右心室造影结合CARTO标测指引射频导管消融法洛四联症术后室性心动过速

目的:应用右心室造影结合电解剖标测（CARTO标测）指引经盐水灌注射频导管消融法洛四联症术后室性心动过速（VT）5例。方法: 5例患者中4例为男性,6～38岁,法洛四联症术后2～16年反复出现阵发性心悸,发病时体表心电图均表现为持续性VT且药物治疗无效,2例有晕厥史。均不同意放置埋藏式心脏复律除颤器（ICD）。应用右心室造影结合CARTO标测指引消融VT的方法如下:首先进行右心室造影明确右心室解剖及肺动脉瓣环位置,并作为解剖路标,在窦律时行右心室电压标测,标记低电压手术疤痕和室间隔补片区域,明确VT发生基质。而后心室程序电刺激诱发VT,如血流动力学稳定,则在VT时行拖带标测,确定并消融VT关键峡部;如血流动力学不稳定或不能诱发持续性VT,则在窦律时行起搏标测,在局部起搏时和VT有相同或相近的体表心电图并伴较长的刺激到QRS波时间的部位消融,并消融有晚电位或碎裂电位的电屏障区。结果: 5例患者可诱发出6种形态VT,VT周长230～310 ms,5种为持续性VT,其中1种血流动力学不稳定;另1种为非持续性VT。3例患者在VT时标测和消融,2例患者在窦律下标测后消融。6种形态VT均为疤痕折返机制,6种VT均消融成功。随访12～30月,无VT复发。结论: 右心室造影能明确法洛四联症术后右心室及肺动脉瓣环解剖结构,CARTO标测可以定位室间隔补片和外科手术疤痕,在明确这些VT发生基质基础上指引射频导管消融法洛四联症术后VT可取得较高的成功率。     

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。     

Carto标测指导下射频导管消融特发性右心室流出道室性心动过速

目的探讨Carto标测特发性右心室流出道室性心动过速(RVOT-VT)的方法和对射频导管消融(RFCA)的指导作用;分析RVOT-VT起源点与12导联心电图的关系,探讨12导联心电图对RVOT-VT起源点定位的辅助作用.方法14例特发性RVOT-VT患者,男性6例、女性8例,平均年龄(39.0±8.0)岁.所有病人均行常规电生理检查,对诱发室性心动过速(VT)或有频发室性早搏(PVCs)的病人,采用Carto标测VT或PVCs的最早激动点作为RFCA的靶点.如不能诱发VT或无频发PVCs患者,在窦性心律下标测RVOT的解剖结构,然后进行起搏标测,寻找起搏心电图与临床上VT或PVCs的心电图相同或相似的最佳起搏点作为RFCA的靶点.通过成功的RFCA确定每例VT起源点在RVOT的部位,然后分析每例VT起源点对应的12导联心电图特征.结果14例病人中,有8例病人手术时在基础状态下或静脉滴注异丙肾上腺素后有频发的PVCs,通过捕捉和标测PVCs重构RVOT的解剖结构和PVCs的电激动顺序,顺利地标出PVCs的最早激动点作为RFCA的靶点.另6例临床上有持续性VT的病人,有2例术中诱发出持续性VT.在VT状态下用Carto标测VT的最早激动点作为RFCA的靶点.2例只诱发短阵持续性VT和另2例只有在静脉滴注异丙肾上腺素后诱发出非持续性VT的患者,用起搏标测找出最佳消融靶点.所有14例RVOT-VT均成功地进行了RFCA,成功率为100%.VT起源于间隔部8例(57%),后壁4例(29%),外侧壁2例(14%).I、aVR和aVL导联上的QRS波形态有助于确定VT起源点在间隔部或游离壁;V3导联上的R/S比值有助于确定VT起源点在RVOT的上部或下部.结论Carto标测通过在VT或PVCs时行激动顺序标测或无VT和PVCs时行起搏标测可以准确地确定VT或PVCs的起源点,并有效地指导RFCA.VT或PVCs的12导联心电图有助于在术前定位VT或PVCs在RVOT的起源点.     

希浦系统起源IVT射频消融29例

目的探讨希浦系统起源左室特发室性心动过速(IVT)的标测方法与射频消融(RFCA)效果之间的关系.方法采用体表心电图(ECG)起搏标测法、心动过速标测法、窦性心律下P电位(浦肯野电位)标测法.结果 29例希浦系统起源左室特发室性心动过速全部经射频消融成功,随诊1个月～36个月无复发,心动过速标测消融组与窦性心律下P电位标测消融组在手术时间和X线曝光时间上比较无统计学意义,而起搏标测组与前两者比较有统计学意义(P＜0.05).结论①RFCA治疗希浦系统起源左室特发室性心动过速安全有效;②心动过速下标测消融与窦性心律下标测消融优于起搏标测.     

CARTO标测指导下射频消融治疗特发性右室流出道室性心动过速

目的探讨CARTO标测特发性右室流出道室速(RVOT-VT)的方法和对射频消融(RFCA)的指导作用;分析RVOT-VT起源点与12导联心电图的关系,探讨12导联心电图对RVOT-VT起源点定位的辅助作用.方法14例特发性RVOT-VT患者,男性6例、女性8例,平均年龄39.0±8.0岁.所有病人均行常规电生理检查,对诱发室性心动过速(VT)或有频发室性早搏(PVCs)的病人,采用CARTO标测VT或PVCs的最早激动点作为RFCA的靶点.如不能诱发VT或无频发PVCs患者,在窦性心律下标测RVOT的解剖结构,然后进行起搏标测,寻找起搏ECG与临床上VT或PVCs的ECG相同或相似的最佳起搏点作为RFCA的靶点.通过成功地RFCA确定每例VT起源点在RVOT的部位,然后分析每例VT起源点对应的12导联心电图特征.结果14例病人中,有8例病人手术时在基础状态下或静滴异丙肾上腺素后有频发的PVCs,通过捕捉和标测PVCs重构RVOT的解剖结构和PVCs的电激动顺序,顺利地标出PVCs的最早激动点作为RFCA的靶点.另6例临床上有持续性VT的病人,有2例术中诱发出持续性VT.在VT状态下用CARTO标测VT的最早激动点作为RFCA的靶点.2例只诱发短阵持续性VT和另2例只有在静滴异丙肾上腺素后诱发出非持续性VT的患者,用起搏标测找出最佳消融,靶点.所有14例RVOT-VT均成功地进行了RFCA,成功率为100%.VT起源于间隔部8例(58%),后壁4例(28%),外侧壁2例(14%).Ⅰ、aVL和aVR导联上的QRS波形态有助于确定VT起源点在间隔部或游离壁;V3导联上的R/S比值有助于确定VT起源点在RVOT的上部或下部.结论CARTO标测通过在VT或PVCs时行激动顺序标测或无VT和PVCs时行起搏标测可以准确地确定VT或PVCs的起源点,并有效地指导RFCA.VT或PVCs的十二导联心电图有助于在术前定位VT或PVCs在RVOT的起源点.     

射频导管消融心肌梗死后浦肯野纤维参与的室性心动过速

目的 报道心肌梗死(MI)后浦肯野纤维参与室性心动过速(VT)的电生理机制和射频导管消融.方法 3例男性患者,55 ～75岁,前壁MI经抗心律失常药物和/或血运重建治疗后,仍反复发作VT/室性早搏(PVC),呈右束支阻滞(RBBB)图形伴心电轴左偏或右偏.左心室射血分数0.44～0.61.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VT/PVC.结果 例1和例2程序性心室刺激反复诱发出持续性临床VT,例3术中自发非持续性临床VT/频发PVC.3例VT的标测结果均不符合典型MI后瘢痕折返性VT,均在VT/PVC时,在后间隔低电压区边缘标测到最早浦肯野电位(PP)或舒张期电位(DP)提前体表QRS波-20 ～ -70 ms处消融VT/PVC成功.结论 MI后可以发生浦肯野纤维参与的单形性VT,可以发生在MI后急性缺血时期,也可发生在MI后远期,其电生理特性、标测和射频导管消融与特发性左心室分支性VT相近,射频导管消融可有效根除或控制此类VT.     

心室反应在射频消融特发性室性心动过速中作用的临床研究

目的　探讨心室反应 (VR)在射频消融IVT的作用。方法　应用体表心电图、心内膜激动标测及VR相结合的方法射频消融 13例IVT病人。以激动标测初选靶点 ,射频消融试放电产生的VR确定靶点 ,采用VR与VT发作相一致处为靶点消融。结果　 13例IVT即刻消融成功率 13/ 13。VR表现 :(1)窦性心律下消融时出现与VT发作相一致的VR。随后室性心动过速 (VT)中间断出现窦性心律、双发或联律室性早搏 ,最终完全恢复成窦性心律。 (2 )出现与VT发作不一致的VR。结论　以VR与VT发作相一致处作靶点 ,产生与VT发作相一致的VR可被视为有效消融的指标。     

三维标测系统指导下导管射频消融治疗难治性心律失常6例

目的 评价三维标测(Carto)系统指导下导管射频消融治疗的难治性心律失常安全性和有效性.方法 术中运用Carto重建肺静脉和心房的模拟三维结构图像, 心房颤动在左右肺静脉口周围0.5 cm～1.0 cm处作环形电隔离,由三维标测系统监测消融路径是否连续.心房扑动病人在心动过速折返环的关键峡部行线性消融,并以冷肝素盐水灌注导管,术后随访观察.结果 6例消融病人, 2例随访5个月无复发,1例于术后第3天出现1次阵发性心房颤动,另3例病人术后均无任何不适,体表心电图显示为窦性心律目前仍在随访中.结论 应用Carto系统指导导管射频消融难治性心律失常治疗安全有效.     

单纯碎裂电位指导心房颤动消融的初步临床观察

目的探讨碎裂电位指导心房颤动（房颤）射频导管消融的可行性。方法22例药物治疗无效有症状的房颤患者（阵发性16例,持续性6例）,在自发或诱发房颤时,用Carto构建左心房或左、右心房的三维模型并标测、消融碎裂电位,终点是消除标测到所有碎裂电位或转复窦性心律。结果碎裂电位消融后,13例（59％）转复为窦性心律（直接转复7例,先转为房性心动过速（房速）／心房扑动（房扑）然后转复6例）,9例消融未转复窦性心律患者行电复律或药物复律成功。6例复发（5例房速／房扑,1例阵发性房颤）再次消融,5例成功,随访3—18（10．9±4．8）个月,共有16例（73％）无快速房性心律失常事件,碎裂电位主要分布于左侧房间隔、肺静脉周围、左心房顶部。碎裂电位消融后房颤终止前房颤周期与碎裂电位消融前相比明显延长[（157±18）ms vs （211±32）ms,P〈0．05]。除一例发生心脏压塞且心包穿刺成功引流外,无消融术相关的并发症和后遗症。结论碎裂电位指导房颤导管射频消融安全有效可行。     

器质性心脏病室性心动过速导管消融治疗进展

器质性心脏病瘢痕相关性室性心动过速（室速）的发生主要是折返机制,目前多采用心脏三维标测系统指引下对耐受性好、血流动力学稳定的室速激动标测消融,对于血流动力学不稳定的室速,窦性心律下基质标测、电压图判断室速的解剖基质,结合起搏标测和拖带标测技术识别室速的折返环,盐水灌注导管消融治疗;近年来不断积累有关临床循证证据、适应证进一步拓展、新的标测消融和辅助技术临床上应用,取得了新的进展。     

Relationship between successful ablation sites and the scar border zone defined by substrate mapping for ventricular tachycardia post-myocardial infarction

INTRODUCTION: It is unknown if identification of scar border zones by electroanatomical mapping correlates with successful ablation sites determined from mapping during ventricular tachycardia (VT) post-myocardial infarction (MI). We sought to assess the relationship between successful ablation sites of hemodynamically stable post-MI VTs determined by mapping during VT with the scar border zone defined in sinus rhythm. METHODS AND RESULTS: Forty-six patients presenting with hemodynamically stable, mappable monomorphic VT post-MI and who had at least one such VT successfully ablated were prospectively included in the study. In each patient, VT was ablated by targeting regions during VT that exhibited early activation, +/- isolated mid-diastolic potentials, and concealed entrainment suggesting a critical isthmus site. Prior to ablation, a detailed sinus-rhythm CARTO voltage map of the left ventricle was obtained. A voltage <0.5 mV defined dense scar. Successful VT ablation sites were registered on the sinus voltage map to assess their relationship to the scar border zone. Of the 86 VTs, 68% were successfully ablated at sites in the endocardial border zone. The remaining VTs had ablation sites within the scar in (18%), in normal myocardium (4%), and on the epicardial surface (10%). There were no significant differences in VT recurrence amongst the different groups. CONCLUSION: Successful ablation sites of hemodynamically stable, monomorphic VTs post-MI are often located in the scar border zone as defined by substrate voltage mapping. However, in a sizable minority, ablation sites are located within endocardial scar, epicardially, and even in normal myocardium.     

Catheter Ablation of Recurrent Scar-Related Ventricular Tachycardia Using Electroanatomical Mapping and Irrigated Ablation Technology: Results of the Prospective Multicenter Euro-VT-Study

Catheter Ablation of Ventricular Tachycardia.   Introduction: Ventricular tachycardia (VT) late after myocardial infarction is an important contributor to morbidity and mortality. This prospective multicenter study assessed the efficacy and safety of electroanatomical mapping in combination with open-saline irrigated ablation technology for ablation of chronic recurrent mappable and unmappable VT in remote myocardial infarction.
Methods and Results: In 8 European institutions, 63 patients (89% males) were enrolled in the study. All patients had remote myocardial infarction and presented with a median number of 17 (range 1–380) VTs in the preceding 6 months. Incessant VT was present in 14 patients (22%). Left ventricular ejection fraction measured 30 ± 13%. A mean of 3 VTs were targeted per patient and 22% of all patients had only unmappable VT. The mean follow-up period was 12 ± 3 months. A total of 164 VTs were targeted during catheter ablation. Ablation was acutely successful in 51 patients (81%). One patient (1.5%) experienced a major complication with degeneration of VT into ventricular fibrillation necessitating cardiopulmonary resuscitation maneuvers. However, no death occurred acutely or within the first 30 days after catheter ablation. During the follow-up, 19 of the initially successful ablated patients (37%) and 31 of all ablated patients (49%) developed some type of VT recurrence.
Conclusions: The results of this multicenter study demonstrate the high acute success rate and a low complication rate of irrigated tip catheter ablation of all clinical relevant VTs in remote myocardial infarction. However, during the follow-up a relevant number of recurrences occurred. (J Cardiovasc Electrophysiol, Vol. 21, pp. 47–53, January 2010)     

室性心动过速的基质标测与消融

目的 探讨使用Carto三维系统标测致心律失常性右心室心肌病(ARVD/C)室性心律失常的基质来指导导管消融的安全性和有效性.方法 自2007年7月至2008年4月,北京大学第一医院心内科连续收治4例ARVD/C患者,年龄28～53岁,男性3例,女性1例,其中1例患者有直系亲属猝死家族史,发作性室性早搏/室性心动过速(VT)病史3个月至24年.使用Carto三维系统进行电解剖电压标测,局部电压低于1.5 mV的区域判断为病变心肌,低于0.5 mV的区域为瘢痕区,结合传统的激动顺序标测、起搏标测、拖带标测和心室内碎裂电位,识别病变心肌范围和心动过速折返路径以指导消融.结果 4例患者电生理检查共诱发出7种形态的左束支阻滞形、VT,电解剖电压标测的低电压区主要位于右心室流人道的基底部和偏间隔部,在病变心肌与正常心肌交界区和/或环绕病变心肌的最早激动处做线性消融,4例患者均获消融即刻成功,无并发症.4例患者消融术后随访3个月至1年,有1例出现复发,口服胺碘酮控制,至今无晕厥和猝死.结论 ARVD/C的VT标测与消融安全可靠,应用三维系统进行电解剖电压标测与传统的心电标测方式相结合,可更精确判断ARVD/C的室性心律失常基质和有效提高消融成功率.     

Strategies for catheter ablation of scar-related ventricular tachycardia

Ventricular tachycardia (VT) due to reentry in and around regions of ventricular scar from an old myocardial infarction or cardiomyopathic process is often a difficult management problem. Radiofrequency catheter ablation is an option for controlling frequent VT episodes. Patient and VT characteristics determine the mapping and ablation approach and efficacy. In patients with a VT that is hemodynamically tolerated to allow mapping, prevention of recurrent VT is achieved in 54% to 66% of patients with a procedure related mortality of 1% to 2.7%. Multiple morphologies of monomorphic VT and circuits that are located deep to the endocardium are common problems that reduce efficacy. Mapping to identify target regions for ablation can be difficult if VT is rapid and not tolerated, or not inducible. Ablation of these “unmappable VTs” by designing ablation lines or areas based on the characteristics of the scar as assessed during sinus rhythm, and using approaches to assess global activation from a limited number of beats has been shown to be feasible. Ablation of multiple VTs, epicardial VTs, and poorly tolerated VTs are feasible. Future studies defining efficacy and risks are needed.     

Use of a saline-irrigated tip catheter for ablation of ventricular tachycardia resistant to conventional radiofrequency ablation: early experience

INTRODUCTION: Radiofrequency (RF) catheter ablation of ventricular tachycardia (VT) may fail if the critical isthmus is located intramyocardially or epicardially. The design of a saline-irrigated tip (SIT) catheter (Thermo-Cool, Cordis-Webster) involves active cooling of the tip electrode, which allows creation of larger ablation lesions. METHODS AND RESULTS: Eight patients (6 men, age 59 +/- 12 years) in whom the clinical target VT (cycle length 430 +/- 97 msec) could not be ablated using a conventional 4-mm tip RF ablation catheter underwent additional attempts to ablate this VT using a SIT catheter. Six patients had an old myocardial infarction, 1 patient had a dilated cardiomyopathy, and 1 patient had a structurally normal heart. Ablation of the clinical target VT using a SIT catheter was attempted from the left ventricle in 6 (septal, posterobasal, and inferior: 2 each) and from the right ventricle in 2 patients (both septal), by entrainment (n = 6), activation (n = 1), or pace mapping (n = 1). A mean of 6 +/- 5 (range 2 to 15) pulses were delivered. Target VT ablation was successful in 5 patients (63%). After successful ablation, at a mean follow-up of 6.5 +/- 4 months and while taking antiarrhythmic drugs, all 5 patients were free of VT recurrences. CONCLUSION: The clinical target VT could be ablated using a SIT catheter in 5 (63%) of the 8 patients in whom ablation using a conventional RF catheter was unsuccessful. In the 2 patients with septal VT, a biventricular approach to mapping and ablation was required.     

Radiofrequency catheter ablation in symptomatic ventricular arrhythmia

Background: Radiofrequency catheter ablation (RFCA) is an effective method to cure both supraventricular and ventricular arrhythmia (VA) in certain centres.
Aim: To assess the results of RFCA in VA at Siriraj Hospital.
Method: Electrophysiologic study, mapping, using both earliest endocardial activation and pace mapping, and ablation were performed.
Results: Thirty patients with symptomatic VA underwent RFCA. The mean age was 44 years. Eight patients had underlying heart disease (two prolapsed mitral valve, three myocarditis, two dilated cardiomyopathy and one mitral stenosis). Thirty-six morphologies of VA were detected from the study. Thirty-three morphologic tachycardias attempted were successfully ablated; 17, 10 and six were right VT, left VT and premature ventricular contraction (PVC), respectively. Failure of ablation occurred in one patient with left VT. Only minor complications occurred in this study.
There was no difference in cycle length and endocardial activation time between right and left VT. 12/12 identical pace mapping was more easily performed in right VT than in left VT The fluoroscopic and procedure times in left VT were significantly longer than in right VT.
Relapse occurred in six patients. Re-ablation was successfully performed in four patients, giving a final success rate of 93%.     

Multielectrode contact mapping to assess scar modification in post-myocardial infarction ventricular tachycardia patients

Substrate-based approaches for ablation of unmappable ventricular tachycardia (VT) are strictly dependent on high-density mapping of the scar. Ultra-high-density mapping with multielectrode catheters facilitates an accurate and faster definition of sites critical for re-entry, due to the possibility of simultaneous recordings of local potential from different pairs of electrodes. Multipolar catheters can be advanced to map the endocardial or the epicardial surface. A strong correlation between the scar area determined by electraoanatomical mapping and the histopathological scar size has been demonstrated. A double-transeptal technique allows for an accurate definition of target sites. The complex scar architecture has been investigated by ultra-high-density mapping, let the identification of islets of heterogeneity where electrograms adjacent to the preserved myocardium have an higher incidence of late potentials. Pacing manoeuvres can easily be performed from any pair of electrode, to demonstrate the involvement of late potentials into the VT circuit. This strategy allows for a clear-cut validation of late potential abolishment, and may offer advantages to shorten procedural and fluoroscopy times. Large series are necessary to definitively assess the potential role of multielectrode mapping as a guide for the substrate ablation approach in post-myocardial infarction VT patients.     

Mechanical interruption of postinfarction ventricular tachycardia as a guide for catheter ablation

BACKGROUND: Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma. OBJECTIVES: The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma. METHODS: A consecutive series of 39 patients (mean age 68 +/- 7 years, ejection fraction 0.25 +/- 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 +/- 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization. RESULTS: In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 +/- 56 ms vs 253 +/- 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 +/- 11 months. CONCLUSIONS: Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.     

Magnetic resonance-based anatomical analysis of scar-related ventricular tachycardia: implications for catheter ablation

In catheter ablation of scar-related monomorphic ventricular tachycardia (VT), substrate voltage mapping is used to electrically define the scar during sinus rhythm. However, the electrically defined scar may not accurately reflect the anatomical scar. Magnetic resonance-based visualization of the scar may elucidate the 3D anatomical correlation between the fine structural details of the scar and scar-related VT circuits. We registered VT activation sequence with the 3D scar anatomy derived from high-resolution contrast-enhanced MRI in a swine model of chronic myocardial infarction using epicardial sock electrodes (n=6, epicardial group), which have direct contact with the myocardium where the electrical signal is recorded. In a separate group of animals (n=5, endocardial group), we also assessed the incidence of endocardial reentry in this model using endocardial basket catheters. Ten to 12 weeks after myocardial infarction, sustained monomorphic VT was reproducibly induced in all animals (n=11). In the epicardial group, 21 VT morphologies were induced, of which 4 (19.0%) showed epicardial reentry. The reentry isthmus was characterized by a relatively small volume of viable myocardium bound by the scar tissue at the infarct border zone or over the infarct. In the endocardial group (n=5), 6 VT morphologies were induced, of which 4 (66.7%) showed endocardial reentry. In conclusion, MRI revealed a scar with spatially complex structures, particularly at the isthmus, with substrate for multiple VT morphologies after a single ischemic episode. Magnetic resonance-based visualization of scar morphology would potentially contribute to preprocedural planning for catheter ablation of scar-related, unmappable VT.