Demonstration of the reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia: direct evidence for macroreentry as the underlying mechanism

The exact reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) remains unclear. This case report demonstrates the reentrant circuit of ILVT. A 20-pole electrode catheter was placed along the left posterior fascicle during electrophysiologic study. ILVT was reproducibly induced by programmed ventricular stimulation. During the tachycardia, sequential diastolic potentials bridging the entire diastolic period were observed in the recordings from the electrodes positioned from left ventricular mid-septum to inferoapical septum. The slow conduction zone appeared to be composed of a false tendon in this patient. Entrainment of the ILVT from the right ventricular outflow tract at a different pacing cycle length revealed that a dominant conduction delay occurred at the proximal site of the slow conduction zone. Entrainment studies from several sites on the left ventricular septum confirmed that these sites where sequential electrical activity was recorded were included within the reentrant circuit. However, the left posterior fascicle itself seemed to be a bystander. This report provides the direct evidence of macroreentry as the underlying mechanism of this ILVT, adjacent to the left posterior fascicle.     

Dual Morphology of Idiopathic Ventricular Tachycardia

INTRODUCTION: Idiopathic ventricular tachycardia (VT) typically has a single morphology originating either in the right ventricular outflow tract (RVOT) or near the posterior fascicle of the left ventricle (LV) in most instances. We present our observations in six patients with idiopathic VT in whom two morphologies were present. METHODS AND RESULTS: Of 55 patients with idiopathic VT who underwent radiofrequency (RF) ablation, 44 had LV "fascicular" tachycardia, whereas 11 had RVOT tachycardia. During RF energy delivery, there was a change in VT morphology in two patients with idiopathic LV tachycardia. This second morphology was not ablated initially, recurred at follow-up, and was reablated successfully. In two additional patients with idiopathic LV tachycardia, a second VT was inducible after ablation of the "clinical" VT. This second morphology recurred at follow-up and was ablated successfully in one patient. The site where the second VT was ablated in all the three patients was remote from that of the first VT. In two patients with RVOT tachycardia, a second VT, originating from a different area of the RVOT, was induced after RF ablation of the "clinical" VT. This second VT recurred at follow-up and was reablated successfully in one patient. CONCLUSION: Idiopathic VT is a more heterogenous entity than hitherto believed. A second VT was seen in 11% of patients during or after RF ablation of the "clinical" VT. The appearance of a second VT suggests either a different exit site of the same circuit or another site of origin.     

左室特发性室性心动过速常规方法消融困难的线性消融

目的:探讨在常规方法消融困难的左室特发性室性心动过速（ILVT）患者中室间隔左室面线性消融的有效性。方法: 18例术中不能诱发持续性心动过速或发作时不能耐受患者,进行室间隔左室面心尖到心底部连线的前1/3～1/2区域,在窦性心律下首先标到蒲肯野氏纤维电位（PP）,向下至室间隔与左室下壁交界、向上至前后间隔中线进行线性消融,术后门诊或电话随访。结果: 所有患者术后即刻均未能诱发出ILVT。随访3~35（23±13）个月,3例/18例（17%）复发,远期成功率达83%,无1例发生永久性的并发症。结论: 对于术中不能诱发持续性心动过速或发作时不能耐受的ILVT患者,室间隔左室面线性消融安全有效,可以作为补救性消融措施。     

Verapamil-Sensitive Left Anterior Fascicular Ventricular Tachycardia: Results of Radiofrequency Ablation in Six Patients

Verapamil-Sensitive Left Anterior Fascicular VT. Introduction: Verapamil-sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left-axis deviation bas been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil-sensitive VT with an RBBB configuration and right-axis deviation is rare, and may originate in the left anterior fascicle. Methods and Results: Six patients (five men and one woman, mean age 54 ± 15 years) with a history of sustained VT with an RBBB configuration and right-axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid-anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow-up (mean 32 ± 9 months), one patient in the group of ablation at the VT exit bad sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left-axis deviation. Conclusion: Verapamil-sensitive VT with an RBBB configuration and right-axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.     

Radiofrequency catheter ablation of coexistent atrioventricular reciprocating tachycardia and left ventricular tachycardia originating in the left anterior fascicle

Coexistence of supraventricular tachycardia and ventricular tachycardia is rare. A patient with no structural heart disease and wide QRS complex tachycardia with a right bundle block configuration and right-axis deviation underwent electrophysiological examination. A concealed left atrioventricular pathway (AP) was found, and atrioventricular reciprocating tachycardia (AVRT) and left ventricular tachycardia (VT) originating in or close to the anterior fascicle of the left ventricle were both induced. Radiofrequency (RF) catheter ablation of the concealed left AP was successfully performed. Ten months later, VT recurred and was successfully ablated using a local Purkinje potential as a guide. Coexistent AVRT and idiopathic VT originating from within or near the left anterior fascicle were successfully ablated.     

Ventricular tachycardia with participation of the left bundle-Purkinje system in patients with structural heart disease: identification of slow conduction during sinus rhythm

Introduction: Idiopathic left ventricular tachycardia (VT) originating from the left posterior fascicle can be eliminated by ablation at sites with abnormal diastolic potentials (DPs) during sinus rhythm. We investigated whether such DPs can also be recorded in patients with structural heart disease and VT involving the left bundle-Purkinje system.
Methods and Results: Eight patients (mean age 67 ± 11 years) with nonischemic cardiomyopathy (n = 5) or prior myocardial infarction (n = 3) presented with VT involving the left bundle-Purkinje system (cycle length 376 ± 45 ms). Three types of VT were observed: macroreentrant VT with participation of both left bundle fascicles in three patients, fascicular VT involving the left posterior fascicle in two patients, and scar-related VT with Purkinje fibers as part of the reentrant circuit in three patients. In all patients, abnormal isolated DPs of low amplitude with a QRS—earliest DP interval of 374 ± 86 ms were found during sinus rhythm in the mid- or inferior left ventricular septum in areas with Purkinje potentials. The abnormal DPs during sinus rhythm coincided or were in proximity to DPs during the VT in six patients. VT ablation targeting the sites with the earliest abnormal DPs during sinus eliminated the VT in 7 of 8 patients with freedom from VT recurrence in six patients during the follow-up of 11 ± 5 months.
Conclusions: Isolated DPs during sinus rhythm were found in proximity to the posterior Purkinje network in patients with VT involving the left bundle-Purkinje system associated with heart disease and can be used to guide successful catheter ablation.     

First Case of Left Posterior Fascicle in a Bystander Circuit of Idiopathic Left Ventricular Tachycardia

We describe a case of idiopathic left ventricular tachycardia in which the left posterior fascicle was clearly delineated to be a bystander in a re-entry circuit, with participation of the left interventricular myocardium as the retrograde limb instead. To the best of our knowledge, this is the first case report that has directly proven the left posterior fascicle to be a bystander during idiopathic left ventricular tachycardia.     

Cure of Interfascicular Reentrant Ventricular Tachycardia by Ablation of the Anterior Fascicle of the Left Bundle Branch

Ablation of Interfascicular Reentrant Tachycardia. Introduction: Fascicular reentrant ventricular tachycardia (VT) using the anterior fascicle of the left bundle anterogradely is rare and may produce identical QRS morphology during sinus rhythm and VT. Catheter ablation of this type of VT has not been described in detail.
Methods and Results: In a postinfarct patient with dilated left ventricle and recurrent VT (showing a QRS configuration of right bundle branch, left posterior fascicular block), endocardial recordings from the His-Purkinje system showed that VT was due to interfascicular reentry. Induction of VT occurred after progressive retrograde conduction delay on increasing the prematurity of the extrastimulus. Anterograde conduction occurred exclusively over the left anterior fascicle, which caused identical QRS morphology during sinus rhythm and VT. During VT, the left posterior fascicle was used retrogradely. The usual target for bundle branch reentry ablation, the right bundle, did not participate in the reentrant circuit. While performing left ventricular endocardial mapping, VT was interrupted when positioning the catheter on the left anterior fascicle, and "reversed" nonsustained bundle branch reentry occurred with anterograde conduction over the posterior fascicle and retrograde conduction over the anterior fascicle. Ablation of conduction in the anterior fascicle led to cure of the VT.
Conclusion: Interfascicular reentrant VT with right bundle branch block, right-axis QRS configuration can be cured by catheter ablation of anterior fascicle conduction.     

Ventricular arrhythmias in normal hearts

Idiopathic ventricular tachycardia (VT) is characterized by two predominant forms. The most common form originates from the right ventricular outflow tract and presents as repetitive monomorphic VT or exercise-induced VT. The tachycardia is adenosine sensitive and is thought to be because of cAMP-mediated triggered activity. The other major form of idiopathic VT is owing to verapamil-sensitive intrafascicular re-entrant tachycardia, which most often originates in the region of the left posterior fascicle. Both forms of idiopathic VT can be readily treated with radiofrequency catheter ablation.     

Findings on magnetic resonance imaging of fascicular ventricular tachycardia

Background

Idiopathic left ventricular tachycardia (ILVT) with right bundle branch block and left axis deviation originates from the left posterior fascicle—Purkinje fiber network. Scar-related ventricular tachycardias (VTs) with Purkinje fibers as a part of the reentry circuit have also been described in patients with structural heart disease.

Methods and results

Nine patients with fascicular VT (left posterior, n?=?8; left anterior, n?=?1) with preserved left ventricular ejection fraction (60?±?10 %) underwent cardiac magnetic resonance imaging (MRI) including functional analysis and delayed enhancement magnetic resonance imaging (DE-MRI). No definite structural abnormalities were detected by DE-MRI in four patients. DE-MRI revealed unifocal or multifocal areas of fibrosis or scar in three patients corresponding to the regions where typical Purkinje potentials guided successful ablation of the sustained fascicular VT. A false tendon extending from the free wall to the septum was found in one patient. Moderate reduction of left ventricular ejection fraction associated with septal or multifocal left ventricular fibrosis was detected in two patients with ventricular bigeminy originating from the left posterior fascicle. During the follow-up of 29?±?22 months after successful catheter ablation in the nine patients, one patient with septal fibrosis detected by DE-MRI had VT recurrence and received an implantable cardioverter defibrillator.

Conclusion

Detection of local areas of fibrosis or scar by DE-MRI may help to distinguish idiopathic fascicular tachycardia from scar-related fascicular VT in patients with preserved left ventricular function.     

Radiofrequency Catheter Ablation of Idiopathic Left Ventricular Tachycardia:

Idiopathic Left Ventricular Tachycardia. Introduction: Idiopathic left ventricular tachycardia with a QRS pattern of right bundle branch block and left-axis deviation constitutes a rare but electrophysiologically distinct arrhythmia entity. The underlying mechanism of this tachycardia, however, is still a matter of controversy. This report describes findings in a 42-year-old man who underwent successful radiofrequency catheter ablation of idiopathic left ventricular tachycardia.
Methods and Results: On electrophysiologic study, the tachycardia was reproducibly induced and terminated with double ventricular extrastimuli. Intravenous verapamil terminated the tachycardia whereas adenosine did not. Detailed left ventricular catheter mapping during sinus rhythm revealed a fragmented delayed potential at the mid-apical region of the inferior site near the posterior fascicle of the left bundle branch. At the same site, continuous electrical activity throughout the entire cardiac cycle was recorded during ventricular tachycardia. Repeated spontaneous termination of this continuous electrical activity in late diastole was followed immediately by termination of the tachycardia. Single application of radiofrequency current for 20 seconds at this site completely abolished inducibility of the tachycardia. After catheter ablation, at the identical site of preablation recording of the fractionated potential during sinus rhythm, no fragmented delayed activity could be recorded. There was no complication from the ablation procedure.
Conclusion: The preablation recordings of fragmented delayed potentials during sinus rhythm and continuous diastolic electrical activity during tachycardia, together with ablation characteristics and previously reported electrophysiologic properties of this arrhythmia, may further support microreentry as the underlying mechanism in idiopathic left ventricular tachycardia.     

电解剖标测消融左室特发性室性心动过速

目的报道三维电解剖标测指导下左室特发性室性心动过速(ILVT)的射频消融方法。方法4例经常规电生理标测消融失败的ILVT患者,应用三维电解剖(CARTO)标测指导确定消融部位。结果4例患者室性心动过速时CARTO标测的V波最早激动点在前中间隔,在此部位消融无效。以左后分支电位标测的最早激动点在左后间隔区域,在此部位消融终止所有ILVT,此成功部位距V波最早记录点1.0~2.0cm。随访1~7个月无复发。结论左后分支及其浦氏纤维是构成折返环的关键部位,也是射频消融的关键部位,并与折返的出口有一定距离。     

Left bundle branch block-type ventricular tachycardia originating from the left ventricular septum in a patient with cardiac sarcoidosis

This case report describes a left bundle branch block (LBBB)-type ventricular tachycardia (VT) with a unique reentrant circuit in a patient with cardiac sarcoidosis. The VT morphology and pace mapping supported an exit site of the VT from the basal posterior right ventricle (RV) septum. Nonetheless, concealed entrainment was established by pacing from a septal left ventricular (LV) site recording a diastolic potential, opposite site to the RV site. A point ablation at that LV site could successfully terminate the VT, suggesting that a critical isthmus was located on the LV side of the interventricular septum despite the demonstration of an LBBB-type VT.     

Novel mechanism of postinfarction ventricular tachycardia originating in surviving left posterior Purkinje fibers

BACKGROUND: Other than bundle branch reentry and interfascicular reentry, monomorphic postmyocardial infarction (post-MI) reentrant ventricular tachycardia (VT) including the His-Purkinje system has not been reported. Verapamil-sensitive idiopathic left VT includes the left posterior Purkinje fibers but develops in patients without structural heart disease. OBJECTIVES: The purpose of this study was to describe a novel mechanism of reentrant VT arising from the left posterior Purkinje fibers in patients with a prior MI. METHODS: The study consisted of four patients with a prior MI and symptomatic heart failure who underwent electrophysiologic study and catheter ablation for VT showing right bundle branch block (n = 3) or atypical left bundle branch block (n = 1) morphology with superior axis. In two patients, the VT frequently emerged during the acute phase of MI and required emergency catheter ablation. RESULTS: Clinical VT was reproducibly induced by programmed stimulation. In three patients, both diastolic and presystolic Purkinje potentials were sequentially recorded along the left ventricular posterior septum during the VT, whereas in the fourth patient, only presystolic Purkinje potentials were observed. During entrainment pacing from the right atrium, diastolic Purkinje potentials were captured orthodromically and demonstrated decremental conduction properties, whereas presystolic Purkinje potentials were captured antidromically and appeared between the His and QRS complex. Radiofrequency energy delivered at the site exhibiting a Purkinje-QRS interval of 58 +/- 26 ms successfully eliminated the VTs without provoking any conduction disturbances. CONCLUSION: Reentrant monomorphic VT originating from the left posterior Purkinje fibers, which is analogous to idiopathic left VT, can develop in the acute or chronic phase of MI. Catheter ablation is highly effective in eliminating this VT without affecting left ventricular conduction.     

Retrograde Purkinje Potential Activation During Sinus Rhythm Following Catheter Ablation of Idiopathic Left Ventricular Tachycardia

Idiopathic Left VT and Purkinje Potentials . We describe two patients with idiopathic left ventricular tachycardia that were cured by radiofrequency catheter ablation. Tachycardia was inducible by ventricular stimulation and was verapamil sensitive. Two distinct presystolic potentials (PI and P2) were recorded during tachycardia in the mid-septal or inferoapical area, but only one potential (P2) was recorded during sinus rhythm. After catheter ablation at this site, the PI potential was noted after the QRS complex during sinus rhythm, while the P2 was still observed before the QRS complex. The P1 potential showed a decremental property during atrial or ventricular pacing. These data suggest that Purkinje tissue with decremental properties was responsible for the tachycardia mechanism, and that the reentry circuit involving this tissue is likely to be of considerable size.     

The radio frequency catheter ablation of inter-fascicular reentrant tachycardia: new insights into the electrophysiological and anatomical characteristics

Introduction

Macro-reentrant ventricular tachycardias (VT) utilizing the bundle branches and Purkinje fibers have been reported as verapamil sensitive VT (idiopathic left VT), bundle branch reentrant VT (BBRT) and inter-fascicular reentrant tachycardia (inter-fascicular VT). However, diagnostic confusion exists with these VTs due to the difficulty in differentiating between them with conventional electrophysiological (EP) studies. The aim of this study was to clarify the EP and anatomical entity of inter-fascicular VT, and provide successful methods for the radio frequency catheter ablation (RFCA) of inter-fascicular VT.

Methods and results

A total of nine patients were included in this study. All patients were diagnosed with idiopathic left VT in the first session, and underwent a second session after a failed RFCA. Detailed EP studies guided by a three-dimensional (3D) mapping system were performed to further analyze the VTs. All VTs were finally diagnosed as inter-fascicular VT. They were successfully cured with RFCA targeting the left anterior or posterior fascicle, which was regarded as a requisite part of the reentrant circuit of the inter-fascicular VT, using 3D and fluoroscopic images combined with a detailed EP investigation instead of the conventional RFCA method targeting Purkinje potentials for the RFCA of idiopathic left VT.

Conclusions

Inter-fascicular VT could be misdiagnosed as idiopathic left VT due to the limitations of the conventional EP study. Failed RFCA in presumptive idiopathic left VT cases has to be carefully investigated by further analysis, and a tailored RFCA strategy targeting the requisite portions of the left fascicles in the inter-fascicular VT reentrant circuit will be required for the successful elimination of the inter-fascicular VT.     

Radiofrequency catheter ablation of upper septal idiopathic left ventricular tachycardia exhibiting left bundle branch block morphology

Idiopathic left ventricular (LV) tachycardia usually exhibits right bundle branch block morphology. There are only a few sporadic cases that exhibit left bundle branch block (LBBB) morphology. We report a patient whose QRS complex during ventricular tachycardia (VT) was relatively narrow (100 msec) and exhibited LBBB (precordial R wave transition between V3 and V4) and a normal frontal plane axis. This VT was ablated successfully by radiofrequency current applied to the LV upper septum, where the earliest endocardial activation was recorded.     

Catheter Ablation of Idiopathic Left Ventricular Tachycardia with Multiple Breakthrough Sites Guided by an Electroanatomical Mapping System

Idiopathic ventricular tachycardia (VT) has been considered to be amenable to radiofrequency catheter ablation guided by Purkinje potentials. However, there appear to be various types of reentrant circuits associated with this VT deduced from the results of the successful radiofrequency catheter ablation cases. We describe in this report a patient with idiopathic left ventricular tachycardia which was electrically inducible and verapamil sensitive. Multiple earliest ventricular activation sites during tachycardia were detected with electroanatomical mapping using the CARTO system. Multiple applications at these sites failed to eliminate the VT. The earliest Purkinje potential was recorded at least 1.5[emsp4 ]cm away from the earliest ventricular activation sites, and the radiofrequency current application at this site resulted in the complete abolition of this VT. The reentrant circuit of this tachycardia seemed to have multiple breakthrough sites to the ventricular myocardium, which were distant from the requisite part of the reentrant circuit of this VT involving the Purkinje fiber network conduction system.     

Different Forms of Ventricular Tachycardia Involving the Left Anterior Fascicle in Nonischemic Cardiomyopathy: Critical Sites of the Reentrant Circuit in Low-Voltage Areas

Introduction: The purpose of this study was to examine the reentrant circuit of ventricular tachycardias (VTs) involving the left anterior fascicle (LAF) in nonischemic cardiomyopathy.
Methods and Results: Six patients with nonischemic cardiomyopathy presented with VTs involving the LAF. Potentials in the diastolic or presystolic phase of the VT were identified close to the LAF in 3 patients and in the mid or inferior left ventricular (LV) septum in 3 patients. Superimposed on a CARTO or NavX 3-dimensional voltage map, the diastolic and presystolic potentials were recorded within or at the border of a low-voltage zone in the LV septum in all cases. In 2 patients, both left bundle fascicles participated in the reentrant circuit including a possible interfascicular VT in one case. Ablation targeting the diastolic or presystolic potentials near the LAF or in the midinferior LV septum eliminated the VTs in all patients with the occurrence of a left posterior fascicular block and the delayed occurrence of a complete atrioventricular block in each one patient. During the follow-up of 23 ± 20 months after ablation, 4 patients were free of ventricular tachyarrhythmias. Due to detoriation of heart failure, one patient died after 12 months and one patient underwent heart transplantation after 40 months.
Conclusions: Slow conduction in diseased myocardium close to the LAF or in the middle and inferior aspects of the LV septum may represent the diastolic pathway of VT involving the LAF.     

Mechanisms of Idiopathic Left Ventricular Tachycardia

Idiopathic Left Ventricular Tachycardia. Idiopathic left ventricular tachycardia (ILVT) differs from idiopathic right ventricular outflow tract (RVOT) tachycardia with respect to mechanism and pharmacologic sensitivity. ILVT can he categorized into three subgroups. The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of left posterior fascicle of the left bundle. This tachycardia is adenosine insensitive , demonstrates entrainment, and is thought to he due to reentry. The tachycardia is most often ablated in the region of the posteroinferior interventricular septum. A second type of ILVT is a form analogous to adenosine- sensitive RVOT tachycardia. This tachycardia appears to originate from deep within the interventricular septum and exits from the left side of the septum. This form of VT also responds to verapamil and is thought to he due to cAMP-mediated triggered activity. A third form of ILVT is propranolol sensitive. It is neither initiated or terminated by programmed stimulation, does not terminate with verapamil, and is transiently suppressed by adenosine, responses consistent with an automatic mechanism. Recognition of the heterogeneity of ILVT and its unique characteristics should facilitate appropriate diagnosis and therapy in this group of patients.