Negative Participation of the Left Posterior Fascicle in the Reentry Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia

Septal fascicle involvement during a Purkinje-related ventricular tachycardia: Electroanatomic correlation using omnipolar technology

Idiopathic verapamil-sensitive fascicular ventricular tachycardia (VT) is the most common form of Purkinje-related ventricular tachycardia (PRVT). Left septal fascicle (LSF) involvement and its connections with the other fascicles, have been recently reported as a pathophysiologic mechanism for this form of PRVT. We describe a case of idiopathic PRVT with LSF involvement using omnipolar technology (OT) mapping in relation to a false tendon. Ablation in the area with concealed fusion entrainment did not terminate the tachycardia. However, radiofrequency application in the area of LSF with manifest fusion entrainment, resulted in immediate tachycardia termination. Six months follow-up showed no tachycardia recurrence.

Efficacy of High-Density Three-Dimensional Mapping for Verapamil-Sensitive Left Posterior Fascicular Ventricular Tachycardia in Pediatric Patients

In verapamil-sensitive left posterior fascicular ventricular tachycardia (LPF-VT), radiofrequency catheter ablation (RFA) is performed targeting mid-to-late diastolic potential (P1) and presystolic potential (P2) during tachycardia. This study included four patients who had undergone electrophysiological study (EPS) and pediatric patients with verapamil-sensitive LPF-VT who had undergone RFA using high-density three-dimensional (3D) mapping. The included patients were 11-14 years old. During EPS, right bundle branch block and superior configuration VT were induced in all patients. VT mapping was performed via the transseptal approach. P1 and P2 during VT were recorded in three of the four patients. All patients initially underwent RFA via the transseptal approach. In three patients, P1 during VT was targeted, and VT was terminated. The lesion size indices in which VT was terminated were 4.6, 4.6, and 4.7. For one patient whose P1 could not be recorded, linear ablation was performed perpendicularly in the area where P2 was recorded during VT. Among the three patients in whom VT was terminated, linear ablation was performed in two to eliminate the ventricular echo beats. In all patients, VT became uninducible in the acute phase and had not recurred 8-24 months after RFA. High-density 3D mapping with an HD Grid Mapping Catheter allows recording of P1 and P2 during VT and may improve the success rate of RFA in pediatric patients with verapamil-sensitive LPF-VT.

Purkinje-Related Ventricular Tachycardia and Ventricular Fibrillation: Solved and Unsolved Questions

Of the monomorphic ventricular tachycardias, there are 4 specific tachycardias related to the Purkinje system: 1) idiopathic verapamil-sensitive fascicular ventricular tachycardia (FVT); 2) non-re-entrant FVT; 3) bundle branch re-entry and interfascicular re-entry; and 4) Purkinje-mediated VT in structural heart disease. Verapamil-sensitive FVT is classified into 4 types according to the location of the circuit: 1) left posterior type; 2) left anterior type; 3) left upper septal type;and 4) reverse type. And, in the left anterior and posterior types, there are septal and papillary muscle subtypes. Although macro-re-entry has been reported to be the mechanism underlying verapamil-sensitive FVT, recording the entire circuit is challenging. One possible reason is that the Purkinje-muscle junction may penetrate the myocardial layer as a part of the circuit. The Purkinje network may thus play an important role in the initiation and maintenance of ventricular fibrillation. Further, it has been reported that the development and the abnormalities of the Purkinje system are associated with the arrhythmogenesis of ventricular fibrillation. Furthermore, it has been reported that catheter ablation of trigger ventricular premature complexes, and/or "de-networking" of the Purkinje system, can be used as electrical bailout therapy. There is a hypothesis that the intramural Purkinje system is involved in the generation of J waves. Nevertheless, as there are still unresolved issues that must be debated and accurately analyzed, this review aims to discuss the solved and unsolved questions related to Purkinje-related arrhythmias.

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.

A single premature stimulation from the para-Hisian region unmasked negative involvement of the left anterior fascicle in the verapamil-sensitive ventricular tachycardia with a right bundle branch block and right-axis deviation

A 33-year-old man had verapamil-sensitive ventricular tachycardia (VT) with a right bundle branch block (RBBB) and right axis deviation. Programmed stimulation from the para-Hisian region induced ventricular tachycardias (VT1 or VT2). VT1 was entrained during pacing from the para-Hisian region. A single para-Hisian stimulation antidromically captured the proximal portion of the left anterior fascicle (LAF), but the cycle length of VT2 remained unchanged. This observation indicated that the upper limb of the LAF was a bystander of the reentry circuit. We have clarified this mechanism with applying a single premature stimulation from the para-Hisian region.

Reverse-Type Left Posterior Fascicular Ventricular Tachycardia: A New Electrocardiographic Entity

OBJECTIVES

This study sought to demonstrate a new type of verapamil-sensitive fascicular ventricular tachycardia (VT) with a reverse circuit.

BACKGROUND

Left posterior fascicular ventricular tachycardia (LPFVT) is the most common form of verapamil-sensitive fascicular VT. Reverse-type LPFVT has not been reported.

METHODS

We searched for a reverse-type LPFVT among 242 patients with verapamil-sensitive VT from February 2006 to September 2019.

RESULTS

Three patients had a reverse-type LPFVT (cycle lengths: 340, 360, and 340 ms). QRS configuration during VT was narrow (140, 150, and 140 ms) and exhibited rSr' morphology in V₁ with an early precordial transition and inferior axis. Two of 3 patients had common-type LPFVT. During reverse-type LPFVT, the earliest ventricular activation was the left superior middle septum. Fragmented Purkinje potentials (P1) buried within the local ventricular electrogram were recorded with an activation sequence from the apex to the base and were linked to the subsequent left ventricular septal activation. After radiofrequency catheter ablation at P1 during LPFVT, the reverse-type LPFVT also became noninducible. In 1 patient with only the reverse-type LPFVT, radiofrequency catheter ablation at the earliest LV activation site suppressed VT. These findings suggest that this new type of verapamil-sensitive fascicular VT shares a re-entrant circuit with a reverse direction of common LPFVT with an intramural exit site at the superior middle septum.

CONCLUSIONS

Reverse-type LPFVT can occur. If common LPFVT exists, diastolic P1 during LPFVT can be a common target of ablation. If only reverse-LPFVT is inducible, the earliest ventricular activation site can be a target.

Left posterior fascicular ventricular tachycardia in a young infant with a structurally normal heart: Clinical course and caveats to electrocardiographic diagnosis

In this illustrative case report, we describe a rare case of left posterior fascicular ventricular tachycardia (LPFVT) in a 2 month-old infant with emphasis on electrocardiographic caveats to diagnosis. The clinical course, treatment, and eventual resolution of the VT over a 2 year follow-up is comprehensively compared and contrasted to a modicum of individual such case reports of infants. The corpus of each such case of infantile LPVT is systematically reviewed and succinctly summarized in a tabular compendium. The collective knowledge compiled here should allow for a refined approach to diagnosis and management of this unusual arrhythmia.

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.

New Insights on Verapamil-Sensitive Idiopathic Left Fascicular Tachycardia

Verapamil-sensitive left fascicular monomorphic ventricular tachycardia (LF-VT) was first described ~4 decades ago. Our knowledge regarding this arrhythmia is evolving continuously. The current review aims to highlight up to date aspects of this arrhythmia focusing on its ECG recognition, new considerations of the reentrant circuit, ablation targets in inducible and non-inducible patients and the approach to LF-VT with multiform morphology.

Peculiar Electrocardiographic Aspects of Wide QRS Complex Tachycardia: When Differential Diagnosis Is Difficult

Wide complex tachycardia may represent a challenge for correct interpretation of standard electrocardiogram, which is crucial for proper patient management. For this reason, algorithms based on electrocardiographic criteria have been developed to guide interpretation in a step-by-step approach. Despite their greater accuracy, some cases of wide QRS complex tachycardia are a challenge. Some peculiar forms of ventricular tachycardia, and complex supraventricular substrate or particular clinical condition, may originate a challenging electrocardiographic pattern. In this article, a series of peculiar cases of wide QRS complex tachycardia is presented as paradigm of how important a comprehensive clinical approach is in these patients.

Catheter Ablation of Ventricular Tachycardia in Structurally Normal Hearts: Indications, Strategies, and Outcomes-Part I

Catheter ablation of ventricular tachycardia (VT) is being increasingly performed; yet, there is often confusion regarding indications, outcomes, and how to identify those patient populations most likely to benefit. The management strategy differs between those with structural heart disease and those without. For the former, an implantable cardioverter-defibrillator (ICD) is typically required due to an elevated risk for sudden cardiac death, and catheter ablation can be used as adjunctive therapy to treat or prevent repetitive ICD therapies. In contrast, VT or premature ventricular contractions in the setting of a structurally normal heart carries a low risk for sudden cardiac death; accordingly, there is typically no indication for an ICD. In these patients, catheter ablation is considered for symptom management or to treat tachycardiomyopathy and is potentially curative. Here, the authors discuss the pathophysiology, mechanism, and management of VT that occurs in the setting of a structurally normal heart and the role of catheter ablation.

Macroreentrant Loop in Ventricular Tachycardia From the Left Posterior Fascicle

Background—

The underlying mechanisms of reentry during left posterior fascicular ventricular tachycardia (LPF-VT) remain unclear. The purpose of this study is to describe the components of LPF-VT reentry circuit and their electrophysiological properties.

Methods and Results—

Fourteen consecutive patients with LPF-VT underwent electrophysiology study and radiofrequency ablation. Via a multipolar electrode catheter placed from a retrograde aortic approach, a sharp inflection, high-frequency potential (P1) was detected in 9 patients (64%). The ranges of length and velocity of recorded P1 were 9 to 30 mm and 0.5 to 1.2 mm/ms, respectively. Macroreentry involving the ventricular myocardium was confirmed to be the mechanism in all patients by premature ventricular stimuli delivery or entrainment of LPF-VT with progressive fusion, or both. During LPF-VT, the earliest left posterior fascicle (LPF, P2) was considered to be the site of connection between P1 and P2, and the site of the earliest P2 along the left posterior ventricular septum correlated well with the His-ventricular interval during tachycardia. Radiofrequency ablation focused on the P1 potentials (9 patients with a recorded P1) or earliest P2 (5 patients without a recorded P1) was successful in all 14 patients. After 4.5±3.0 months of follow-up, no patients had recurrence of LPF-VT.

Conclusions—

The LPF-VT macroreentrant loop involves the ventricular myocardium, a part of the LPF, a slow conduction zone, and in certain cases, a specially conducting P1 fiber. The His-ventricular interval during LPF-VT correlates with multiple electrophysiological measures and is a useful marker for identification of the optimal ablation site.

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.

Catheter Ablation of Fascicular Ventricular Tachycardia: Long-Term Clinical Outcomes and Mechanisms of Recurrence

Supplemental Digital Content is available in the text.

Fascicular ventricular tachycardia (FVT) is a common form of sustained idiopathic left ventricular tachycardia with an Asian preponderance. This study aimed to prospectively investigate long-term clinical outcomes of patients undergoing ablation of FVT and identify predictors of arrhythmia recurrence.

Insights into the mechanism of idiopathic left ventricular tachycardia: a case report and literature review

Left ventricular posterior fascicular tachycardia (LVPFT) is an idiopathic form of VT characterized by right bundle branch block morphology and left axis deviation. The mechanism of LPFVT is thought to be localized reentry close to the posterior fascicle. We present the case of a 24-year-old medical student who was admitted to the emergency department complaining of palpitations. The ECG showed an aspect suggestive of LVPFT. Vagal maneuvers, adenosine and i.v. Metoprolol were ineffective in terminating the arrhythmia. Conversion to sinus rhythm was obtained 10 h later, with i.v Amiodarone. The ECG in sinus rhythm showed left posterior fascicular block. Because antiarrhythmic drugs were not desired by the patient, VT ablation was proposed. The electrophysiological study identified the mechanism of arrhythmia to be reentry using the slowly conducting verapamil-sensitive fibers as the antegrade limb and the posterior fascicle as the retrograde limb. Radiofrequency applications near the posterior fascicle, in the lower half of the interventricular septum, at the junction of the two proximal thirds with the distal third interrupted the tachycardia and made it non-inducible at programmed stimulation. The case is unusual as the patient had a left posterior fascicular block during sinus rhythm before ablation. This demonstrates that the reentry circuit of VT does not need antegrade conduction through the posterior fascicle for perpetuation.

Demonstration of posterior fascicle to myocardial conduction block during ablation of idiopathic left ventricular tachycardia: an electrophysiological predictor of long-term success

BACKGROUND

Idiopathic left ventricular tachycardia (ILVT) is a common form of ventricular tachycardia (VT) in structurally normal heart. Different methods have been proposed for radiofrequency ablation (RFA) of ILVT that have good short-term results but recurrence is higher. Termination of tachycardia during RFA and/or noninduciblity has been the procedural end point.

OBJECTIVE

To describe electrophysiological markers that add to long-term freedom from recurrences.

METHODS

Fifteen patients with ILVT underwent RFA guided by 3-dimensional electroanatomical mapping. After creating a 3-dimensional geometry of the left ventricle (LV), the conduction system of the LV was mapped by tracing from His recording from the left ventricular outflow tract and distally till the fascicles and perifascicular myocardium. VT was induced by using programmed electrical stimulation. Ablation was done targeting the distal posterior fascicle and extended linearly to the surrounding myocardium till conduction block was achieved between the fascicle-Purkinje network and the left ventricular myocardium.

RESULTS

All patients (13 men; mean age 32 ± 9 years) had inducible VTs. The mean tachycardia cycle length was 320 ± 28 ms. Radiofrequency energy was given to the distal posterior fascicle and the myocardium, with an aim to achieve a myocardial-fascicular conduction block in addition to the termination of VT and noninducibility. Ablation was successful in all. No recurrence of tachycardia was seen in any patient on follow-up (20.8 ± 8.5 months).

CONCLUSIONS

Distal posterior fascicle and Purkinje-myocardial junction is an effective target site for ILVT ablation. The demonstration of myocardial to fascicle conduction block serves as an important electrophysiological marker of successful ablation and improved long-term success.