Management of Ventricular Tachycardia in Heart Failure

Ventricular tachyarrhythmias are common in patients with congestive heart failure. The clinical presentation ranges from an asymptomatic incidental electrocardiographic finding to palpitations, syncope, and sudden cardiac death. Although implantable cardioverter defibrillators successfully prevent sudden cardiac death associated with ventricular fibrillation and ventricular tachycardia, recurrent implantable cardioverter defibrillators shocks remain a clinical management challenge. In this review, we discuss management strategies of ventricular tachycardia in congestive heart failure, including drug therapy, radiofrequency catheter ablation (RFCA), and recent RFCA advances.     

射频消融术治疗室上性心动过速的现状与进展

评价射频消融术(RFCA)治疗室上性心动过速的现状与进展。综合国内外近10年RFCA治疗室上性心动过速的资料。RFCA是近年应用于临床与国际接轨较好的引进技术。RFCA是一种安全、有效的根治室上性心动过速的方法,成功率高,并发症低。正逐步用于治疗室上性心动过速、心房颤动等,发展前景广阔。     

Prise en charge d’une tachycardie ventriculaire récidivante sur cardiopathie non ischémique chez un patient implanté d’un défibrillateur

The benefit of implantable cardioverter defibrillators (ICD) on total mortality has been demonstrated in primary prevention for heart failure patients, in whom they improve clinical outcomes. However, some of these patients present incessant ventricular tachycardia and receive appropriated shocks and antitachycardia therapy. Radiofrequency catheter ablation is an efficacious method to prevent the occurrence of stable ventricular tachyarrythmias. We present here, the case of a patient with dilated cardiomyopathy implanted with an ICD in secondary prevention (ventricular tachycardia [VT]). The ICD delivered multiple appropriated shocks for monomorphic VT. A radiofrequency catheter ablation was successfully performed and the patient receives no further shock for the whole 18 months follow-up.     

Complications associated with radiofrequency catheter ablation of cardiac arrhythmias

Catheter ablation using radiofrequency energy has evolved as a safe and effective means for the treatment of various supraventricular and ventricular arrhythmias. Despite the overall efficacy of radiofrequency catheter ablation, cardiovascular complications can occur in a small number of patients. The purpose of this article is to review the current understanding of the risks and complications that can occur during catheter ablation procedures.     

快慢型房室结折返性心动过速的电生理机制和经导管射频消融

目的探讨快慢型房室结折返性心动过速(AVNRT)的电生理机制和经导管射频消融。方法快慢型AVNRT消融患者42例。消融方法为在心室起搏或心动过速时标测最早逆传慢径心房激动部位,然后在窦性心律下或心动过速时消融。消融成功的标准为消除逆传慢径、1:1前传慢径及不能诱发任何类型AVNRT。结果所有42例均消融成功。逆传慢径消融成功部位在三尖瓣环和冠状静脉窦(CS)口之间(传统慢径区域)36例(86%),其最早逆传心房激动也位于上述区域;逆传慢径在CS近端或/和二尖瓣环心房侧消融成功6例(14%),其最早逆传心房激动多位于CS近端1～3cm处。结论多数快慢型AVNRT可在传统慢径区域(房室结右侧后延伸)消融成功,但部分病例需要在CS近端和/或二尖瓣环房侧(左侧后延伸)消融成功。     

Treatment of supraventricular tachycardias with transcatheter delivery of radiofrequency current.

Medical therapy for the treatment of supraventricular tachycardias is frequently ineffective and associated with significant side effects, whereas curative surgical approaches have generally been limited by their considerable morbidity and cost. Greater understanding of the mechanisms underlying supraventricular tachycardias has improved our ability to precisely map endocardial areas critical to arrhythmogenesis. Advances in catheter ablation techniques and particularly the use of radiofrequency current to generate thermal energy for ablation have resulted in dramatic success rates for curative catheter ablation. This review examines the physics of radiofrequency current ablation and its application to the treatment of atrial fibrillation, atrial flutter, AV nodal reentrant tachycardia, and arrhythmias associated with the Wolff-Parkinson-White syndrome. The limitations, risks, and cost-effectiveness of this technique relative to medical and surgical approaches are also evaluated.     

Catheter ablation of ventricular tachycardia using radiofrequency current.

Catheter ablation techniques have evolved as an alternative to map-guided surgery and proven effective in a variety of supraventricular tachyarrhythmias. Direct current catheter ablation has been shown to be effective in about 50 to 70% of cases. Approximately, 60% of patients with structural heart disease and monomorphic ventricular tachycardia were successfully treated using direct current ablation techniques. This overall success rate and possible risks associated with the use of direct current have stimulated the search for other energy sources appropriate for catheter ablation. Presently, only a few preliminary reports on the clinical efficacy of radiofrequency energy for the treatment of ventricular tachyarrhythmias in man exist. 23 patients with identifiable heart disease at a mean age of 52 +/- 17 years underwent radiofrequency catheter ablation. 16 patients had coronary artery disease, one patient dilative cardiomyopathy and six patients had arrhythmogenic right ventricular disease. All patients presented with chronic current sustained ventricular tachycardia. After detailed endocardial catheter mapping radiofrequency energy was applied at the site of earliest ventricular activation during ventricular tachycardia which could be entrained during fixed rate ventricular pacing at the site of origin of ventricular tachycardia. At all ablation sites a long latency between the stimulus and QRS complex was noted. Of 23 patients 18 were treated with radiofrequency alone whereas in five patients a second ablation procedure using direct current was performed. Following the ablation procedures, 14 patients (61%) remained free of ventricular tachycardia. One patient died due to congestive heart failure 21 months following ablation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Safety of Remote Magnetic Navigation in Patients With Pacemakers and Implanted Cardioverter Defibrillators

Magnetic Navigation and Implanted Devices. Background: Remote magnetic catheter navigation (MNS) has been shown to be feasible and safe for radiofrequency catheter ablation of various cardiac arrhythmias. However, its safety in patients with implanted pacemakers or cardioverter–defibrillators has not yet been studied. Objectives: This retrospective case series study intends to assess the acute and short‐term safety of remote MNS in patients with implanted pacemakers or cardioverter–defibrillators. Methods: Between January 2008 and June 2009, a total of 31 patients with implanted pacemakers (n = 5) or cardioverter–defibrillators (n = 26) underwent 32 catheter ablation procedures using the remote MNS. Baseline pacing thresholds, sensed amplitudes, pacing and, if available, shock impedances as well as battery status were measured in all devices before, immediately after, and 1–3 months after catheter ablation. Results: After ablation, no statistically significant difference in atrial sensing (2.7 ± 1.5 mV vs 3.1 ± 1.9 mV, P = 0.18) and impedance (457 ± 104 Ω vs 449 ± 101 Ω, P = 0.37) were observed. After ablation, no statistically significant difference in right ventricular sensing (10.4 ± 3.8 mV vs 10.9 ± 4.9 mV, P = 0.43) and impedance (535 ± 118 Ω vs 534 ± 120 Ω, P = 0.913) were observed. No changes in pacing threshold could be observed in all but 2 patients with biventricular cardioverter–defibrillators who underwent ventricular tachycardia ablation in lateral wall of left ventricle near the implanted epicardial electrode. Conclusions: Ablation procedures using remote MNS can be performed safely in patients with implanted devices with no significant effects on device system integrity. Long endocardial ablation close to the insertion site of the implanted epicardial left ventricular leads can affect the pacing and/or sensing characteristics of these electrodes. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1130‐1135)     

Catheter ablation of the atrioventricular junction using radiofrequency energy and a bilateral cardiac approach.

Radiofrequency current catheter ablation was used successfully to create complete atrioventricular (AV) block in 60 of 61 patients (98%) with drug refractory supraventricular tachyarrhythmias. The remaining patient developed Mobitz I AV block and is clinically improved (clinical efficacy 100%). In 54 patients (89%), complete AV block was achieved using a right-sided approach. Patients aged > 60 years needed significantly fewer right-sided radiofrequency applications to produce complete AV block (5.3 +/- 5.3 vs 11.1 +/- 10.0; p = 0.009). In 6 of 7 patients with unsuccessful right-sided ablation, a left ventricular approach was used. In each case, 1 to 4 additional radiofrequency applications produced complete AV block. Patients with unsuccessful right-sided ablation were generally younger than those with successful ablation (50 +/- 16 vs 64 +/- 11; p = 0.007). It is concluded that catheter ablation using radiofrequency current is an extremely effective means of producing complete AV block. Older patients appear to be more susceptible to right-sided radiofrequency approaches. Left ventricular ablation easily produces complete AV block in patients refractory to right-sided attempts.     

Closed chest catheter desiccation of the atrioventricular junction using radiofrequency energy--a new method of catheter ablation

Closed chest catheter ablation of the atrioventricular (AV) junction has been performed with direct current or laser energy. The effect of 750 kHz radiofrequency energy on ablation of the AV junction was evaluated in 13 dogs. The radiofrequency energy was generated from an electrosurgical generator in the bipolar mode. The radiofrequency output was delivered between two distal electrodes (bipolar ablation) in eight dogs, and between the distal electrode and an external patch electrode (unipolar ablation) in another five dogs at varying power (watts) but with a constant pulse duration of 10 seconds. Complete AV block was achieved in 11 dogs and second degree AV block in 2. During the 4 to 7 day follow-up period, complete AV block persisted in 9 of the 11 dogs with initial complete heart block. The other two had return of AV conduction; one had persistent 2:1 AV block and the other had persistent first degree AV block. Of the two dogs with initial second degree AV block, one developed complete AV block, the other had resumption of 1:1 AV conduction with a normal PR interval. Energy was delivered in 1 to 13 applications per dog. One hundred to 700 J per application was delivered with bipolar ablation and 10 to 100 J with unipolar ablation. There was no damage to the catheter unless the catheter was repeatedly used in excess of 1,500 J of total energy. Ventricular arrhythmias were not observed. Pathologic examination showed well delineated coagulation necrosis at the AV junction without surrounding hemorrhage or mural thrombus. Microscopic findings consisted of necrosis with cell infiltration in the periphery of necrosis. Most injuries involved the AV node, the approaches to the AV node and the penetrating bundle. In conclusion, catheter ablation of the AV junction with radiofrequency energy is safe. It can effectively induce discrete areas of necrosis and produce various degrees of AV block. In addition, ablation by radiofrequency energy has distinct advantages as compared with catheter ablation with direct current or laser energy.     

Neonatal Radiofrequency Catheter Ablation of Junctional Tachycardias

Junctional tachycardias comprise several arrhythmia types with differing mechanisms, principally involving the region of the atrioventricular (A-V) junction. Neonatal radiofrequency catheter ablation has typically been reserved for life-threatening, drug-refractory cases due to the unique concerns regarding patient size and development. We performed radiofrequency catheter ablation on two neonates with incessant, rapid junctional tachycardias and hemodynamic compromise after failing conventional medical therapy. This report describes 2 neonates who underwent emergent radiofrequency catheter ablation, and compares these two patients to a larger pediatric catheter ablation patient cohort. Both neonates had an acutely successful outcome and were able to be discharged within a week of the ablation procedure. Fluoroscopy time and total procedure time were shorter in these two patients than in the course of the average pediatric catheter ablation. Though long-term developmental consequences of neonatal catheter ablation are yet unknown, in unique extreme situations, radiofrequency catheter ablation can be performed in neonates, as in older children and adults, without excessive acute morbidity.     

Curative percutaneous catheter ablation using radiofrequency energy for accessory pathways in all locations: results in 100 consecutive patients.

Patients with accessory pathway-mediated supraventricular tachycardia have typically been treated with drugs or surgery. Although catheter ablation using high voltage direct current shocks has been used to treat patients with drug-refractory supraventricular tachycardia, there are associated disadvantages, including damage due to barotrauma as well as the need for general anesthesia. Recently, transcatheter radiofrequency energy has evolved as an alternative to direct current shock or surgery to ablate accessory pathways. Percutaneous catheter ablation of 109 accessory pathways with use of radiofrequency energy was attempted in 100 consecutive patients. Patient age ranged from 3 to 67 years. The patients had been treated for recurrent tachycardia with a mean of 2.7 +/- 0.2 antiarrhythmic agents that either proved ineffective or caused unacceptable side effects. In seven patients previous attempts at accessory pathway ablation with use of direct current shock had been unsuccessful. Forty-five (41%) of the pathways were left free wall, 43 (40%) were septal and 21 (19%) were right free wall. Eighty-nine (89%) of the 100 patients had successful radiofrequency ablation at the time of hospital discharge. In all but 12 patients the ablation was accomplished in a single session. Complications attributable to the procedure, but not to the ablation itself, occurred in four patients (4%). No patient developed atrioventricular block or other cardiac arrhythmias. Over a mean follow-up period of 10 months, nine patients had some return of accessory pathway conduction; a repeat ablation procedure was successful in all five patients in whom it was attempted. It is concluded that a catheter ablation procedure using radiofrequency energy can be performed on accessory pathways in all locations. The procedure is effective and safer, less costly and more convenient than cardiac surgery and can be considered as an alternative to lifelong medical therapy in any patient with symptomatic accessory pathway-mediated tachycardia.     

Catheter ablation of accessory atrioventricular pathways in 114 symptomatic patients with Wolff-Parkinson-White syndrome--a comparative study of direct-current and radiofrequency ablation.

To evaluate and compare the safety and efficacy of catheter-mediated direct-current and radiofrequency ablation in patients with Wolff-Parkinson-White syndrome, 114 patients with accessory pathway-mediated tachyarrhythmias underwent catheter ablation. Electrophysiologic parameters were similar in patients undergoing direct-current (group 1, 52 patients with 53 accessory pathways) and radiofrequency (group 2, 62 patients with 75 accessory pathways) ablation. Immediately after ablation, 50 of 53 accessory pathways (94%) were ablated successfully with direct current, but 2 of the 50 accessory pathways had early return of conduction and required a second ablation; 72 of 75 accessory pathways (96%) were ablated successfully with radiofrequency current. In the three accessory pathways in which radiofrequency ablation was unsuccessful, a later direct-current ablation was successful. During follow-up (group 1, 14 to 27 months; group 2, 8 to 13 months), none of the patients with successful ablation had a recurrence of tachycardia. Complications in direct-current ablation included transient hypotension (two patients), accidental atrioventricular block (one patient), and pulmonary air trapping (two patients); complications in radiofrequency ablation included cardiac tamponade (one patient) and suspicious aortic dissection (one patient). Myocardial injury and proarrhythmic effects were more severe in direct-current ablation. The length of the procedure and the radiation exposure time were significantly shorter in direct-current (3.5 +/- 0.2 hours, 30 +/- 4 minutes) than in radiofrequency (4.1 +/- 0.4 hours, 46 +/- 9 minutes) ablation. Findings in this study confirm the impression that radiofrequency ablation is associated with fewer complications than direct-current ablation and radiofrequency ablation with a large-tipped electrode catheter is an effective and relatively safe nonsurgical method for treatment of Wolff-Parkinson-White syndrome.     

Ablation of the atrioventricular junction with radiofrequency energy using a new electrode catheter

Percutaneous catheter ablation using radiofrequency energy can be used to interrupt atrioventricular (AV) conduction in patients with supraventricular tachycardia refractory to drugs. Results of radiofrequency ablation of the AV junction using a custom-designed catheter with a large, 3-mm-long distal electrode, 2-mm interelectrode spacing, and a shaft with increased torsional rigidity were compared with those using a standard quadripolar electrode catheter (Bard EP). An electrocoagulator (Microvasive Bicap 4005) supplied unmodulated radiofrequency current at 550 kHz, which was applied between the distal electrode of the ablation catheter and a large skin electrode. With use of the modified catheter, 12 of 13 patients (92%) had persistent complete AV block induced with 7 +/- 5 applications of 18 +/- 6 W of radiofrequency power. In contrast, complete AV block was produced in only 9 of 18 (50%) historical control patients treated with the standard catheter, despite a similar number of applications (7 +/- 5) and power output (16 +/- 4 W). A rise in impedance, due to desiccation of tissue and coagulum formation, occurred earlier (28 +/- 18 vs 52 +/- 24 seconds, p less than 0.001) and more frequently (54 vs 40% of applications, p = 0.047) in patients treated with the standard catheter than in patients treated with the modified catheter. The use of a catheter designed to increase the surface area of electrode-tissue contact allows more radiofrequency energy to be delivered before a rise in impedance occurs and appears to increase the effectiveness of radiofrequency ablation of the AV junction.     

通过动物实验评价射频能量对冠状动脉的急性损伤

目的通过动物实验观察射频消融术(RFCA)是否会导致冠状动脉(简称冠脉)的急性损伤,对比不同的消融方法对冠脉的影响。方法取成年犬21只,雌雄不限,随机分三组,第一组消融电极为4mm,能量级别设定为60℃/120s,分别消融左房室环、右房室环、冠状静脉窦内和心外膜的近冠脉处;第二组能量级别设定为80℃/120s,分别消融除心外膜外的其它三处;第三组消融电极为8mm,能量级别设定为60℃/120s,仅消融左右房室环。术毕观察消融点附近冠脉损伤情况,并取消融点及附近冠脉作病理检查,光镜下观察心肌和冠脉的变化。结果大体下观察,没有发现冠脉管腔的狭窄及管腔内血栓形成。对63处消融点附近的冠脉进行光镜检查时,3例冠脉或其分支出现明显变化,动脉壁破裂、壁结构消失、平滑肌溃疡、变性坏死,溃疡内有大量白细胞浸润;9例冠脉内皮细胞出现肿胀、脱落甚至消失;其余冠脉未有任何变化。结论常规RFCA是安全可靠的,但特殊部位、高能量射频消融时,应注意冠脉的损伤。     

Catheter ablation of septal accessory conduction pathways with high frequency electric current]

In 58 symptomatic patients with septal accessory atrioventricular pathways, attempts at catheter ablation of the pathway were made using 500-kHz radiofrequency current. The methodological approach (introduction and final positioning of the ablation catheter) was dependent on the anatomical site of the accessory pathway. Right anteroseptal pathways were accessed via a jugular venous route, whereas a femoral venous route was used for right mid- and posteroseptal pathways. In these pathways, ablation was attempted from an atrial catheter position. Left posteroseptal pathways were located via mapping of the coronary sinus and were ablated either from the left ventricle or (in 3 cases) from the vena cordis media. Utilizing a deflectable catheter with a 4-mm tip electrode, ablation attempts were successful in 54 patients (93%) with a median of 12 radiofrequency current pulses of an average 24.9 W of power and 23.2 s length. The mean duration of the sessions was 4.6 h. Impairment of physiological conduction (first-degree AV block) was observed in 1 patient; complete heart block was never induced. Recurrences after initially successful ablation necessitated a repeat session in 2 patients. One patient died 3 days after successful ablation of a posteroseptal accessory pathway. Septal accessory pathways may be ablated using radiofrequency current with an efficacy and safety comparable to free-wall accessory pathways and with good preservation of physiological AV node-His bundle conduction.     

经导管射频消融心律转复除颤器植入后电风暴

目的报道3例心律转复除颤器（ICD）植入后抗心律失常药物治疗无效的室性心律失常电风暴患者经导管射频消融的结果。方法2名男性与1名女性患者,年龄为75、55、37岁,分别患有陈旧性前壁心肌梗死、致心律失常性右心室心肌病、左心室心肌病。均在ICD植入后发生抗心律失常药物治疗无效的电风暴。应用Carto电解剖标测系统引导盐水灌注射频导管标测和消融室性心动过速（VT）。对可标测VT（持续性、血流动力学稳定）行激动和拖带标测;对不可标测VT,则在基质标测的基础上行起搏标测和／或短时间的拖带标测。结果3例患者中共诱发出5种形态的VT,4种血流动力学较稳定VT和1种血流动力学不稳定VT。成功消融了所有形态的VT,抑制了电风暴的急性发作。消融后随访的6、19和36个月中,仅1例患者出现1次ICD放电。结论在电解剖标测的基础上,应用盐水灌注射频导管消融ICD植入后抗心律失常药物治疗无效的电风暴有很好的疗效。     

射频导管消融中温度场模型的建立

通过了解射频导管消融心肌形成损伤斑的过程，探讨一些主要因素（功率、消融时间、血流等）与形成损伤斑的关系以及对损伤深度的影响，提出了建立在射频电流组织加热和热传导基础上的射频导管消融中温度场的一维理论模型，初步分析了血流对温度场分布的影响，得出：稳定后的温度场在径向的分布基本上与距离的四次方及血流速度成反比；近场温度场建立过程的时间常数与血流速度成反比，与径向距离的平方成反比，即离导管端电极越近，温度升高得越快，达到稳定的时间越短。仿真计算的结果提示要加深有效消融的深度而又不致在导管端电极头引起凝血与炭化，可以考虑加大电极头的面积或用电极矩阵来进行射频消融的加热，同时也可以考虑“冷却导管端电极”（如将低温生理盐水引入导管内，再从电极头部喷出）的方式。     

Comparison of late results of surgical or radiofrequency catheter modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia.

AIMS: Although arrhythmia surgery and radiofrequency catheter ablation to cure atrioventricular nodal reentrant tachycardia differ in technical concept, the late results of both methods, in terms of elimination of the arrhythmogenic substrate and procedure-related new and different arrhythmias, have never been compared. This constituted the purpose of this prospective follow-up study. METHODS AND RESULTS: Between 1988 and 1992, 26 patients were surgically treated using perinodal dissection or 'skeletonization', and from 1991 up to 1995, 120 patients underwent radiofrequency modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia. The acute success rates of surgery and radiofrequency catheter ablation were 96% and 92%, respectively. Late recurrence, rate in the surgical and radiofrequency catheter ablation groups was 12% and 17%, respectively. Mean follow-up was 53 months in the surgical group and 28 months in the radiofrequency catheter ablation group. The final success rate after repeat intervention was 100% in the surgical group and 98% in the radiofrequency catheter ablation group. Comparison of the initial and recent series of radiofrequency catheter ablated patients showed an increased initial success rate with fewer applications. In the radiofrequency catheter ablation group, a second- or third-degree block developed in three patients (2%), requiring permanent pacing, whereas in the surgical group no complete atrioventricular block was observed. Inappropriate sinus tachycardia needing drug treatment was observed in 13 patients (11%), mostly after fast pathway ablation, but was never observed after surgery. New and different supraventricular tachyarrhythmias arose in 27% of the patients in the surgical group and in 11% of the radiofrequency catheter ablation group, but did not clearly differ. CONCLUSION: This one-institutional follow-up study demonstrated comparable initial and late success rates as well as incidence of new and different supraventricular arrhythmias following arrhythmia surgery and radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia. Today radiofrequency catheter ablation has replaced arrhythmia surgery for various reasons, but the late arrhythmic side-effects warrant refinement of technique.     

Radiofrequency catheter ablation of right ventricular outflow tachycardia in children and adolescents

Objectives. The current study reviews the safety and efficacy of radiofrequency catheter ablation for the treatment of right ventricular outflow tachycardia in children and adolescents and describes a modified method for mapping the tachycardia focus.Background. Although radiofrequency catheter ablation has proved highly effective for the treatment of supraventricular tachycardia during childhood and adolescence, its application in children with idiopathic right ventricular outflow tachycardia has been limited.Methods. Six children (mean [±SD] age 10.6 ± 2.4 years, range 6 to 16) with right ventricular outflow tachycardia underwent seven radiofrequency catheter ablation procedures. The mean tachycardia cycle length was 323 ± 24 ms (range 300 to 360). Two multipolar catheters were positioned in the right ventricular outflow tract to map the tachycardia focus.Results. Radiofrequency catheter ablation was successful in five (83%) of the six children (95% confidence interval 36% to 99%). At successful ablation sites, local endocardial activation times preceded the surface QRS onset by 46 ± 5 ms (range 37 to 57), and there was concordance of the 12-lead pace map and the electrocardiogram (ECG) in 11 (one patient) to 12 ECG leads (four patients). One patient developed complete right bandle branch block during radiofrequency catheter ablation. There were no additional complications and no clinical recurrences over a mean follow-up period of 12.7 ± 3.8 months (range 9 to 22).Conclusions. These results suggest that radiofrequency catheter ablation is a safe effective treatment for right ventricular outflow tachycardia during childhood and adolescence. In addition, tachycardia mapping may be enhanced by use of a multipolar right ventricular outflow catheter technique.