway modification without complication. The mean catheter temperature achieved with the successful ablation was significantly lower with RMN than with CON (42 ± 7°C vs 47 ± 3°C, P ≤ 0.05). Time to junctional tachycardia (JT) was significantly earlier (5.7 ± 4.1 s vs 11.2 ± 8.9 s, P ≤ 0.05) and variation in catheter temperature with the successful ablation (0.89 ± 0.45 vs 1.45 ± 0.49, P < 0.01) was significantly reduced in the RMN group than in the CON group. There was no significant difference between RMN and CON in terms of the total number of lesions and the mean power achieved during the successful lesion.
Conclusions: Although the construction of the ablation catheters is similar, ablations with RMN catheters resulted in a lower mean temperature, earlier time to JT, and less variability of temperature during ablation, suggesting greater catheter stability. This study indicates that ablation with RMN can achieve success with lower catheter temperatures.     

犬左室乳头肌的导管超声消融

背景：近年来的研究表明左室乳头肌在室性心律失常的发生中起到了重要的作用。目的：在经胸超声图像监控下,观察自制的超声消融导管消融动物左室乳头肌的可行性和安全性。方法：普通杂种犬9只,随机分为2组：对照组3只,消融组6只。3％戊巴比妥钠麻醉后于无菌条件下分离其颈动脉并置入8F动脉鞘管,行机械通气并记录体表心电图,导管在经胸超声的引导下达到左心室腔,通过经胸超声图像调整导管与乳头肌的贴靠关系,保持导管与乳头肌贴靠良好,随后以声强50W／cm2、时间60s消融左室乳头肌。结果与结论：所有动物在观察期内均正常存活,乳头肌等解剖结构经胸超声图像显示清楚,并能通过经胸超声图像明确导管与乳头肌的相对位置及贴靠情况,切开动物心肌后,大体可见乳头肌内消融灶与周围正常心肌组织界限清晰,中央区呈白色,绕以淡红色的周边区。光镜下见消融灶与周边组织界线分明,灶内心肌细胞坏死,细胞间隙增宽,大量红细胞浸润。无附壁血栓、心肌灼伤及穿孔和心脏破裂等手术相关并发症。可见在经胸超声的实时监控下,能够实现导管对乳头肌深部组织安全有效的消融。     

Monitoring stiffness changes in lesions after radiofrequency ablation at different temperatures and durations of ablation

The variations in the stiffness or stiffness contrast of lesions resulting from radiofrequency (RF) ablation of canine liver tissue at different temperatures and for different ablation durations at a specified temperature are analyzed. Tissue stiffness, in general, increases with temperature; however, an anomaly exists around 80 degrees C, where the stiffness of the lesion is lower than that of the lesion ablated at 70 degrees C. On the other hand, the stiffness increases monotonically with the duration of ablation. Plots illustrating the ratio of mean strains in normal canine liver tissue to mean strains in ablated thermal lesions demonstrate the variation in the stiffness contrast of the thermal lesions. The contrast-to-noise ratio (CNRe) of the lesions, which serves as an indicator of the detectability of the lesions under the different experimental imaging conditions described above, is also presented. The results presented in this paper show that the elastographic depiction of stiffer thermal lesions is better, in terms of the CNRe parameter. An important criterion in the elastographic depiction of RF-ablated regions of tissue is the trade-off between ablation temperature and duration of ablation. Tissue necrosis can occur either by ablating tissue to high temperatures for short durations or to lower temperatures for longer durations. In this paper, we attempt to characterize the elastographic depiction of thermal lesions under these different experimental conditions. This paper provides results that may be utilized by practitioners of RF ablation to decide the ablation temperature and duration, on the basis of the strain images of normal liver tissue and ablated thermal lesions discussed in this paper.     

Laser procedures for tumour ablation and destruction

Summary

Different lasers can be used in different techniques for tumour ablation and destruction. Thermal or biochemical procedures are also possible. Thermal procedures offer coagulation (in situ coagulation or interstitial coagulation) or vaporisation (recanalisation). Photodynamic therapy (PDT), based on biochemical, intracellular reactions, is helpful in treating premalignant diseases, recurrences or metastases. All procedures allow an endoscopic, percutaneous or open approach.     

Atrial tachycardias following circumferential pulmonary vein ablation: observations during catheter ablation

Circumferential pulmonary vein ablation performing linear lesions around the ostia of the pulmonary veins has been shown to be effective for the treatment of atrial fibrillation. During the follow-up period, persistent atrial tachycardia may occur as a proarrhythmic complication. Only little information is available about the underlying mechanism. In our study, atrial tachycardia following circumferential pulmonary vein ablation was identified in 13 out of 84 consecutive patients (15.5%), as a transient appearance in four and with recurrences for more than 3 months in nine patients (10.7%). Electrophysiological study and ablation was performed in eight cases, revealing common atrial flutter in two, a focal origin secondary to conduction recovery from the pulmonary vein to the left atrium in two and macro reentrant left atrial flutter in four patients. The electrophysiological characteristics demonstrated by electroanatomic activation mapping (CARTO™) and consecutive ablation therapy with a 100% success rate are described and discussed with regard to the literature.     

对比经皮微波消融与射频消融治疗肝癌疗效的Meta分析

目的 对比分析微波消融(MWA)与射频消融(RFA)治疗肝细胞肝癌(HCC)的疗效。方法 对相关电子文献数据库进行检索,筛选并确定2014年5月以前发表的符合纳入及排除标准的有关MWA与RFA治疗HCC疗效对比的随机对照试验(RCTs)、前瞻性及回顾性对比研究。采用固定效应模型或随机效应模型合并相对危险度以及95%可信区间。结果 共纳入8篇文献,总计766例患者。MWA组与RFA组的肿瘤完全消融率、主要并发症发生率、1年及3年总生存率、1年及3年无瘤生存率差异均无统计学意义(P均>0.05)。不同大小HCC亚组分析显示,对于≤5 cm的HCC,MWA组与RFA组肿瘤完全消融率、主要并发症发生率、总生存率及无瘤生存率差异均无统计学意义(P均>0.05)。结论 MWA对于HCC的疗效与RFA相当。随着相关技术的发展,改良后的MWA在今后应用前景可观。     

The biophysics and biomechanics of cryoballoon ablation

Recent clinical and preclinical studies have demonstrated that cryothermal ablation using a balloon catheter (Artic Front®, Medtronic CryoCath LP, Pointe‐Claire, Canada) provides an effective means of achieving pulmonary vein isolation. This review explores the biophysics and biomechanics of cryoballoon ablation. Components of the cryoballoon catheter system are examined, mechanisms of cryothermal injury are summarized, and potential advantages of cryoballoon technology over standard radiofrequency ablation in isolating pulmonary veins are discussed. Practical aspects of biophysics and biomechanics relevant to the clinical electrophysiologist are emphasized, particularly with regards to the selection of the most appropriate cryoballoon catheter and minimizing peri‐procedural complications. (PACE 2012; 35:1162–1168)     

Contrast-agent-enhanced ultrasound thermal ablation

The small thermal lesions induced when using high-intensity focused ultrasound (HIFU) to ablate tumors results in long treatment duration. In this study, the effect of using ultrasound contrast agent (UCA, Definity) to enhance the ultrasound (US) thermal effects and, thus to enlarge the lesion size, was studied in transparent tissue phantoms insonified by 1.85-MHz US with acoustical powers of 28.9 and 40.4 W. The experimental results show that the lesion size depended strongly on the electrical power and the concentration of UCA. UCA also reduced the power required to form a lesion of a certain size by about 30%. However, UCA moved the greatest heating position from the transducer focus, by 2.16 cm for 0.015% UCA at 40.4 W, and with lesions forming at the surface for UCA concentrations higher than 0.1%. An optimal result was obtained when using 0.001% UCA and 28.9-W US, which produced a lesion 12 times larger and an acceptable shift (less than half of the lesion length). UCA can effectively increase the size of the HIFU lesions, but lesion shift should be carefully considered while performing HIFU ablations.     

Tissue temperature-controlled radiofrequency ablation

During radiofrequency energy delivery, the catheter tip temperature can be significantly lower than the tissue temperature. The authors performed tissue temperature-controlled radiofrequency ablation in vitro and evaluated the effects of cooling, electrode to tissue contact, and target tissue temperature on lesion size. Pieces of porcine ventricle were immersed in a bath of isotonic saline solution at 37 degrees C. Radiofrequency energy was controlled by the tissue temperature as measured with a thermocouple needle placed 2 mm beneath the ablation electrode. Radiofrequency power was delivered for 30 seconds and limited to 50 W. A total of 81 radiofrequency ablations was performed with different electrode to tissue contact forces (0.04 N, 0.36 N, and 0.67 N) and target tissue temperatures (50 degrees C, 60 degrees C, and 70 degrees C) using an irrigated (27 ablations, 20 mL/min irrigation flow rate) or a nonirrigated ablation catheter. Twenty-seven nonirrigated applications were performed with fluid flow maintained by the pump of the thermostat and another 27 applications without flow. Every combination was applied three times and the average values were used for evaluation. For tissue target temperatures of 50 degrees C, 60 degrees C, and 70 degrees C, the lesion volume for nonirrigated ablations was on average 21 +/- 8 mm3, 45 +/- 23 mm3, and 109 +/- 45 mm3, respectively, and for irrigated ablations 12 +/- 7 mm3, 37 +/- 20 mm3, and 92 +/- 30 mm3, respectively. In both application groups the lesion size did not correlate with the electrode to tissue contact force. In the nonirrigated ablation group there was no difference in lesion size between the group with fluid flow and those without. Lesion size during tissue temperature-controlled radiofrequency delivery increases with increasing target tissue temperature and becomes independent of flow and electrode to tissue contact.     

Ultrasound-guided biopsy and ablation in the neck

Management and therapy of conditions of the thyroid, parathyroid glands, and cervical lymph nodes have evolved rapidly during the past 15 years. The development and continued improvement of high-resolution ultrasound (US) equipment, US-guided biopsy, and image-guided ablative techniques have fueled this change. These technical improvements and the knowledge and experience gained during this time have decreased the rate of unnecessary surgery in patients with thyroid nodules. They have also allowed more limited neck dissection in patients with parathyroid adenomas and have led to the development of US-guided ablative techniques that have eliminated the need for surgery in some cases. This article reviews the rationale and techniques of US-guided biopsy of the thyroid, parathyroid, and cervical lymph nodes. Established and evolving ablative techniques of these structures are also examined.     

Reflux testing and imaging for endovenous ablation

Endovenous ablation is a newer therapy for treating superficial veins in patients with chronic venous disease. The saphenous veins and their accessory veins can be treated. Radiofrequency and laser energy are used to ablate the veins. Accurate ultrasound mapping is needed to plan and perform these procedures. The length and the number of the veins treated are determined. The diameter of the vein, its distance from the skin, and segments with tortuosity, thrombosis, and anatomic variations are documented. During the procedure the access in the vein, and the introduction of the wire, sheath, catheter, and tumescent anesthesia are done under ultrasound guidance. The success of the procedures and the complications are monitored. In most studies, the failure rate is 10% or less at 2 years, and the prevalence of deep vein thrombosis is less than 3%. Currently, endovenous ablation has become the method of choice for treating superficial veins and it has almost replaced the traditional ligation and stripping.