Usefulness of epicardial impedance evaluation for epicardial mapping and determination of epicardial ablation site for ventricular tachycardia: A pilot study

1 Background

During epicardial mapping, determination of appropriate ablation sites in low voltage areas (LVA) is challenging because of large epicardial areas covered by adipose tissue.

2 Objective

To evaluate the impedance difference between epicardial fat and the epicardial LVA using multiple detector computed tomography (MDCT).

3 Methods

We enrolled patients who underwent ventricular tachycardia (VT) ablation via the epicardial approach after endocardial ablation failure. After the procedure, MDCT‐derived images of epicardial fat were loaded to the mapping system. Then, all points acquired during sinus rhythm were retrospectively superimposed and analyzed.

4 Results

This study included data from 7 patients (62.5 ± 3.9 years old) who underwent eight epicardial VT ablation procedures. After the procedure, MDCT‐derived images of epicardial fat were registered in eight procedures. Retrospective analysis of 1,595 mapping and 236 ablation points was performed. Of the 1,595 mapping points on the merged electroanatomical and epicardial fat maps, normal voltage area (NVA) and low voltage area (LVA) without fat had lower impedance than those with fat (NVA without fat 182 ± 46 Ω vs. NVA with fat 321 ± 164.0 Ω, P  =  0.001, LVA without fat 164 ± 69 Ω vs. LVA with fat 248 ± 89 Ω, P  =  0.002). Of the 236 ablation points, initial impedance before ablation was higher on epicardial fat than on epicardial LVA without fat (134 ± 16 Ω vs. 156 ± 28 Ω, P  =  0.01).

5 Conclusions

Real time epicardial impedance evaluation may be useful to determine effective epicardial ablation sites and avoid adipose tissue. However, the number of patients in the present study is limited. Further investigation with a large number of patients is needed to confirm our result.     

Ventricular tachycardia in ischemic heart disease substrates

Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic cardiac injury. Post-infarct structural and functional remodeling results in electrophysiologic substrates at risk for monomorphic ventricular tachycardia (MMVT). Characterization of this substrate using a variety of clinical and investigative tools has improved our understanding of MMVT circuits, and has accelerated the development of device and catheter-based therapies aimed at identification and elimination of this arrhythmia.This review will discuss the central role of the ischemic heart disease substrate in the development MMVT. Electrophysiologic characterization of the post-infarct myocardium using bipolar electrogram amplitudes to delineate scar border zones will be reviewed. Functional electrogram determinants of reentrant circuits such as isolated late potentials will be discussed. Strategies for catheter ablation of reentrant ventricular tachycardia, including structural and functional targets will also be examined, as will the role of the epicardial mapping and ablation in the management of recurrent MMVT.     

Epicardial mapping and radiofrequency catheter ablation of ischemic ventricular tachycardia using a three-dimensional nonfluoroscopic mapping system

Endocardial radiofrequency catheter ablation of ischemic left ventricular tachycardia has been of variable success due to multiple factors. Two such factors include the location of the reentrant circuit in the deep myocardium or on the epicardial surface and the inherent limitations of fluoroscopy as a guide for target localization. We report a patient in whom successful epicardial mapping and radiofrequency catheter ablation of an ischemic left ventricular tachycardia was performed using pericardial access and the CARTO electroanatomic mapping system.     

Identification of an epicardial slow conduction channel using ripple mapping in ablation of postinfarct ventricular tachycardia

An 82‐year‐old man underwent redo catheter ablation of ventricular tachycardia (VT) after anterior infarction. A ripple mapping conducting channel (RMCC) was identified within the anterior scar in the left ventricular epicardium during sinus rhythm. Along the RMCC, delayed potentials during sinus rhythm, a good pace map with a long stimulus to the QRS interval, and mid‐diastolic potentials during VT were recorded, and epicardial ablation at this site eliminated the VT. These findings suggested that the RMCC in the epicardial scar served as a critical isthmus of the postinfarct VT, and ablation targeting the RMCC was effective.     

Right ventricular scar‐related ventricular tachycardia in nonischemic cardiomyopathy: Electrophysiological characteristics,mapping, and ablation of underlying heart disease

1 Background

Right ventricular (RV)‐scar related ventricular tachycardia (VT) is often due to arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) or cardiac sarcoidosis (CS), but some patients whose clinical course has not been described do not fulfill diagnostic criteria for these diseases. We sought to characterize the electrophysiologic substrate and catheter ablation outcomes of such patients, termed RV cardiomyopathy of unknown source (RCUS).

2 Methods and results

Data of 100 consecutive patients who presented with RV cardiomyopathy and/or RV‐related VT for ablation were reviewed (51 ARVC/D, 22 CS; 27 RCUS). Compared to ARVC/D, RCUS patients were older (P = 0.001), less commonly had RV dilatation (P = 0.001) or dysfunction (P = 0.01) and fragmented QRS, parietal block, and T‐wave inversion. Compared to CS, R‐CUS patients had less severe LV dysfunction. Extent and distribution of endocardial/epicardial scar and inducible VTs in RCUS patients were comparable with ARVC/D and CS patients. At a median follow‐up of 23 months, RCUS patients had more favorable VT‐free survival (RCUS 71%, ARVC/D 60%, CS 41%, P = 0.03) and survival free of death or cardiac transplant (RCUS 92%, ARVC/D 92%, CS 62%, P = 0.01). No RCUS patients developed new criteria for ARVC/D or CS in follow‐up.

3 Conclusions

Up to one‐third of patients with RV scar‐related VT are not classifiable as ARVC/D or CS. These patients had a somewhat better prognosis than ARVC/D or sarcoid and did not develop evidence of these diseases during the initial 2 years of follow‐up. The extent to which this population comprises mild ARVC/D, CS, or other diseases is not clear.     

Repeat percutaneous epicardial mapping and ablation of ventricular tachycardia: safety and outcome

Safety and Efficacy of Repeat Epicardial Access. Introduction: Epicardial mapping and ablation of ventricular tachycardia (VT) has been increasingly performed. Occasionally additional ablation is necessary, requiring repeat percutaneous access to the pericardial space. Methods and Results: We studied 30 consecutive patients who required a repeat epicardial procedure. We specifically examined the success and safety of repeat percutaneous pericardial access as well as the ability to map and ablate epicardial VT targets. Percutaneous pericardial access at a median of 110 days after the last procedure was successful in all 30 patients. Significant adhesions interfering with catheter mapping were encountered in 7 patients (23%); 6 had received intrapericardial triamcinolone acetate (IPTA) with prior procedures. Using blunt dissection with a deflected ablation catheter and a steerable sheath, adhesions were divided allowing for complete catheter mapping in 5 patients with areas of dense adherence compartmentalizing the pericardium in 1 patient and precluding ablation over previously targeted ablation site in the second. Targeted VT noninducibility was achieved in 27 (90%) patients including 7 patients with adhesions. No direct complications related to pericardial access or adhesions disruption occurred. One periprocedural death occurred from refractory cardiogenic shock in patient with LV ejection fraction of 10%. Another patient developed asymptomatic positive Haemophilus influenzae pericardial fluid cultures identified at second procedure, which was successfully treated. Conclusions: Repeat access can be obtained after prior epicardial ablation. Adhesions from prior procedures may limit mapping, but can usually be disrupted mechanically and allow for ablation of recurrent VT. IPTA may not completely prevent adhesions. (J Cardiovasc Electrophysiol, Vol. 23, pp. 744‐749, July 2012)     

Substrate-based catheter ablation of epicardial ventricular tachycardia related to an anomalous coronary artery

Delayed enhancement magnetic resonance imaging is known for its ability to identify scarred myocardial tissue. This case report describes the use of MR imaging to define the location and transmural extent of infarcted tissue in a 45-year-old woman with an anomalous right coronary artery and hemodynamically unstable ventricular tachycardia. By demonstrating a predominantly epicardial infarct, MR imaging indicated that the pericardial approach was necessary for successful substrate-based ventricular tachycardia ablation.     

心外膜室性心动过速的心电图特征

心外膜室速的心电图有其共同表现：QRS 时限≥200 ms,但也有部分时限≤120 ms;起始部有假性Δ波≥34 ms;电轴多数左偏,胸前导联移行在 V2以后;V2导联 R 波达峰值时间延长≥85 ms;最短 RS 时间≥121 ms。识别左心室起源的心外膜室速：Ⅰ导联呈 Q 波的基底、心尖部室速;Ⅱ、Ⅲ、aVF 导联无 Q 波的基底部室速;Ⅱ、Ⅲ、aVF 导联呈 Q 波的基底上部、心尖部室速;最大转折指数可识别左室流出道心外膜室速,当最大转折指数≥0．55可识别远离主动脉窦的心外膜室速。识别右心室起源的心外膜室速：Ⅰ导联呈 Q 波且右室前壁导联呈 QS,预示心外膜室速可能性大;Ⅱ、Ⅲ、aVF 导联起始 Q 波,可在同步电生理标测时观察到位于右心室心外膜起源的室速。但不同部位及不同病因的室速又有其特殊性,术前通过体表心电图进行较为精确的定位对室速消融有一定的指导意义。     

Mapping and radiofrequency catheter ablation of the three types of sustained monomorphic ventricular tachycardia in nonischemic heart disease

INTRODUCTION: Sustained monomorphic ventricular tachycardia (VT) associated with nonischemic cardiomyopathy (CMP) is uncommon. Optimal approaches to catheter mapping and ablation are not well characterized, but they are likely to depend on the VT mechanism. The purpose of this study was to evaluate the mechanisms of sustained monomorphic VT encountered in nonischemic CMP and to assess the feasibility, safety, and efficacy of catheter radiofrequency ablation for treatment. METHODS AND RESULTS: Twenty-six consecutive patients with nonischemic CMP referred for management of recurrent VT were studied. In 16 (62%) patients, VT was related to a region of abnormal electrograms consistent with scar and the response to pacing suggested a reentrant mechanism. In 5 (19%) patients, VT was due to bundle branch or interfascicular reentry. In 7 (27%) patients, the VT mechanism was focal automaticity, 4 of whom had evidence of tachycardia-induced CMP. After catheter ablation targeting parts of reentrant circuits, VT was not inducible in 8 (53%) of 15 patients with scar-related reentry, was modified in 5 (33%) patients, and still was inducible in 2 (13%) patients. Ablation was successful in 5 of 5 patients with bundle branch reentry and in 6 of 7 patients with a focal automaticity mechanism. Overall, catheter ablation abolished clinical recurrence of VT in 20 (77%) of 26 patients during a follow-up of 15 +/- 12 months. CONCLUSION: Three different mechanisms of VT are encountered in patients with nonischemic CMP. The mapping and ablation approach varies with the type of VT. In this selected population, the overall efficacy was 77%.     

动态基质标测在致心律失常右室心肌病患者室性心动过速射频消融中的应用

目的　探讨应用非接触球囊导管标测系统行动态基质标测,指导对致心律失常右室心肌病(ARVC)患者室性心动过速(室速)消融的价值。方法　应用非接触球囊导管标测系统在窦律下对 3例ARVC室速患者行动态基质标测,在确定室速的最早激动点、出口部位和传导顺序后,寻找与室速相关的峡部并行线性消融。结果　3例患者存在 3种不同形态的基质,分别位于右室流出道、右室前壁和右室前侧壁。共诱发 5种室速,平均心动周期为(348±65)ms,其中 3种室速起源于基质或基质边缘, 2种室速的起源远离基质; 1种室速经基质传导。5种室速全部消融成功。平均随访 20个月,无心动过速发作。结论　应用非接触球囊导管标测系统确定异常电生理基质有助于理解ARVC室速的发生机制和制定消融策略,行室速相关峡部的线性消融可有效治疗室速。     

Successful catheter ablation of two types of ventricular tachycardias triggered by cardiac resynchronization therapy: a case report

We report a case of a patient with nonischemic dilated cardiomyopathy and implantable cardioverter-defibrillator, in whom an upgrade to biventricular pacing triggered multiple episodes of ventricular tachycardias (VTs) of two morphologies. First VT presented as repetitive nonsustained arrhythmia of the same morphology as isolated ectopic beats, suggesting its focal origin. Second VT was reentrant and was triggered by the former ectopy, leading to a therapy from the device. Electroanatomical mapping of the left ventricle revealed relatively small low voltage area in the left ventricular outflow tract and identified both an arrhythmogenic focus as well as critical isthmus for reentrant VT. Radiofrequency catheter ablation successfully abolished both VTs. After the procedure, biventricular pacing was continued without any recurrences during a period of 24 months. The report emphasizes the role of catheter ablation in management of VTs triggered by cardiac resynchronization therapy.     

特发性左心室流出道心外膜侧室性心动过速

目的报道9例经电生理检查证实的特发性左心室流出道心外膜侧室性心动过速(室速)的体表心电图及电生理检查特点.方法男性5例,女性4例,年龄15～58岁,6例为运动诱发的持续性室速,3例为运动诱发的非持续性室速.结果室速时,9例体表心电图QRS波全部呈现右束支阻滞图形(8例胸前导联V1-V6呈现高R波),Ⅱ、Ⅲ、aVF导联为高R波,Ⅰ、aVL导联为QS波.电生理检查,右心室和左心室心内膜标测未发现最早心室激动点,在较早心室心内膜激动处的心内电图多呈现起始部低幅电位,提示远场电位.心室内起搏标测未发现与室速体表心电图12导联QRS波形态相同的起搏点.8例通过心脏静脉系统标测发现最早的心室激动点[体表心电图最早QRS波前15～50ms,平均(32±12)ms]和完全或近乎完全的起搏标测位于心大静脉的远端1例、心前间隔静脉的近端7例.1例患者在左心室流出道消融成功,1例患者在心大静脉远端血管内消融成功.其他患者在右心室和/或左心室内消融失败.结论心脏静脉标测可以鉴别出特发性左心室流出道心外膜侧室速.     

Tissue-specific variability in human epicardial impedance

Epicardial Impedance Mapping . Introduction: Epicardial ablation can be employed to treat ventricular tachycardia. Voltage attenuation in regions of fat can mimic epicardial scar, limiting its specificity. Ablation over fat may not be as effective. Prior animal data have shown that infarcted myocardium has lower impedance than normal, and human bioimpedance studies suggest peripheral fat displays higher impedance. Therefore, we tested the hypothesis that human epicardial fat has higher impedance than myocardium when measured with standard ablation tools. Methods: Patients undergoing elective surgery for coronary artery or valve disease were enrolled. A reference patch was placed on the patients’ back between the scapulae and connected to a standard RF generator (Stockert, GmBH, Germany). Impedance was measured by passing a 1 μA, 50 kHz current from the catheter tip to the patch. After sternotomy but before initiation of cardiopulmonary bypass, an ablation catheter (Celsius, Biosense Webster, Diamond Bar, CA, USA) was placed onto the epicardial surface in ventricular regions visually identified as fat or myocardium. At each site, impedance was recorded from the generator. Results: A total of 37 (7 patients) points were sampled. Impedance was significantly higher in regions of fat versus normal muscle (697 Ω vs. 301 Ω; P = 0.01). Moreover, normal sites from the LV had higher impedance than from the RV (381 Ω vs. 271 Ω; P = 0.01). Conclusions: Human epicardial fat has higher tissue impedance than normal muscle. Using epicardial impedance and voltage mapping in conjunction may improve differentiation of arrhythmia substrate from epicardial fat and improve the efficacy of epicardial ablation. (J Cardiovasc Electrophysiol, Vol. 22, pp. 436‐439)