Trans-myocardial bipolar electrogram: A strategy for mapping and determining efficacy of bipolar ablation of deep foci

Mapping and ablation of intramural ventricular tachycardia (VT) remain a challenge. We developed a trans-myocardial electrogram recording across distal tips of two separate ablation catheters placed on contralateral sides of the myocardium to record a trans-myocardial bipole and a novel pacing electrode configuration. This trans-myocardial bipole was applied during bipolar ablation in a patient with septal VT. Local activation in this trans-myocardial bipole was similar to the earliest activation recorded from detailed activation maps from both sides of the septum. Pacing from this trans-myocardial bipole resulted in a perfect morphology match. After bipolar ablation, the trans-myocardial bipolar voltage decreased by 82%, and pacing threshold increased by 800%. These findings correlated with VT noninducibility.     

Two-staged Biatrial Linear and Focal Ablation to Restore Sinus Rhythm in Patients with Refractory Chronic Atrial Fibrillation: Procedure Experience and Follow-up Beyond 1 Year

Recent observations regarding the mechanisms of chronic atrial fibrillation (CAF) plus a few encouraging clinical reports have created a paradigm shift regarding treatment strategies and the potential for restoring normal sinus rhythm (NSR) utilizing available catheter-based ablation techniques. The initial and late follow-up clinical experience with a two-staged biatrial linear and focal radiofrequency ablation (BALF I, II) procedure to restore NSR in patients with CAF are described. Pre-BALF management included confirming drug refractoriness and optimizing anticoagulation therapy. BALF I and II were preceded by trans-esophageal echocardiography to exclude thrombus. Femoral venous catheters were placed in the left atrium and the right atrium with extensive left atrial mapping, ablation (linear and focal) and more limited right atrial ablation. Localized electrogram recordings demonstrated rapid, localized, stable focal driving rotors (FDRs) in the left atrium (nine patients) and in the right atrium (one patient). Atrial or intraatrial tachycardia (IAT) commonly recurred after BALF I. BALF II addresses these recurrences by repeat mapping and ablation techniques. There were no thromboembolic complications. Two patients developed pericardial tamponade that responded to medical management. Of the 11 patients with late follow-up data, 9 have NSR, atrial function, and are no longer experiencing CAF. Left atrial ablation lines decrease continuous electrogram activity, probably isolate portions of the atrium, and unmask FDRs. Focal and linear ablations appear helpful in transforming CAF to NSR. FDRs are commonly localized to pulmonary vein ostium, trabeculated portions of the atrium, and left atrial appendage.     

肝血管瘤的诊治进展

肝血管瘤是肝脏肿瘤中的良性肿瘤,绝大多数肝血管瘤患者几乎不会出现临床症状或健康问题,患者往往是在因为其他健康问题检查时偶然发现肝血管瘤.肝血管瘤最常见的检查是超声或计算机断层扫描(CT).目前肝血管瘤的治疗方法较多,不同治疗方法的并发症及预后存在较大差异,因此本文对肝血管瘤的诊治展开综述.     

Radiofrequency Catheter Ablation Using Cooled Electrodes: Impact of Irrigation Flow Rate and Catheter Contact Pressure on Lesion Dimensions

WEISS, C., et al. : Radiofrequency Catheter Ablation Using Cooled Electrodes: Impact of Irrigation Flow Rate and Catheter Contact Pressure on Lesion Dimensions. Irrigation of radiofrequency current (RF) ablation reduces the risk of thrombus formation. The aim of this study was to investigate the impact of different irrigation catheter flow rates and contact pressures from the catheter on the development of lesion dimension and thrombus formation. A thigh muscle preparation was achieved in six sheep to create a cradle that was filled and perfused with heparinized blood (250 mL/min, 37C°). RF ablation (30 s, 30 W) was initially performed with three different irrigation flow rates (5 mL/min, 10mL/min, and 20 mL/min) and a perpendicular position (0.1 N contact pressure) of the irrigated ablation catheter (“Sprinklr,” Medtronic, Inc., Minneapolis, MN, USA). The next lesions were induced with constant contact pressure of 0.05 Newton (N); 0.1 N; 0.3 and 0.5 N and a parallel or perpendicular orientation of the catheter, respectively. A constant irrigation flow of 10 mL/min was maintained during these RF applications. Cross sections of the lesions were investigated with regard to maximal depth and maximal diameter at and below the surface. During high flow irrigation (20 mL/min) the surface diameter was significantly smaller (0.63 ± 0.1 cm ) compared to irrigation flow rates of 5 mL/min (0.88 ± 0.2 cm ) and 10 mL/min (1 ± 0.1 cm ). Thrombus formation was not observed during any RF application. Only in perpendicular catheter orientations with a contact pressure of 0.5 N were significantly deeper lesions (0.85 ± 0.12 cm ) induced compared to 0.05 N (0.55 ± 0.02 cm ), 0.1 N (0.7 ± 0.01 cm ) and 0.3 N (0.67 ± 0.01 cm ) contact pressure. There was no significant difference in lesion depth with different flow rates. Irrigated RF ablation even with low flow rates and high catheter contact pressure prevented thrombus formation at the electrode. Smaller lesion diameters have been created with high irrigation flow rates. The deeper lesion created with high catheter contact pressure might be caused by a greater power transmission to the tissue.     

Pulmonary vein isolation using a novel decapolar over-the-wire mapping and ablation catheter

Recently, a novel radiofrequency (RF) ablation system has been developed to perform pulmonary vein (PV) isolation. The system consists of a decapolar, steerable, over-the-wire mapping and ablation catheter combined with a multichannel RF generator that delivers energy in a temperature-controlled, power-limited fashion in both uni- and bi-polar modes. Using this technique, long continuous ablation lesions can be created within the left atrial antrum around the PV ostium. Electrical disconnection of PVs can be achieved in 93% of targeted PVs. Medium-term success is reported as 79.5% of patients with paroxysmal atrial fibrillation (no atrial fibrillation episodes detected during intensive holter monitoring). Ablation procedures using the novel technique are reported to be short (mean procedure duration: 84–201 min), including RF application duration of up to 40 min. Procedure-related complications are rare (1.8%) but the included total patient numbers are small and further studies on larger patient populations are needed.     

乙醇消融与射频消融治疗甲状腺囊实性结节疗效的评价分析

目的 研究乙醇消融和射频消融治疗甲状腺囊实性结节方面的疗效,并比较两种方法的治疗效果。方法 回顾性分析我院2014年2月至2015年6月在我院接受乙醇消融或射频消融的患有单个甲状腺囊实性结节的患者的住院资料,依据患者接受治疗方法的不同,将患者分为乙醇组(n=46)和射频组(n=49)。分析比较两组患者接受治疗后3个月、6个月、9个月及12个月甲状腺结节体积减少的情况;观察两种治疗方法在甲状腺结节不同囊实性比例情况下的治疗效果,同时分析不同体积情况下两种治疗方法的治疗效果。并对两组患者出现不良反应情况进行分析比较。结果 两组患者甲状腺结节均减小,但射频组患者结节体积缩小率（90.78±7.47）%明显高于乙醇组（69.71±4.95）%,差异具有统计学意义(P<0.05);随着甲状腺结节体积的增大,囊实性比例的缩小,两组患者甲状腺结节体积缩小率均减小。而当结节体积大于30ml时,结节囊实性比例不足50%,乙醇组体积缩小率不足50%,治疗无效。不论结节体积及囊实性比例的大小,射频组患者结节体积缩小率均显著高于乙醇组,结果具有统计学意义（P<0.05）;两组患者出现不良反应情况未见明显差异,结果无统计学意义(P>0.05)。结论 甲状腺囊实性结节小于30ml、囊实性比大于50%,乙醇消融经济且疗效确切,可做为首选;而结节体积较大,囊实性占位不足50%应用射频消融术治疗。     

Radiofrequency Ablation of Accessory Pathways: Characteristics of Transiently and Permanently Effective Pulses

The purpose of this study was to characterize and compare the radiofrequency current applications that produced permanent or transient accessory pathway conduction block. One hundred fifty-two radiofrequency energy applications that induced permanent (permanently effective pulses, n = 48) or transient (transiently effective pulses, n = 104) accessory pathway block in 57 patients with 60 accessory pathways were analyzed. The time from the onset of current application to disappearance of preexcitation or termination of supraventricular tachycardia by permanently effective pulses was 1-15 seconds (mean 3.6 +/- 3.8 sec) compared to 2-29 seconds (mean 11.5 +/- 7.5 sec) by transiently effective pulses (P less than 0.01). After transiently effective pulses that induced block in accessory pathway, conduction resumed within 5 minutes while induced block by permanently effective pulses persisted in 44 of 48 patients (92%) during follow-up of 11 +/- 12 months. The accessory pathway conduction returned in the remaining four patients after ablation 2 weeks to 7 months. After transiently effective pulses, 41 impulses were delivered to the same site using a higher power output (n = 32) and/or longer energy delivery duration (n = 20) without new mapping of accessory pathway location. Thirty-six of these impulses again resulted in transient accessory pathway block, four had no effect, only one impulse induced a permanent block in the accessory pathway. Pulses with higher power outputs tended to induce transient effects more frequently than pulses with lower energy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ablation of peri-"mitral" flutter in a patient with congenitally corrected transposition of great vessels and situs inversus

This case reports the successful ablation of a peri-"mitral" flutter in a patient with congenitally corrected transposition of the great vessels and situs inversus using an anterior mitral line.     

In Vitro and In Vivo Results of Transcatheter Microwave Ablation Using Forward-Firing Tip Antenna Design

This study was designed to test a microwave (MW) ablation system using approximately 2,450 MHz of energy and a deflectable catheter with forward-firing tip antenna, an early clinical prototype system. In vitro three-dimensional thermal mapping of single and double helix antenna designs was performed. Quantitative measurements of antenna radiation were recorded on tissue phantoms equipped with temperature sensors distributed radially and outwardly. In vivo testing consisted of closed-chest AV junction ablation in three dogs. Thermal mapping showed hemispherical heat distribution from the tip antenna. For the double helix design, this distribution was measured at 8,4-mm diameter with a maximum temperature of 61.62°C. As expected, the single helix design produced less heating with a measured diameter of 6.4 mm and maximum temperature of 55.90°C. The in vivo study produced lesions of geometry and size concordant with these heating patterns. MW ablation produced bundle branch block in one dog and complete AV nodal block in the remalning two, without transvalvular or other structural damage. The histopathology of the lesions was typical of a thermal burn showing hemorrhage and coagulative necrosis with clearly demarcated borders. We conclude that, using this early clinical prototype system with a deflectable catheter and a forward-firing tip antenna design, MW heating can produce a moderate-size lesion and is safe and effective for cardiac ablation.     

Left Atrial Linear Ablation to Modify the Substrate of Atrial Fibrillation Using a New Nonfluoroscopic Imaging System

Linear left atrial ablation is performed in combination with pulmonary vein (PV) isolation to improve the clinical results of atrial fibrillation (AF) ablation. These procedures require long procedures and fluoroscopic exposure. The aim of the present study was to evaluate the performance of a new, nonfluoroscopic, real-time, three-dimensional navigation system for linear ablation at the left atrial roof and mitral isthmus. The study included 44 patients (54 ± 10 years of age, 5 women) with drug-refractory AF, who underwent roof line or mitral isthmus linear ablation after 4-PV isolation. In 22 patients, ablation was performed with the navigation system (test group), and in the remainders linear ablation was performed with fluoroscopic guidance alone (control group). Conduction block was achieved in 20 patients (91%) in test group, and 21 patients (95%) in the control group (ns). Use of the navigation system was associated with a shorter fluoroscopic exposure for roof line (5.6 ± 3.0 minutes vs 8.7 ± 5.0 minutes, P < 0.05), and a trend for mitral isthmus ablation (7.8 ± 7.8 minutes vs 12.1 ± 5.9 minutes). It was also associated with a trend toward shorter procedure times for roof line (15.3 ± 8.6 minutes vs 22.9 ± 16.8 minutes) and mitral isthmus line (20.2 ± 15.8 minutes vs 32.0 ± 7.6 minutes) but no difference in duration of radiofrequency delivery. There was no procedural complication. The use of this new nonfluoroscopic imaging system was associated with a shorter fluoroscopic exposure as well as a trend toward shorter duration of linear ablation procedures for AF.     

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。     

Complications of radiofrequency ablation in hepatocellular carcinoma

Radiofrequency thermal ablation has been accepted as a promising technique to treat unresectable liver tumors. However, any interventional procedure should be performed only if the procedure is safe, with minimal morbidity and mortality rates. Recently, three separate multicenter surveys have reported acceptable morbidity and mortality rates for a minimally invasive technique. The mortality rate ranged from 0.1% to 0.5%, the major complication rate ranged from 2.2% to 3.1%, and the minor complication rate ranged from 5% to 8.9%. The most common causes of death were sepsis and hepatic failure, and the most common complications were intraperitoneal bleeding, hepatic abscess, bile duct injury, hepatic decompensation, and grounding pad burns. Minor complications and side effects are more common than major complications, but most of them are transient and self-limiting. Several strategies for avoiding or limiting the impact of complications after radiofrequency ablation are recommended: (a) careful patient selection, (b) combined treatment with other techniques when appropriate, (c) selection of the most appropriate guiding modality and approach, and (d) early detection and appropriate management of any major complications. Knowledge of the broad spectrum of complications and relevant management enables the operator to minimize the incidence and effect of any complications that occur after radiofrequency ablation.     

Microwave ablation of atrial flutter

Radiofrequency (RF) ablation of the isthmus between the inferior vena cava and the tricuspid ring has proven to be a safe and successful method of treating atrial flutter (AF). However, RF ablation lesions are small in size requiring a considerable number of energy applications to ablate the AF circuit. The aim of this study was to evaluate the feasibility and efficacy of microwave energy for AF ablation. We report a case of sustained typical AF treated successfully and safely by 1 pulse of microwave (MW) energy. This showed it is possible to treat AF with a small number of pulse applications.     

Mahaim纤维介导心动过速的标测和消融

[目的]探讨Mahaim's纤维参与折返的心动过速的电生理特点和射频消融结果.[方法]对5例患者,其中男4例,女性1例,年龄18～35(21.7±8)岁.在窦性心律或心房快速起搏情况下,消融导管沿三尖瓣环心房面标测,标测到有明显Mahaim's束电位处作为消融靶点.[结果]5例患者全部消融成功,旁路前传功能表现出递减传导特性,无逆传功能..靶点位置全部在三尖瓣环的心房侧8点或10点处,均能标测到明显的Mahaim's束电位.[结论]Mahaim's束电位的标测对治疗成功具有重要意义.     

Direct Current Shock Ablation: Quantitative Assessment of Proarrhythmic Effects

Catheter ablation using direct current (DC) shock has proved invaluable in the management of a variety of tachycardias. However, sporadic reports of fatal arrhythmias following ablation have raised the question of the proarrhythmic potential of DC shock ablation. The present study was undertaken in 45 patients to assess prospectively any proarrhythmia related to DC shock ablation, using matched pre- and postablation Holter monitors and programmed electrical stimulation (PES). Nineteen of these patients had Holter monitors for three successive postablation days to observe trends. There was unmatched data in 11 additional patients. All 56 patients provided prospective follow-up for clinical events. There was no immediate sustained VT/VF at the time of the ablation. Four patients had sustained VT in the first 72 hours after ablation; three episodes were similar to the preablation clinical arrhythmias; one patient had torsades de pointes interrupting bradycardia. Twelve patients met Holter, PES, or clinical criteria for proarrhythmia; none were treated on the basis of these findings. On Holter monitoring, there were significant increases in VPCs/hour and couplets/hour in patients undergoing atrial or atrioventricular junctional ablations; and an increase in couplets after accessory pathway ablations. Increases in these categories were not significant for VT patients; nor were increases in episodes of VT/hour or atrial arrhythmias significant in any group. Patients were followed for 44 +/- 33 months, with an actuarial survival of 95% at 1 year, 88% at 3 years, and 85% at 4 years. There were six deaths during follow-up. Two patients had sudden death: one at 2 months had early evidence of proarrhythmia; the other at 32 months may have represented later myocardia deterioration. One patient died of heart failure at 77 months; and there were three noncardiac deaths. DC shock ablation in humans is much less proarrhythmic than in dogs. The low incidence of clinical proarrhythmic events during prolonged follow-up after discharge resulted in low sensitivity, specificity, and positive predictive values for Holter and PES, although the negative predictive values of these tests were greater than 90%. Only one of 12 patients who met criteria for proarrhythmia in the days immediately following ablation had subsequent clinical events consistent with proarrhythmia. These results may be useful as standards for comparison with results of radiofrequency or other ablation modalities.