Idiopathic left ventricular tachycardia: new insights into electrophysiological characteristics and radiofrequency catheter ablation

Fascicular Ventricular Tachycardias: Potential Role of the Septal Fascicle

Ventricular tachycardias involving the fascicular system are amongst the most challenging and intriguing arrhythmias for cardiac electrophysiologists. Although some of the more common forms have been recognized clinically for decades, other variants continue to be characterized. Moreover, considerable uncertainty persists to date with regards to the mechanisms underpinning these arrhythmias. In this state-of-the-art review, we discuss the seminal historical and contemporary observations that have collectively advanced our understanding of fascicular ventricular tachycardias. From this base, we canvas the basic and clinical evidence supporting a potential role for the septal fascicular network and propose a new schema hypothesizing involvement of this fascicle. Although we focus primarily on the most common left posterior fascicular ventricular tachycardia, our discussion and proposal have mechanistic and therapeutic implications for the spectrum of fascicular arrhythmias.

Diagnosis and Management of Complex Reentrant Arrhythmias Involving the His-Purkinje System

The His-Purkinje system is a network of bundles and fibres comprised of specialised cells that allow for coordinated, synchronous activation of the ventricles. Although the histology and physiology of the His-Purkinje system have been studied for more than a century, its role in ventricular arrhythmias has recently been discovered with the ongoing elucidation of the mechanisms leading to both benign and life-threatening arrhythmias. Studies of Purkinje-cell electrophysiology show multiple mechanisms responsible for ventricular arrhythmias, including enhanced automaticity, triggered activity and reentry. The variation in functional properties of Purkinje cells in different areas of the His-Purkinje system underlie the propensity for reentry within Purkinje fibres in structurally normal and abnormal hearts. Catheter ablation is an effective therapy in nearly all forms of reentrant arrhythmias involving Purkinje tissue. However, identifying those at risk of developing fascicular arrhythmias is not yet possible. Future research is needed to understand the precise molecular and functional changes resulting in these arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Mapping and Ablation of Fascicular Tachycardias (Reentrant and Nonreentrant)

Fascicular ventricular tachycardia (FVT) usually involves the left fascicular system; namely the left posterior fascicle, anterior fascicle, and rarely the upper septal fascicle. It may also involve the right Purkinje arborization. This tachycardia can be seen in normal heart or in the setting of structural heart diseases. Monomorphic FVT can be reentrant or nonreentrant and verapamil-sensitive left FVT is the second most common type of idiopathic ventricular tachycardia (VT) after right ventricular outflow tract VT. This article focuses on the practical approach for both reentrant and nonreentrant FVT, explaining the mechanism, electrocardiographic features, and electrophysiologic features of FVT.

Idiopathic Left Ventricular Tachycardia Originating in the Left Posterior Fascicle

Ventricular tachycardias originating from the Purkinje system are the most common type of idiopathic left ventricular tachycardia. The majority if not all of the reentrant circuit involved in this type of tachycardia is formed by the Purkinje fibres of the left bundle branch, particularly the left posterior fascicle. In general, slowly conducting Purkinje fibres (P1) form the antegrade limb, and normally conducting Purkinje fibres (P2) form the retrograde limb of the reentrant circuit of the ventricular tachycardia originating from the left posterior fascicle. Elimination of the critical Purkinje elements in the reentrant circuit is the route to successful ablation. While the reentrant circuit identified by activation mapping provides the roadmap to ablation targets, comparing the difference in the His-ventricular interval during sinus rhythm and tachycardia also helps to identify the critical site in the reentrant circuit.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Long-term mode and timing of premature ventricular complex recurrence following successful catheter ablation

PURPOSE

Catheter ablation of premature ventricular contractions (PVCs) is highly successful and has become the hallmark treatment for symptomatic or highly prevalent cases. However, few studies exist that evaluate the outcomes of ablation and likely mechanisms of PVC recurrence beyond 1 year of follow-up.

METHODS

This study is a retrospective analysis of patients who underwent catheter ablation for symptomatic PVCs with acute procedural success and had clinical follow-up ≥ 12 months.

RESULTS

Forty-four patients (24 women; age 53.5 ± 4.8 years) following acutely successful PVC ablation with long-term follow-up were studied. At a mean of 36 ± 6 months, overall long-term ablation success was 75% (33/44 patients). Notably, recurrence of the targeted PVC focus was low (6.8%, 3/44 patients); the majority of recurrences were from a new source location (18.2%, 8/44 patients). The time course for targeted versus de novo PVC recurrences was significantly different: recurrence of a PVC similar to the targeted PVC morphology occurred at a mean of 5.0 ± 2.0 months, while recurrence of a PVC different from the index case occurred at a mean of 35.8 ± 17.1 months (p = 0.01). Non-ischemic cardiomyopathy was associated with increased risk of PVC recurrence (odds ratio [OR] 14.50 (95% confidence interval [CI] 1.92-109.33, p = 0.01)) and was a significant negative prognostic factor in multivariate analysis for PVC recurrence survival (hazard ratio [HR] 4.63, 95% CI 1.03-20.74, p = 0.04).

CONCLUSIONS

The majority of long-term PVC recurrences occur late in follow-up, at locations remote from the targeted PVC source or sources. Such sites may represent ongoing substrate evolution; additional work is required to determine the precise substrate alterations which promote such arrhythmogenic changes.

Spectrum of Fascicular Arrhythmias

Fascicular arrhythmias encompass a wide spectrum of ventricular arrhythmias that depend on the specialized conduction system of the right and left ventricles. These arrhythmias include premature ventricular complexes, monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, and ventricular fibrillation. These arrhythmias may be organized by mechanism, including intrafascicular reentry, interfascicular reentry, and focal. Mapping and ablation of the fascicular system can result in high cure rates of debilitating and potentially life-threatening arrhythmias. When approaching these arrhythmias, careful consideration of the structure of the His Purkinje system as well as their electrophysiologic properties may help guide even the most complex of arrhythmias.

Monomorphic and polymorphic ventricular tachycardias arising from the His–Purkinje system: what do we know?

Monomorphic and polymorphic Purkinje-related ventricular tachycardias (VTs) may occur in patients with and without underlying structural heart disease. Monomorphic Purkinje-related VTs can be divided into different entities: verapamil-sensitive left fascicular VTs; bundle branch reentry tachycardias (BBRT); interfascicular VTs and focal Purkinje VTs. The most frequent fascicular VT is left posterior fascicular VT, characterized by macro-reentry within the posterior Purkinje network. However, the reentry may also be located in the anterior Purkinje network (left anterior fascicular VT). BBRT is also a macro-reentry-tachycardia, utilizing both the right and the left bundle branch as the antegrade and the retrograde limb and is often associated with pre-existing conduction disturbances in the specific conduction system. Interfascicular VT is rare and characterized by a macro-reentry within the left fascicles. BBRT and interfascicular VT may also occur in the same patient. In contrast to the mentioned macro-reentry mechanisms there are focal Purkinje-related VTs arising from the anterior or posterior Purkinje system. Focal Purkinje triggered premature ventricular contractions originating from the distal Purkinje arborization in patients without a structural heart disease, as well as in patients with known ischemic heart disease or an underlying channelopathy such as Brugada syndrome may induce polymorphic VTs. Catheter ablation is an effective treatment option for both monomorphic as well as polymorphic Purkinje-related VTs, often resulting in noninducibility and freedom from VT recurrence. A systematic analysis of the surface ECG and the intracardiac electrograms is essential for successful ablation of these heterogeneous and potentially curable VTs.

Ventricular tachycardia without apparent heart disease: long-term follow-up

The purpose of the study was to evaluate the long-term prognosis of ventricular tachycardia (VT) in patients without structural heart disease (HD).

METHODS

Holter monitoring, exercise test, echocardiography, right angiography, coronary angiography, and electrophysiologic study were performed in 810 patients with VT.

RESULTS

Eighty patients (mean age, 45 ± 17 years) had no apparent HD. VT was reproduced at electrophysiologic study in 62 patients. Mean follow-up was 9.7 ± 7 years. Initially, 91% were treated with drugs. Defibrillator was implanted in 4, including 2 for arrhythmogenic right ventricular cardiomyopathy diagnosed later. VT ablation was performed in 3 patients. Three patients older than 70 years died of nonarrhythmic cause. Other patients are alive without antiarrhythmic drug treatment in 50%. Three developed a dilated cardiomyopathy; and 2, atrial fibrillation.

CONCLUSIONS

Invasive treatment was rarely required in patients with VT without HD. The prognosis was only dependent on the age and the pattern of electrocardiogram in VT.

The significance of repetitive ventricular responses induced by radiofrequency energy application for idiopathic left ventricular tachycardia

In radiofrequency (RF) ablation for idiopathic left ventricular tachycardia (ILVT), the termination of tachycardia during RF ablation is considered a hallmark of success. However, in cases of patients with difficulty of induction of ventricular tachycardia (VT), the evaluation of procedural success can be problematic. We have observed thermal responses reflected as ventricular rhythm change to RF energy delivered on sinus rhythm for ILVT. We therefore describe the significance of repetitive ventricular responses. The study subjects were 11 ILVT patients for whom RF energy was delivered during sinus rhythm because of difficulty in re-induction of tachycardia. During each energy delivery, we focused on the occurrence of repetitive ventricular responses especially exhibiting a similar morphology to clinical VT. The repetitive ventricular responses were noted in 10 of 11 patients. Two patients received a second procedure due to the recurrence of ILVT. The mean follow-up period was 36.2+/-12.8 months. The clinical course of the remaining patients was favorable and without recurrence of ILVT. Based on the favorable clinical outcomes, ablation-induced repetitive ventricular responses with similar QRS morphology to clinical ILVT are useful markers for selecting an ablation site and could be used as an additional mapping method, termed as "thermal mapping".

Idiopathic Ventricular Tachycardia: Diagnosis and Management

Idiopathic ventricular tachycardia (VT) is an uncommon form of VT that is seen in patients without structural heart disease. It is commonly seen in young patients and usually has a benign course. Recent studies have delineated the mechanisms and anatomical locations of this form of VT. Recognition of various forms of idiopathic VT based on characteristic QRS morphology from the 12-lead electrocardiogram (ECG) has important prognostic and therapeutic implications. The understanding of the mechanisms of idiopathic VT has led to the use of specific antiarrhythmic drugs targeting particular arrhythmias. Recent technological advances in the field of mapping and catheter ablation have led to a suitable alternative to drug therapy with a very high cure rate. This review describes the clinical features, ECG recognition, and management of idiopathic monomorphic VT.

Idiopathic fascicular left ventricular tachycardia: Linear ablation lesion strategy for noninducible or nonsustained tachycardia

BACKGROUND

Idiopathic "fascicular" left ventricular tachycardia (IFLVT) is frequently not inducible or nonsustained at the time of planned catheter ablation. The mechanism of the arrhythmia has been suggested to be reentry involving a sizable area of the LV inferior septum extending from base toward the apex.

OBJECTIVE

We tested the ability of a series of radiofrequency lesions delivered in a linear fashion to the inferior-mid septum to control ventricular tachycardia not amenable to standard mapping ablation strategies.

METHODS

Programmed stimulation both at baseline state and with isoproterenol after heart rate was increased by at least 25% was performed in all patients. The patients included in the study were either non-inducible or only had brief nonsustained VT not amenable to "traditional" mapping. A detailed electroanatomic map of the LV was performed in sinus rhythm. The location of the linear lesion along the inferior septum was guided by the presence of Purkinje potentials, with pacemapping as an additional guide. A linear lesion was placed perpendicular to the long axis of the ventricle approximately midway from the base to the apex in the region of the mid to mid-inferior septum. Radiofrequency lesions were delivered using a 4mm tip catheter at 50 Watts and 52 degrees for 60-90 seconds.

RESULTS

Of 122 consecutive patients who underwent ablation of idiopathic VT from 1999 to 2003, 15 had IFLVT based on standard diagnostic criteria. Six of the 15 patients (40%) had nonsustained or no inducible VT in the EP lab. The number of RF lesions ranged from 7 to 15 (mean 9). The length of the effective linear lesion ranged from 1.2 to 2.2 cm (mean 1.7 cm). Development of left posterior fascicular block was noted in two of the six patients. However, despite the absence of development of left posterior fascicular block in the other four patients, no VT or premature ventricular beats could be induced after ablation using the same provocation maneuvers as performed in the baseline state. No spontaneous arrhythmias occurred during follow-up to 16 +/- 8 months (range 6 to 30 months).

CONCLUSION

In patients with difficult to induce or nonsustained VT with the typical right bundle branch block pattern and a superiorly directed axis on 12-lead ECG, RF energy ablation delivered in a linear fashion approximately midway to two thirds toward the apex along the mid to inferior septum and perpendicular to the plane of the septum is safe and effective for VT control.

Unusual Features of an Idiopathic Ventricular Tachycardia Arising from the Left Ventricular Outflow Tract

We encountered a 40-year-old man with recurrent symptomatic palpitations manifested as monomorphic ventricular tachycardia (VT) of a right bundle branch block (RBBB) pattern with an inferior frontal axis. Physical examination, chest roentgenogram, and echocardiogram were unremarkable. The VT could be provoked by treadmill exercise testing. Electrophysiologic study revealed that the VT could be reproducibly initiated with either atrial or ventricular pacing at cycle lengths between 500 and 400 ms. With overdrive ventricular pacing, the VT could be terminated. Of note was the observation that intravenous adenosine was not effective, but intravenous verapamil could interrupt the VT. The VT was pace mapped to be arising from a site at the left ventricular outlet tract (LVOT). Notably, during pace mapping, the pacing spike was immediately followed by the beginning of the paced QRS complex, and during VT, there was no time delay between the earliest local activation and the onset of QRS complex. Furthermore, there was no mid-diastolic activity or Purkinje potential that could be recorded during sinus rhythm and VT. Subsequently, the VT was successfully ablated with radiofrequency energy as guided by pace mapping. In summary, an idiopathic VT arising from the LVOT was found to be cycle lengths- and catecholamine-dependent, adenosine-insensitive but verapamil responsive. These unusual features suggest that either microreentry or triggered activity could be the underlying mechanism.

Myocardial Bundles with Slow Conduction Properties are Present on the Left Interventricular Septal Surface of Normal Human Hearts

INTRODUCTION

The aim of this study was to examine the electrophysiologic characteristics of the normal left interventricular septum (LIVS).

METHODS AND RESULTS

We explored the LIVS in search of endocardial potentials following ventricular electrograms during sinus rhythm in 28 patients without structural heart disease. In all patients, low-frequency (mean amplitude: 0.81 +/- 0.33 mV) systolic potentials (LA1) were detected in a basal-to-apical activation sequence (earliest to latest QRS-LA1 interval: 93.3 +/- 10.8 ms to 127.1 +/- 16.6 ms). Programmed stimulation demonstrated decremental conduction properties, and the effective refractory period of the tissue between the ventricular electrogram and LA1 at baseline (376.7 +/- 48.8 ms) was significantly prolonged by disopyramide (421.3 +/- 54.1 ms, P < 0.05 vs baseline). In 21 patients (75%), diastolic potentials (LA2) morphologically similar to LA1 (mean amplitude: 0.52 +/- 0.17 mV) were detected in an apical-to-basal activation sequence (earliest to latest QRS-LA2 interval: 368.9 +/- 32.4 ms to 440.7 +/- 45.8 ms). Para-Hisian pacing with capture of the His bundle showed shorter S-LA1 and S-LA2 intervals compared to the beats without His-bundle capture but with ventricular capture (156.3 +/- 11.2 ms vs 183.2 +/- 12.3 ms, and 385.7 +/- 21.6 ms vs 397.4 +/- 23.4 ms, respectively, P < 0.0001). At the same rate, the LA1-LA2 interval was significantly shorter during right ventricular apical than atrial overdrive pacing (220.4 +/- 23.1 ms vs 261.4 +/- 30.7 ms, P < 0.0001).

CONCLUSION

Unique myocardial bundles with slow conduction properties and various electrical connections with the specialized conduction system may exist in the LIVS of normal human hearts.

Adenosine-sensitive wide-complex tachycardia: an uncommon variant of idiopathic fascicular ventricular tachycardia--a case report

Most wide-complex tachycardias encountered in the emergency department (ED) are ventricular in origin, most commonly associated with structural heart disease. Ventricular tachyarrhythmias range in severity from life-threatening rhythms (eg, ventricular fibrillation and hemodynamically compromising ventricular tachycardia [VT]) to idiopathic forms of VT, which have a benign clinical course and a more favorable prognosis. The authors present the case of a 34-year-old woman who presented to the ED, with a wide-complex tachycardia with a right-bundle-branch block (RBBB) morphology and a right inferior axis, which was terminated with adenosine. The patient was previously misdiagnosed as suffering from a paroxysmal supraventricular tachycardia (SVT), which was unresponsive to beta-blocker therapy. Although the tachycardia responded to adenosine, suggestive of an SVT, the patient was referred to the arrhythmia service, where further work-up revealed an uncommon form of an idiopathic VT, originating from the left anterior fascicle. The authors discuss the unique electrocardiographic and electrophysiologic properties and useful diagnostic maneuvers required to properly identify this form of VT.

Electroanatomic substrate of idiopathic left ventricular tachycardia: unidirectional block and macroreentry within the purkinje network

BACKGROUND

An abnormal potential (retroPP) from the left posterior Purkinje network has been demonstrated during sinus rhythm (SR) in some patients with idiopathic left ventricular tachycardia (ILVT). We hypothesized that this potential can specifically be identified and be a critical substrate for ILVT.

METHODS AND RESULTS

In 9 patients with ILVT and 6 control patients who underwent mapping of the left ventricle during SR using 3-dimensional electroanatomic mapping, an area with retroPP was found within the posterior Purkinje fiber network only in patients with ILVT. The earliest and latest retroPP was 185.4+/-57.4 and 465.2+/-37.3 ms after Purkinje potential; in the other patient with ILVT, an entire left ventricle mapping demonstrated a slow conduction area and passive retrograde activation along the posterior fascicle during ILVT. ILVT was noninducible in 3 patients after SR mapping. Diastolic potentials critical for ILVT during ILVT coincided with the earliest retroPP during SR in 7 patients. Mechanical termination of ILVT occurred in 5 patients. A single radiofrequency pulse was applied at the site with mechanical translation in 5 patients and the site with diastolic potential in 2 patients, and 3 radiofrequency pulses were delivered to the site with the earliest retroPP in the other 3 patients without inducible ILVT after SR mapping. No ILVT was inducible during control stimulation, and none recurred during follow-up of 9.1+/-5.1 months.

CONCLUSION

In patients with ILVT, abnormal retroPP within the posterior Purkinje fiber network is a common finding. The earliest retroPP critical for ILVT substrate can be used for guiding successful ablation.

Mapping and ablation of ventricular tachycardia in children and adolescents

Ventricular tachycardia is a rare arrhythmia in the pediatric population that occurs in structurally normal and abnormal hearts. The treatment of ventricular tachycardia is aimed at reducing symptoms and the risk of sudden death. The intracardiac electrophysiology study and radiofrequency ablation have come to the forefront of diagnostic and therapeutic options for patients with ventricular arrhythmias. The indications for radiofrequency ablation are debated, but it has been shown to be an effective and safe means of eliminating ventricular tachycardia. The purpose of this review is to outline the mechanisms and electrophysiologic characteristics of ventricular tachycardia, discuss the forms common to the pediatric population and summarize the indications, success and complications of radiofrequency ablation for ventricular tachycardia.

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 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.

Effects of verapamil and lidocaine on two components of the re-entry circuit of verapamil-senstitive idiopathic left ventricular tachycardia

OBJECTIVES

We characterized pharmacologically the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) with regard to the late diastolic potential (LDP).

BACKGROUND

We showed that the slow conduction zone of ILVT could be divided into two components by LDP; that is, the distal component with a tachycardia-dependent conduction delay property and the proximal one without it.

METHODS

Electrophysiologic studies were performed in eight consecutive patients. The LDP was recorded during left ventricular (LV) mapping during ILVT. Entrainment was performed from the right ventricular outflow tract while recording LDP. The effects of lidocaine (1 mg/kg body weight) and verapamil (0.5 or 1.0 mg) were examined during entrainment.

RESULTS

The LDPs preceding the Purkinje potential (PP) were serially recorded from the upper third to the middle of the LV septum along the narrow longitudinal line. The ventricular tachycardia (VT) cycle length increased after lidocaine (p < 0.05), and further after verapamil (p < 0.05). The increments in the VT cycle length after administration of the drugs strongly correlated with those in LDP-PP (r > 0.9 for both drugs). The interval from the ventricular potential to LDP was unchanged after administration of the drugs. In one patient, verapamil terminated VT by local conduction block between LDP and PP. The LDP-PP measured during entrainment increased after lidocaine, and further after verapamil, whereas the interval from the stimulus to LDP remained unchanged.

CONCLUSIONS

The component distal to LDP is mainly calcium channel-dependent and partly depressed sodium channel-dependent. The proximal component is considered to be sodium channel-dependent (normal).

Radiofrequency ablation of idiopathic left ventricular tachycardia at the site of earliest activation as determined by noncontact mapping

INTRODUCTION

The most effective method for guiding radiofrequency (RF) ablation of idiopathic left ventricular tachycardia (ILVT) has yet to be determined. We investigated the use of noncontact mapping in five patients with this condition.

METHODS AND RESULTS

The multielectrode array was positioned in the left ventricular apex via the retrograde approach. Isopotential color maps of ILVT were examined to determine the site of earliest endocardial activation. The ablation catheter was steered to the target site using the locator signal. Pace mapping was performed and contact electrograms examined for diastolic potentials. RF energy was applied to the target site. Sustained ventricular tachycardia was induced in 2 patients and nonsustained ventricular tachycardia in 3. The site of earliest activation was at the apical septum in 3, the inferior apex in 1, and the base of the inferior wall in 1. Mean timing was 21 +/- 10 msec before onset of the surface QRS. Diastolic activity was visualized with noncontact mapping at the base of the septum in 1 patient. A Purkinje potential was seen at the ablation site in only 1 patient. No diastolic activity was seen in the remaining 3 patients. Tachycardia was successfully terminated in all 5 patients with a median of four RF applications. No patient suffered a recurrence after 9.6 +/- 4.7 months of follow-up.

CONCLUSION

By identifying the precise site of earliest activation during ILVT, noncontact mapping has been shown to be an effective and safe method for guiding RF ablation.

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.

Structure of the reentrant circuit of idiopathic left ventricular tachycardia: new insights into the role of the Purkinje network

In idiopathic left ventricular tachycardia (ILVT), the reentrant circuit is considered to involve the Purkinje system, and the Purkinje potential (P-potential) appears to be a marker for successful ablation. However, the characteristics of the reentrant circuit in ILVT have not yet been defined. In 2 cases of ILVT, we performed detailed mapping along the left ventricular septum during VT and sinus rhythm. ILVTs were successfully ablated at the posteroapical area of the left ventricular septum where the high frequency P-potential was recorded and this portion was considered to be the exit site of the reentrant circuit. A small P-potential was also recorded at the portion proximal to the exit site, and it preceded the P-potential at the exit site. However, the local ventricular electrogram at the exit site preceded that at the proximal site during VT. Moreover, the small P-potential was orthodromically entrained by ventricular pacing from the proximal site. These findings suggest that the reentry circuit of ILVT appeared to have considerable size.

Diastolic potentials observed in idiopathic left ventricular tachycardia

Radiofrequency catheter ablation (RF-CA) has demonstrated a high success rate in eliminating idiopathic left ventricular tachycardia (ILVT), and the target site is determined by the score of pace mapping or the Purkinje potential (PP) preceding the onset of the ventricular activation, which is considered to indicate the exit site of the reentrant circuit. However, only a few reports have described the potential obtained from the slow conduction zone. RF-CA was successfully performed in 8 patients with ILVT. Careful mapping of the left ventricle during tachycardia was carried out to find the diastolic potential (DP). A DP was obtained in 4 patients (group 1), but not in 4 others (group 2). The local electrogram was recorded from the distal tip of the ablation catheter during the RF current application in order to investigate the pattern of termination of ILVT. A DP was recorded at the point where the catheter was slightly pulled back to a site proximal to the exit site of the reentrant circuit at the left interventricular basal septum. In group 1, conduction block between the DP and PP eliminated ILVT in 3 out of 4 cases, and 1 case showed conduction block between the DP and ventricular potential. In 2 out of 4 patients in group 2, the local electrogram showed conduction block between PP and the ventricular potential when VT terminated. The ablation site in group 1 was located relatively more basal than that in group 2 in anatomy. A DP was obtained in a half of the cases with ILVT and RF-CA at this site could eliminate ILVT. A DP was obtained at a site relatively basal to the exit of the reentrant circuit and it is considered that this is a useful marker in terms of the successful ablation of ILVT.

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.