Fascicular Ventricular Arrhythmias

Mapping and Ablation of Premature Ventricular Complexes: State of the Art

Premature ventricular complexes (PVCs) are common arrhythmias in clinical practice. Although benign and asymptomatic in most cases, PVCs may result in disabling symptoms, left ventricular systolic dysfunction, or PVC-induced ventricular fibrillation. Catheter ablation has emerged as a first-line therapy in such cases, with high rates of efficacy and low risk of complications. Significant progress in mapping and ablation technology has been made in the past 2 decades, along with the development of a growing body of knowledge and accumulated experience regarding PVC sites of origin, anatomical relationships, electrocardiographic characterization, and mapping/ablation strategies. This paper provides an overview of the main indications for catheter ablation of PVCs, electrocardiographic features, PVC mapping techniques, and contemporary ablation approaches. The authors also review the most common sites of PVC origin and the main considerations and challenges with ablation in each location.

Mapping of Purkinje-related ventricular arrhythmias by a multispline catheter with small and close-paired electrodes: Comparison with conventional catheters

BACKGROUND

Precise mapping of the Purkinje fiber network is essential in catheter ablation of Purkinje-related ventricular arrhythmias (PrVAs). We sought to evaluate the mapping ability of a multi-spline duodecapolar catheter (PentaRay) for PrVAs.

METHODS

Mappings of Purkinje fibers by PentaRay catheters were compared with those by conventional mapping catheters in consecutive patients undergoing catheter ablation of PrVAs from 2015 to 2022.

RESULTS

Sixteen PrVAs (7 premature ventricular contractions or non-reentrant fascicular tachycardias [PVCs/NRFTs] and 9 fascicular ventricular tachycardias [FVTs]) were retrospectively studied. In PVCs/NRFTs, earliest preceding Purkinje potentials (PPs) could be recorded by the PentaRay catheters but not by the mapping and ablation catheters in 5 cases. At the earliest PP sites, the precedence from the QRS onset was greater, and the amplitude of the preceding potentials was higher in the PentaRay catheter compared with those in the mapping and ablation catheter (-62.0 ± 42.8 vs. -29.4 ± 34.2 ms, P = 0.02; 0.45 ± 0.43 vs. 0.09 ± 0.08 mV, P = 0.02). In FVTs, late diastolic potentials (P1) were recorded by the PentaRay catheters but not by the mapping and ablation catheters or the linear duodecapolar catheter in 2 cases. The amplitude of P1 was higher in the PentaRay catheter compared with that in the linear duodecapolar catheter and the mapping and ablation catheters (0.72 ± 0.49 vs. 0.17 ± 0.18 vs. 0.27 ± 0.21 mV, P = 0.0006, P = 0.002). The localized critical PPs, defined as the earliest preceding potentials in PVCs/NRFTs and P1 in FVTs, could be recorded in all the patients by the PentaRay catheter. The mapping ability of critical PPs of PrVAs was better with the PentaRay catheter than with the conventional mapping catheters (16/16 vs. 9/16, P = 0.004 by McNemar exact test).

CONCLUSIONS

The PentaRay catheter has clinical advantages in mapping of the Purkinje fiber network to reveal critical PPs as ablation targets of PrVAs.

[Long-term results of catheter ablation of idiopathic and structural ventricular tachycardia]

Catheter ablation of ventricular tachycardia (VTs) has emerged as an effective treatment modality. Ablation procedures for idiopathic VTs depends on the anatomical origin of the arrhythmias, is highly effective in certain cases, and has been implemented as a first-line therapy in recent European guidelines. In contrast, catheter ablation of VTs in patients with structural heart disease has a significant risk of arrhythmia recurrence. Interventional treatment for patients with ischemic cardiomyopathy was studied in multiple randomized multicenter trials and it was shown that catheter ablation was more effective in arrhythmia suppression compared to conservative treatment modalities. Catheter ablation of nonischemic cardiomyopathy suffers from far higher rates of arrhythmia recurrences as documented in several long-term studies and often needs complex procedures with or without epicardial mapping and ablation. There is still no clear proof of a mortality benefit from catheter ablation of VTs in patients with or without structural heart disease. Nevertheless, recent guidelines recommend catheter ablation as an alternative to implantation of cardioverter-defibrillators (ICD) in selected cases.

Immunologic changes are detectable in the peripheral blood transcriptome of clinically asymptomatic Chagas cardiomyopathy patients

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a neglected parasitic disease that affects approximately 6 million individuals worldwide. Of those infected, 20-30% will go on to develop chronic Chagas cardiomyopathy (CCC), and ultimately many of these individuals will progress to advanced heart failure. The mechanism by which this progression occurs is poorly understood, as few studies have focused on early CCC. In this study, we sought to understand the physiologic changes associated with T. cruzi infection and the development of CCC. We analyzed gene expression in the peripheral blood of asymptomatic Chagas patients with early structural heart disease, Chagas patients without any signs or symptoms of disease, and Chagas-negative patients with and without early structural heart disease. Our analysis shows that early CCC was associated with a downregulation of various peripheral immune response genes, with gene expression changes suggestive of reduced antigen presentation and T cell activation. Notably, these genes and processes were distinct from those of early cardiomyopathy in Chagas-negative patients, suggesting that the processes mediating CCC may be unique from those mediating progression to other cardiomyopathies. This work highlights the importance of the immune response in early CCC, providing insight into the early pathogenesis of this disease. The changes we have identified may serve as biomarkers of progression and could inform strategies for the treatment of CCC in its early stages, before significant cardiac damage has occurred.

Diagnosis and management of ventricular tachycardia

Ventricular tachycardia (VT) describes rapid heart rhythms originating from the ventricles. Accurate diagnosis of VT is important to allow prompt referral to specialist services for ongoing management. The diagnosis of VT is usually made based on electrocardiographic data, most commonly 12-lead echocardiography (ECG), as well as supportive cardiac telemetric monitoring. Distinguishing between VT and supraventricular arrhythmias on ECG can be difficult. However, the VT diagnosis frequently needs to be made rapidly in the acute setting. In this review, we discuss the definition of VT, review features of wide-complex tachycardia (WCT) on ECG that might be helpful in diagnosing VT, discuss the different substrates in which VT can occur and offer brief comments on management considerations for patients found to have VT.

Anatomy and Pathology of the Cardiac Conduction System

The cardiac conduction system is formed of histologically and electrophysiologically distinct specialized tissues uniquely located in the human heart. Understanding the anatomy and pathology of the cardiac conduction system is imperative to an interventional electrophysiologist to perform safe ablation and device therapy for the management of cardiac arrhythmias and heart failure. The current review summarizes the normal and developmental anatomy of the cardiac conduction system, its variation in the normal heart and congenital anomalies, and its pathology and discusses important clinical pearls for the proceduralist.

Palpitations in a Young Woman With Breast Cancer

This case report describes a woman in her 20s who had a 1-day history of palpitations and dyspnea. Her medical history was significant for breast cancer.

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.

Idiopathic Ventricular Tachycardia

Idiopathic ventricular tachycardia (VT) is an important cause of morbidity and less commonly, mortality in patients with structurally normal hearts. Appropriate diagnosis and management are predicated on an understanding of the mechanism, relevant cardiac anatomy, and associated ECG signatures. Catheter ablation is a viable strategy to adequately treat and potentially provide a cure in patients that are intolerant to medications or when these are ineffective. In this review, we discuss special approaches and considerations for effective and safe ablation of VT arising from the right ventricular outflow tract, left ventricular outflow tract, left ventricular fascicles, papillary muscles, and moderator band.

Electrophysiological characteristics and long-term outcome of substrate-based catheter ablation for left posterior fascicular ventricular tachycardia targeting fragmented antegrade Purkinje potentials during sinus rhythm

AIMS

The aim of this study was to investigate the electrophysiological characteristics and long-term outcome of patients undergoing substrate-based ablation of left posterior fascicular ventricular tachycardia (LPF-VT) guided by targeting of fragmented antegrade Purkinje potentials (FAPs) during sinus rhythm.

METHODS AND RESULTS

This study retrospectively analysed 50 consecutive patients referred for ablation. Substrate mapping during sinus rhythm was performed to identify the FAP that was targeted by ablation. FAPs were recorded in 48 of 50 (96%) patients during sinus rhythm. The distribution of FAPs was located at the proximal segment of posterior septal left ventricle (LV) in two (4.2%) patients, middle segment in 33 (68.8%) patients, and distal segment in 13 (27.1%) patients. In 32 of 48 (66.7%) patients, the FAP displayed a continuous multicomponent fragmented electrogram, while a fragmented, split, and uncoupled electrogram was recorded in 16 (33.3%) patients. Entrainment attempts at FAP region were performed successfully in seven patients, demonstrating concealed fusion and the critical isthmus of LPF-VT. Catheter ablation targeting at the FAPs successfully terminated the LPF-VT in all 48 patients in whom they were seen. Left posterior fascicular (LPF) block occurred in four (8%) patients after ablation. During a median follow-up period of 61.2 ± 16.8 months, 47 of 50 (94%) patients remained free from recurrent LPF-VT.

CONCLUSION

Ablation of LPF-VT targeting FAP during sinus rhythm results in excellent long-term clinical outcome. FAPs were commonly located at the middle segment of posterior septal LV. Region with FAPs during sinus rhythm was predictive of critical site for re-entry.

Confounding factors leading to misdiagnosing ventricular tachycardia as supraventricular in the emergency room

Studies conducted during the last 50 years have proposed electrocardiographic criteria and algorithms to determine if a wide QRS tachycardia is ventricular or supraventricular in origin. Sustained ventricular tachycardia is an uncommon reason for consultation in the emergency room. The latter and the complexity of available electrocardiographic diagnostic criteria and algorithms result in frequent misdiagnoses. Good hemodynamic tolerance of tachycardia in the supine position does not exclude its ventricular origin. Although rare, ventricular tachycardia in patients with and without structural heart disease may show a QRS duration <120 ms. Interruption of tachycardia by coughing, carotid sinus massage, Valsalva maneuver, or following the infusion of adenosine or verapamil should not discard the ventricular origin of the arrhythmia. In patients with regular, uniform, sustained broad QRS tachycardia, the presence of structural heart disease or A-V dissociation strongly suggest its ventricular origin. Occasionally, ventricular tachycardia can present with AV dissociation without this being evident on the 12-lead ECG. Cardiac auscultation, examination of the jugular venous pulse, and arterial pulse palpation provide additional clues for identifying A-V dissociation during tachycardia. This paper does not review the electrocardiographic criteria for categorizing tachycardia as ventricular but rather why emergency physicians misdiagnose these patients.

[Anatomy of the left ventricle for endocardial ablation]

As with all cardiac interventions, performing left ventricular ablation requires profound knowledge of cardiac anatomy. The aim of this article is to provide an overview of left ventricular anatomy and to characterize complex and clinically relevant structures from an electrophysiologist-centered perspective. In addition to the different access routes, the trabecular network, the left ventricular outflow tract, and the left ventricular conduction system, complex anatomical structures such as the aortomitral continuity and the left ventricular summit are also explained. In addition, this article offers multiple clinical examples that combine ECG, anatomy, and electrophysiologic study.

Differentiating left bundle branch pacing and left ventricular septal pacing: An algorithm based on intracardiac electrophysiology

BACKGROUND

Left bundle branch pacing (LBBP) is a new near-physiological pacing modality. Distinguishing left ventricular septal only pacing (LVSP) from nonselective LBBP still needs clarification. This prospective study sought to establish a differentiation algorithm to confirm LBBP.

METHODS AND RESULTS

LBBP was attempted in consecutive patients. If direct LBB capture (LBBP) could not be confirmed, LVSP was considered to have been achieved. Intracardiac left ventricular (LV) activation sequence and activation time were analyzed using coronary sinus (CS) electrogram mapping. Electrophysiological parameters including S-CSmax, S-CSmin, LV lateral wall activation time, ΔLV, and LBB potential were compared between LBBP and LVSP. Stimulated LV activation time (S-LVAT) and stimulated QRS duration (S-QRSd) were also compared between the two groups. Multivariate logistic regression analysis was used to develop a prediction algorithm for LBBP. Of the 43 prospectively enrolled patients, 27 underwent LBBP and 16 underwent LVSP. All LBBP patients showed identical LV activation sequences to their intrinsic rhythm while no LVSP patients maintained their intrinsic sequence. S-CSmax, ΔLV, LV lateral wall activation time, and S-LVAT during LBBP were significantly shorter than those during LVSP. Combining LBB potential with S-LVAT had the largest area under the curve (AUC) of 0.985 for confirming LBBP with a sensitivity of 95.2% and a specificity of 93.7%.

CONCLUSIONS

Compared with LVSP, LBBP preserves a normal LV activation sequence and better electrical synchrony. A combination of LBB potential with S-LVAT can be an effective and practical model to distinguish LBBP from LVSP during implantation in patients with normal LBB activation.

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.

Anatomy and Pathology of the Cardiac Conduction System

The cardiac conduction system is formed of histologically and electrophysiologically distinct specialized tissues uniquely located in the human heart. Understanding the anatomy and pathology of the cardiac conduction system is imperative to an interventional electrophysiologist to perform safe ablation and device therapy for the management of cardiac arrhythmias and heart failure. The current review summarizes the normal and developmental anatomy of the cardiac conduction system, its variation in the normal heart and congenital anomalies, and its pathology and discusses important clinical pearls for the proceduralist.

Magnetic Resonance Features of a Recent Catheter Ablation of Left Posterior Fascicular Ventricular Tachycardia

A 71-year-old male patient with a past medical history of hypertension, hyperlipidemia, and chronic kidney disease stage II presented with a complaint of intermittent palpitations for three months and was found to have wide complex tachycardia on the electrocardiogram (ECG). The patient was given adenosine and amiodarone, following which he underwent synchronized cardioversion at 150 Joules followed by 200 Joules without successful conversion. He was subsequently initiated on lidocaine drip at the rate of 1 to 4 mg/minute to maintain adequate rhythm control, which converted him to sinus rhythm and relieved his symptoms. An eventual assessment with an electrophysiology study identified the presence of incessant left ventricular tachycardia (VT). The mechanism was confirmed to be left posterior fascicular ventricular tachycardia (LPF-VT). Successful mapping and ablation for the LPF-VT were achieved. Post-procedure cardiac MRI showed two small areas of near-transmural delayed enhancement. These areas are associated with nulled areas in the inferolateral wall at the left posterior His-Purkinje fascicle. This case highlights fascicular VT as a separate clinical entity, with its characteristic ECG features and acute MRI features after ablation.

On the nature of delays allowing anatomical re-entry involving the Purkinje network: a simulation study

AIMS

Clinical observations suggest that the Purkinje network can be part of anatomical re-entry circuits in monomorphic or polymorphic ventricular arrhythmias. However, significant conduction delay is needed to support anatomical re-entry given the high conduction velocity within the Purkinje network.

METHODS AND RESULTS

We investigated, in computer models, whether damage rendering the Purkinje network as either an active lesion with slow conduction or a passive lesion with no excitable ionic channel, could explain clinical observations. Active lesions had compromised sodium current and a severe reduction in gap junction coupling, while passive lesions remained coupled by gap junctions, but modelled the membrane as a fixed resistance. Both types of tissue could provide significant delays of over 100 ms. Electrograms consistent with those obtained clinically were reproduced. However, passive tissue could not support re-entry as electrotonic coupling across the delay effectively increased the proximal refractory period to an extremely long interval. Active tissue, conversely, could robustly maintain re-entry.

CONCLUSION

Formation of anatomical re-entry using the Purkinje network is possible through highly reduced gap junctional coupling leading to slowed conduction.

Empirical Ablation to Prevent Sequential Purkinje System Recruitment: A Novel Therapy for Idiopathic Ventricular Fibrillation

We report 3 cases (mean age 48.3 ± 11.6 years) of idiopathic ventricular fibrillation (IVF), in which a triggering premature ventricular complex leading to IVF could not be identified. All patients underwent posterior fascicle transection with empirical linear ablation of the mid-Purkinje potentials identified along the left ventricular interventricular inferior septum, and no ventricular fibrillation recurrence was documented in any of the patients. (Level of Difficulty: Advanced.)

Verapamil-sensitive idiopathic left ventricular tachycardia and concomitant atrioventricular nodal reentrant tachycardia

We describe the case of a young patient with runs of repetitive monomorphic left ventricular tachycardia. He was diagnosed with verapamil-sensitive, idiopathic left ventricular tachycardia (ILVT) and underwent an electrophysiological study, in which dual atrioventricular (AV) nodal physiology was evident, with an AV nodal reentrant tachycardia (AVNRT) being easily and reproducibly induced. Both the AVNRT and the ILVT were successfully ablated using high-density electroanatomical mapping and an open-irrigation catheter. In conclusion, verapamil-sensitive ILVT might coexist with AVNRT. In case of invasive therapy, a thorough electrophysiological evaluation is mandatory to exclude or treat other co-existing reentrant supraventricular arrhythmias.

Removing the complexity from wide complex tachycardia

Correctly diagnosing the cause of wide QRS tachycardias remain an area of difficulty for many clinicians. The authors provide a concise update to the different ECG algorithms that have been developed as well as caveats in their application.

Belhassen Ventricular Tachycardia in a Child

First reported in 1981, idiopathic left ventricular tachycardia (VT) of the Belhassen type is characterized during electrocardiography (ECG) by a right bundle branch pattern and left axis deviation. We report the case of a 15-year-old Hispanic male who, during a routine evaluation ECG to support sports participation, was found to have nonsustained monomorphic VT. Prior to his exercise treadmill test, his physical examination and echocardiogram were normal. Then, during preparation for the exercise treadmill test, the ECG showed sustained monomorphic VT with a right bundle branch block pattern and superior QRS axis, suggesting a diagnosis of Belhassen VT.

Case Report: Recurrent Left Posterior Fascicular Ventricular Tachycardia in a Newborn

Left posterior fascicular ventricular tachycardia (LPFVT) is extremely rare in neonates. We described a 17-day-old girl with LPFVT who was initially misdiagnosed as supraventricular tachycardia (SVT). Eventually, she was successfully treated by amiodarone infusion followed by oral amiodarone with propranolol for 9 months, and LPFVT spontaneously resolved after a 1-year follow-up. This case report illustrated the basic principles and caveats in differential diagnosis of LPFVT in the neonatal age group. With proper diagnosis and therapy, neonatal LPFVT might regress in the first year of life.

Belhassen Syndrome in Teenager Originating from Left Anterior Fascicle

A 16-year-old female patient was hospitalized due to narrow QRS tachycardia suggestive of fascicular ventricular tachycardia. Initially, the differential diagnosis with supraventricular tachycardia can be challenging. The tachyarrhythmia is well controlled with medication, but electrophysiological study and ablation may be necessary in patients who remain symptomatic.

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.

Management of ventricular electrical storm: a contemporary appraisal

Ventricular electrical storm (VES) is a clinical scenario characterized by the clustering of multiple episodes of sustained ventricular arrhythmias (VA) over a short duration. Patients with VES are prone to psychological disorders, heart failure decompensation, and increased mortality. Studies have shown that 10–28% of the patients with secondary prevention ICDs can sustain VES. The triad of a susceptible electrophysiologic substrate, triggers, and autonomic dysregulation govern the pathogenesis of VES. The rate of VA, underlying ventricular function, and the presence of implantable cardioverter-defibrillator (ICD) determine the clinical presentation. A multi-faceted approach is often required for management consisting of acute hemodynamic stabilization, ICD reprogramming when appropriate, antiarrhythmic drug therapy, and sedation. Some patients may be eligible for catheter ablation, and autonomic modulation with thoracic epidural anesthesia, stellate ganglion block, or cardiac sympathetic denervation. Hemodynamically unstable patients may benefit from the use of left ventricular assist devices, and extracorporeal membrane oxygenation. Special scenarios such as idiopathic ventricular fibrillation, Brugada syndrome, Long and short QT syndrome, early repolarization syndrome, catecholaminergic polymorphic ventricular tachycardia, arrhythmogenic right ventricular cardiomyopathy, and cardiac sarcoidosis have been described as well. VES is a cardiac emergency that requires swift intervention. It is associated with poor short and long-term outcomes. A structured team-based management approach is paramount for the safe and effective treatment of this sick cohort.

Catheter ablation of left posterior fascicular ventricular tachycardia in children with limited fluoroscopy exposure

INTRODUCTION

Catheter ablation of left posterior fascicular ventricular tachycardia in the pediatric population remains challenging, and most studies about this topic have been conducted on adult patients. This study aimed to assess the clinical presentation features and outcomes of catheter ablations performed using limited fluoroscopy with three-dimensional electroanatomic mapping system guidance in a pediatric left posterior fascicular ventricular tachycardia patient group.

METHODS

A total of 20 consecutive patients undergoing left posterior fascicular ventricular tachycardia ablation at a single tertiary centre were enrolled. All children with left posterior fascicular ventricular tachycardia underwent electrophysiological studies using the EnSite NavX system guidance. Ablations were performed during the sinus rhythm based on the Purkinje potentials in all patients.

RESULTS

The mean patient age was 12.7 years (range 2-16), and the mean patient weight was 51 kg (range 11-84). The mean procedure and median fluoroscopy times were 143.1 minutes and 3.4 minutes, respectively. No fluoroscopy was used in three patients. Acute success was achieved in 19 patients (95%). During a mean follow-up of 38.6 ± 19.35 months, left posterior fascicular ventricular tachycardia recurred in four patients (20%). Repeat ablations were performed successfully in those patients who developed recurrences. No complications were seen.

CONCLUSIONS

Catheter ablation of left posterior fascicular ventricular tachycardia in children can be performed safely and effectively with low fluoroscopy exposure using a three-dimensional electroanatomic mapping system.