Cooled Ablation

Research on cooled ablation has been evolving for the last 10 years. Findings and current applications are reviewed. A cooled ablation catheter is approved by the FDA for use in idiopathic ventricular tachycardia (VT) patients, based on data originally submitted by Cardiac Pathways, Inc. This technology has subsequently been used by the clinicians in atrial flutter cases, nonischemic VT, epicardial accessory pathways, and atrial fibrillation. The experience at Johns Hopkins suggests that cooled radiofrequency ablation has utility in a variety of situations and in some instances has come to be the ablation system of choice.     

Catheter Ablation of Atrial Tachycardia Following Atrial Fibrillation Ablation

Atrial tachycardias represent the second front of atrial fibrillation (AF) ablation. They are frequently encountered during the index ablation for patients with persistent AF and are common following ablation of persistent AF, occurring in half of all patients who have had AF successfully terminated. An atrial tachycardia is rightly seen as a failure of AF ablation, as these tachycardias are poorly tolerated by patients. This article describes a simple, practical approach to diagnosis and ablation of these atrial tachycardias.     

Temperature Monitoring in Radiofrequency Catheter Ablation of Atrial Flutter Using the Linear Ablation Technique

Temperature Monitoring of Ablation. Introduction: Information about temperature and impedance monitoring during radiofrequency catheter linear ablation of atrial flutter bas not been reported. We proposed that a radiofrequency catheter ablation system using a closed-loop temperature control model could decrease the incidence of coagulum formation and shorten the radiation exposure and procedure times compared with those found in a power control model.
Methods and Results: Forty patients (8 women and 32 men; mean age 64 ± 7 years) with atrial flutter were referred for radiofrequency ablation. The patients were randomized into two groups: group I patients underwent radiofrequency catheter linear ablation of atrial flutter using a power control of energy output model; and group II patients underwent the closed-loop temperature control model with a target electrode temperature of 70°C. As compared with group II, group I patients bad a higher incidence of coagulum formation (12% vs 2%, P < 0.05), temperature shutdown (11% vs 0%, P < 0.01), and impedance shutdown (16% vs 3%, P < 0.01), more radiofrequency applications (7 ± 3 vs 4 ± 2, P < 0.01), and longer procedure time (100 ± 25 vs 75 ± 23 minutes, P < 0.05) and radiation exposure time (31 ± 10 vs 20 ± 7 minutes, P < 0.05) required for successful ablation. Larger deviations of temperature (9.0°± 2.4°C vs 5.0°± 1.2°C, P < 0.0001) and impedance (9.2 ± 2.6 ω vs 5.3 ± 1.6 ω, P < 0.0001) were also found in group I patients compared with those in group II.
Conclusions : This study demonstrated that a closed-loop temperature control model could facilitate the effects of radiofrequency catheter ablation of the atrial flutter circuit by decreasing coagulum formation, temperature and impedance shutdown, and procedure and radiation exposure times.     

射频消蚀术并发症及其防治

３４４例射频消蚀术中出现并发症９例（２．６％），其中心脏破裂致死１例（０．３％），ＩＩＩ度房室传导阻滞３例（０．９％），心室颤动２例（０．６％），主动脉瓣损伤、大头导管误入冠状动脉引起冠状动脉一过性缺血及股动脉术后出血形成巨大皮下血肿各１例。对各种并发症的防治进行了分析讨论。提出经验不足是产生并发症的主要原因。     

对比观察射频消融右房后位峡部和间隔峡部治疗典型心房扑动的疗效

对比观察射频消融右房后位峡部和间隔峡部治疗心房扑动 (简称房扑 )两种方法的疗效。 41例房扑患者随机分为后位峡部组 ( 18例 )和间隔峡部组 ( 2 3例 ) ,消融线径分别为三尖瓣环—下腔静脉和三尖瓣环—欧氏嵴。成功消融终点为房扑不能诱发和峡部呈完全性双向阻滞。结果 :40例消融成功 ( 97.6 % ) ,无并发症。后位峡部组 3例和间隔峡部组 2例在首选消融方法失败后 ,改用另一种消融方法获得成功。两组患者的放电次数和手术时间均无显著性差异。平均随访 12 .4± 6 .8个月 ,在后位峡部消融成功者中 ,有 2例房扑复发。结论 :射频消融右房后位峡部和间隔峡部治疗房扑均安全有效 ,两种方法互补可以提高消融的成功率     

Endoscopic Radiofrequency Ablation of the Pancreas

Radiofrequency ablation (RFA) is a well-established technique to ablate dysplastic and neoplastic tissue via local thermal coagulative necrosis. Despite the widespread use in management of several cancers, the application of RFA in pancreas has been limited due to the increased risks of complications from the increased sensitivity of pancreatic tissue to thermal injury and proximity to vascular and biliary structures. RFA has been successfully used during laparotomy for locally advanced pancreatic carcinoma but requires an invasive approach. Endoscopic ultrasound-guided RFA offers the best combination of excellent visualization, real-time imaging guidance, and precise localization with minimal invasiveness. Several animal and human studies have demonstrated the technical feasibility and safety of endoscopic RFA in the pancreas. This article provides a comprehensive review of endoscopic RFA in the management of pancreatic lesions.     

Magnetocardiographically-Guided Catheter Ablation

After more than 30 years since the first magnetocardiographic (MCG) recording was carried out with induction coils, MCG is now approaching the threshold of clinical use. During the last 5 years, in fact, there has been a growing interest of clinicians in this new method which provides an unrivalled accuracy for noninvasive, three-dimensional localization of intracardiac source. An increasing number of laboratories are reporting data validating the use of MCG as an effective method for preoperative localization of arrhythmogenic substrates and for planning the best catheter ablation approach for different arrhythmogenic substrates. In this article, available data from literature have been reviewed. We consider the clinical use of MCG to localize arrhythmogenic substrates in patients with Wolff-Parkinson-White syndrome and in patients with ventricular tachycardia in order to assess the state-of-the-art of the method on a large number of patients. This article also addresses some suggestions for industrial development of more compact, medically oriented MCG equipments at reasonable cost.     

消融指数指导下射频消融术治疗心房颤动的效果研究

背景既往射频消融术治疗心房颤动主要根据术者的临床经验进行操作,而量化消融评价指标的出现可以缩短手术时间,提高手术成功率,减少并发症的发生。目的研究消融指数(AI)指导下射频消融术治疗心房颤动的有效性及安全性,以期为AI指导下射频消融术治疗心房颤动提供临床依据。方法选取2018年10月-2019年5月于中国人民解放军白求恩国际和平医院心血管内科行射频消融术的心房颤动患者69例为研究对象。采用随机数字表法将患者分为试验组(41例,在AI指导下行射频消融术)和对照组(28例,在接触压力参数指导下行射频消融术)。比较两组一般资料、手术相关指标〔包括手术总时间、X线透视时间、肺静脉隔离(PVI)单圈隔离情况、电复律使用情况、手术相关并发症发生情况〕、近期(术后3个月)复发情况,并记录试验组术中实际使用的AI。结果试验组手术总时间、X线透视时间短于对照组(P<0.05);两组PVI单圈隔离率、电复律使用率、手术相关并发症发生率比较,差异无统计学意义(P>0.05)。两组近期复发率比较,差异无统计学意义(P>0.05)。试验组术中实际使用的AI,左心房后壁多为370,功率为30 W;环肺底部多为370,功率为30 W;左心房前壁多为420,功率为35 W;左心房顶部多为390~420,功率为30 W;脊部多为420,功率为30 W。结论AI指导下射频消融术治疗心房颤动缩短了手术总时间和X线透视时间,且不增加PVI单圈隔离率、电复律使用率、手术相关并发症发生率、近期复发率,有益于术者安全、高效地完成手术。     

Real-Time Rotational ICE Imaging of the Relationship of the Ablation Catheter Tip and the Esophagus During Atrial Fibrillation Ablation

Introduction: Atrioesophageal fistula is a rare complication of atrial fibrillation (AF) ablation that should be avoided. We investigated whether rotational intracardiac echocardiography (ICE) can help to minimize ablation close to the esophagus.
Methods and Results: We studied 41 patients referred for catheter ablation of refractory AF. A rotational ICE catheter was inserted into the (LA) to determine the location of the esophagus. The esophagus was identified to be either adjacent to the pulmonary vein (PV) ostium or to a cuff 2 cm outside the ostium. Circumferential ablation was performed at the PV ostium, with the exact ablation location determined by ICE. The relationship of the catheter tip to the esophagus was imaged during energy delivery, allowing interruption when respiration moved the tip closer to the esophagus. Out of 41 patients, the esophagus was seen near left-sided PVs in 32 and near right-sided PVs in three patients. The median distance from LA endocardium to esophagus was 2.2 mm (range, 1.4–6 mm). In 21 of 35 patients with a closely related esophagus, ablation over the esophagus was avoided by ablating either lateral or medial to the esophagus. In 14 patients, the esophagus could not be avoided, and risk was minimized by limiting lesion size. Significant movement (>10 mm) of the esophagus during the procedure occurred in 3/41 cases.
Conclusion: Rotational ICE can accurately determine the distance of ablation sites from the esophagus. Real-time imaging of the relationship of the ablation catheter tip to the esophagus may reduce the incidence of esophageal injury.     

Electrogram-Guided Radiofrequency Catheter Ablation of Atrial Tissue Comparison with Thermometry-Guide Ablation

Objectives: To characterize a new method for radiofrequency energy titration during ablation of atrial tissue based on reduction in electrogram amplitude. To compare this method with energy titration using electrode thermometry. Background: Complications associated with anatomy-based atrial endocardial radiofrequency ablation for suppression of atrial fibrillation may be due to flawed methods of energy titration. Methods: The effect of radiofrequency ablation on electrogram amplitude was characterized in a porcine model. A method for energy titration guided by electrogram amplitude reduction (electrogram-guided) was developed and validated prospectively. Focal (smooth and trabeculated endocardial areas) and linear (smooth endocardial areas) ablation was performed comparing energy titration guided by amplitude reduction with electrode thermometry. Results: Amplitude reduction during radiofrequency application was not necessarily equal among unipolar and bipolar electrograms in the ablation region; specific patterns of reduction could be discerned, based on factors such as catheter-endocardial orientation. A criterion of >90% reduction of unipolar and/or bipolar amplitude best predicted pathologic lesion success. Electrogram-guided focal and linear lesions in smooth areas were free of lesion complications such as endocardial charring, barotrauma, or damage to contiguous extraatrial structures. However, there was a significant incidence of insufficient lesion size, principally non-transmurality, probably due to undertitration of energy. Thermometry-guided focal and linear lesions in smooth areas were uniformly transmural but frequently evidenced complications, due to overtitration of energy. Electrogram-guided focal lesions in trabeculated areas could usually not be achieved, probably due to insufficient contact of the ablation electrode with adjacent pectinate muscles. Thermometry-guided focal lesions in trabeculated areas were smaller than electrogram-guided lesions and did not evidence complications. Conclusions: Electrogram-guided lesions in smooth endocardial areas were uncomplicated but had a significant incidence of non-transmurality. Thermometry-guided lesions were uniformly transmural but were frequently complicated.     

Incidence of Pulmonary Vein Stenosis in Patients Submitted to Atrial Fibrillation Ablation: A Comparison of the Selective Segmental Ostial Ablation vs the Circumferential Pulmonary Veins Ablation

Introduction: Pulmonary vein (PV) stenosis is an important complication of the AF ablation and could be underestimated if their assessment is not systematically done. Selective Segmental Ostial Ablation (SSOA) and Circunferential Pulmonary Veins Ablation (CPVA) have demonstrated efficacy in atrial fibrillation (AF) treatment. In this study the real incidence of PV stenosis in patients (pts) submitted to both SSOA and CPVA was compared. Methods: Those pts with focal activity and normal left atrial size were submitted to SSOA, remaining pts were submitted to CPVA to treat refractory, symptomatic AF. Contrast enhanced magnetic resonance angiography (MRA) was routinely performed in all patients 4 months after the procedure. Results: A series of 73 consecutive patients (mean age of 51 ± 11 years; 75% male) were included. SSOA was performed in 32 patients, and the remaining 41 patients underwent to CPVA, obtaining similar efficacy rates (72% vs 76% arrythmia free probability at 12 months; log rank test p = NS). Six patients had a significant PV stenosis, all in SSOA group none in CPVA group (18.8% vs 0%; p = 0.005). All patients were asymptomatic and the stenosis was detected in routine MRA. No predictors of stenosis has been identified analysing patient procedure characteristics. Conclusion: PV stenosis is a potential complication of SSOA not seen in CPVA. The study confirms than MRA is useful for identifying patients with asymptomatic PV stenosis. Santiago Nava, A. Berruezo and A. Scalise were supported in part by a Grant from the Fundació Clínic per la Recerca Biomèdica.     

Initial Experience with a Novel Focused Ultrasound Ablation System for Ring Ablation Outside the Pulmonary Vein

Introduction: Atrial fibrillation has been shown to initiate from triggers within pulmonary veins. Several studies have documented that electrical isolation of those triggers can lead to maintenance of sinus rhythm. The complication of pulmonary vein stenosis has limited the utility of delivering ablation energy within the pulmonary vein. We utilize a focused ultrasound catheter ablation system for delivery of transmural ablation lines proximal to the pulmonary vein ostium. Methods: Nine dogs (weight 30–39 kg) were anesthetized and ventilated. Through a transseptal approach, pulmonary veins were engaged with the focused balloon ultrasound catheter. Ultrasound power was delivered at 40 acoustic watts outside the pulmonary vein ostium, focused 2 mm off the balloon surface, with a depth of approximately 6 mm, for 30–120 seconds. Following ablation, lesions were histopathologically analyzed. Results: Of nine animals studied, fourteen pulmonary veins were ablated. We found successful delivery of near circumferential and transmural ablation lines in 6/14 pulmonary veins. In each of the six circumferential ablations, successful alignment of the ultrasound transducer along the longitudinal axis of the parabolic balloon occurred. The final four ablations were conducted with an enhanced catheter design that assured axial alignment. Of these ablations, all four were circumferential. The remaining 8 pulmonary veins had incomplete delivery of lesions. In each of these veins the ultrasound transducer was misaligned with the balloon axis when therapy was delivered. Conclusion: Focused ultrasound ablation is a new means of performing pulmonary vein isolation. This method provides delivery of lesions outside the vein, limiting the risk of pulmonary vein stenosis for the treatment of atrial fibrillation.     

Ablation of the area postrema and emesis

The emetic action of dopmaine, norepinephrine, epinephrine, nicotine, dimethylphenyl-piperazinium (DMPP), and 4-m-chlorophenylcarbamoyloxy-2-butynyltrimefhylammonium (McN-A-343) injected intracerebroventricularly (i.c.v.) to the unanesthetized cat was investigated and compared. ED⁵⁰ values (mg) were as follows: nicotine, 0.011; epinephrine, 0.047; norepinephrine, 0.57; DMPP, 0.9; dopamine, 1.66; and McN-A-343, 4.42. The most potent was nicotine, whereas the least active McN-A-343. On the other hand, DMPP produced the longest emetic response, about 30 min, while McN-A-343-induced emesis lasted up to 1 min. The ablation of the area postrema abolished the emetic response to i.c.v. dopamine, norepinephrine, epinephrine, nicotine, and DMPP. However, the emetic response to i.c.v. McN-A-343 was significantly reduced in cats with an ablated area postrema. Taken together, the results obtained show that the area postrema is almost always involved in the central regulation of emesis and that the area postrema represents, in most cats, a common site of confluence of different inputs subserving the emesis.     

Biophysics of Ablation:

Introduction: The question of what happens to tissue during radiofrequency (RF) catheter ablation continues to be asked as we evolve into the use of newer delivery systems.
Methods and Results: Three assumptions are made about RF ablation. (1) Tissue injury is thermally mediated; (2) heat transfer in tissue should be a predictable biophysical phenomenon; and (3) large lesion technologies have more or less equivalent efficacies. Based on these assumptions, predictions are made and discussed. Many of the predictors were proven to be true while some surprisingly were not.
Conclusion: In conclusion, tissue-area injury occurs reproducibly at a temperature of about 50°C. Heat transfer in tissue is a predictable phenomenon. And finally, new technologies for large lesions are all effective, but greater surface area of ablation was achieved with a 10-mm tip and greater depth was achieved with a Chilli^® cooled ablation catheter.