Atriofascicular connection or a nodoventricular Mahaim fiber? Electrophysiologic elucidation of the pathway and associated reentrant circuit

Case report: Slow conducting accessory pathway in an Ebstein's anomaly patient: Is this a Mahaim fiber?

We report a case of multiple accessory pathways (APs) in an Ebstein's anomaly patient with a history of prior ablation. Electrophysiological study demonstrated a slow conducting AP which pre-excited ventricle only during atrial tachycardia or rapid atrial pacing. The non-decremental property and a longstanding fragment potential at the ablation target site rule out Mahaim fiber. The slow conducting AP might be caused by inadequate prior ablation, and highlights that delta wave absent and prolonged AV interval in target point could not definitely indicate anterograde conduction block when we ablate a manifest AP. Rapid atrial pacing may unveil the slow conducting AP.

High-density electroanatomic mapping of atriofascicular pathways using multipolar mapping catheters can identify oblique pathways and avoid mechanical bump termination

BACKGROUND

Atriofascicular fibers (AFFs) are rare accessory pathways that have higher rates of recurrence after ablation because of either failure to identify AFF (M) potentials or mechanical termination with contact.

OBJECTIVE

We aimed to evaluate whether electroanatomic mapping (EAM) using multielectrode, high-density nonlinear catheters can reliably localize AFF potentials and determine a site for ablation without causing mechanical termination.

METHODS

Seven patients underwent electrophysiology studies (EPS) and EAM using high-density, multielectrode catheters for antidromic tachycardia using AFFs.

RESULTS

Mean age at ablation was 15.5 ± 7.4 years, and 2 (29%) were female. Two had Ebstein's anomaly. Three of 7 (43%) had previous ablation attempts. Of the previous attempts, 3 (60%) were complicated by mechanical termination during mapping. None of the previous ablation attempts was performed using high-density mapping catheters. HD Grid with Ensite NavX (Abbott Cardiovascular, Abbott Park, IL) was used in 3; the remainder used the PentaRay (3) or Optrell (1) catheters with CARTO (Biosense Webster, Irvine, CA). The AFF course was mapped to the lateral tricuspid annulus in all. Four of 7 had oblique courses with atrial insertion superior to the ventricular insertion. Multielectrode mapping catheters did not result in mechanical termination in any of these cases, whereas mechanical termination with ablation catheters occurred in 4 (57%). Successful ablation was performed in all with no recurrence over a 15 ± 6-month follow-up.

CONCLUSION

EAM using high-density multielectrode mapping catheters allow localization of atriofascicular pathways without causing mechanical termination and may improve long-term success of ablation. Majority of the pathways had oblique courses with atrial insertion superior to the ventricular insertion.

Coexistence of a Classical Nodoventricular Accessory Pathway With a Left-Sided Mahaim Accessory Pathway

The coexistence of 2 Mahaim pathways represents a diagnostic challenge. We present a case in which the SH/HA intervals were useful for identifying concealed nodoventricular or His-ventricular pathways.

Bump termination of an atriofascicular tachycardia. Where is the level of block?

This electrophysiological tracing localizes the level of block distal to the recorded Mahaim potential during bump termination mapping of an atriofascicular pathway at the tricuspid annulus.

A very unusual wide QRS tachycardia: VT or SVT?

INTRODUCTION

A 13 old girl presented with recurrent wide QRS tachycardia since she was 4.

METHODS

An electrophysiologic study was performed.

RESULTS

The electrophysiologic study showed that QRS complexes identical to those of the tachycardia could be elicited with premature atrial extrastimuli but with a shorter atrioventricular (AV) delay when the QRS was wide compared with narrow QRS complexes. The tachycardia was ablated at 9 o'clock on the tricuspid annulus demonstrating the presence of an atriofascicular fiber.

CONCLUSION

We believe that this atypical behavior can be explained by AV nodal like longitudinal dissociation of a slowly conducting accessory pathway.

Comprehensive assessment of Mahaim accessory pathways' anatomic distribution

Objective

To present the authors’ experience of Mahaim-type accessory pathways (MAPs), focusing on anatomic localizations.

Methods

Data from consecutive patients who underwent electrophysiological study (EPS) for MAP ablation in two tertiary centres, between January 1998 and June 2020, were retrospectively analysed.

Results

Of the 55 included patients, 27 (49.1%) were male, and the overall mean age was 29.5 ± 11.6 years (range, 12–66 years). MAPs were ablated at the tricuspid annulus in 43 patients (78.2%), mitral annulus in four patients (7.3%), paraseptal region in three patients (5.5%), and right ventricle mid-apical region in five patients (9.1%). Among 49 patients who planned for ablation therapy, the success rate was 91.8% (45 patients).

Conclusion

MAPs were most often ablated at the lateral aspect of the tricuspid annuli, sometimes at other sides of the tricuspid and mitral annuli, and infrequently in the right ventricle. The M potential mapping technique is likely to be a useful target for ablation of MAPs.

Ablation of Accessory Pathways with Uncommon Electrophysiologic Properties

In rare cases, atrioventricular reentrant arrhythmias are sustained by accessory pathways with peculiar electrophysiologic features that may be related to their specific anatomy. Most of these bundles show decremental nodelike conduction properties and sustain peculiar forms of arrhythmias that require careful differential diagnosis. On the other hand, some pathways do not actively sustain any reentrant circuit and should nevertheless be promptly recognized to avoid unnecessary ablation attempts. Although rare, these variants of accessory pathway should be known to warrant a safe and effective catheter ablation procedure.

Arrhythmias Involving Variants of Accessory Pathways

In some cases, atrioventricular reentrant arrhythmias are sustained by accessory pathways with peculiar electrophysiologic properties related to their specific anatomy. Most of these fibers, which may be responsible for variants of ventricular preexcitation, show decremental conduction properties due to a nodelike aspect or a peculiar tortuous anatomic route across the atrioventricular groove. Moreover, some fibers do not actively sustain any reentrant circuit and can be only involved as bystander in other arrhythmias. Although rare, these accessory pathway variants should be properly diagnosed using noninvasive and invasive methods to guide catheter ablation procedures when needed.

Mahaim fiber connecting the right atrium to the left ventricle: a case report

In the majority of cases presenting with the Mahaim fiber (MF), the MF connects the lateral right atrium (RA) to the right bundle branch or the right ventricle. We present the case of a 33-year-old man with antidromic atrioventricular reentrant tachycardia using MF connected to the septal RA and left ventricle (LV). Although the Mahaim potential was recorded at the septal RA, ablation at this site could not eliminate the MF and had a potential risk of injury to the atrioventricular node. Additional application at the posterior septal LV achieved successful MF ablation.

Reflections on the early invasive clinical cardiac electrophysiology era through fifty manuscripts: 1967-1992

In 1967, researchers in The Netherlands and France independently reported a new technique, later called programmed electrical stimulation. The ability to reproducibly initiate and terminate arrhythmias heralded the beginning of invasive clinical cardiac electrophysiology as a medical discipline. Over the next fifty years, insights into the pathophysiologic basis of arrhythmias would transform the field into an interventional specialty with a tremendous armamentarium of procedures. In 2015, the variety and complexity of these procedures were major reasons that led to the recommendation for an increase in the training period from one year to two years. The purpose of this manuscript is to present fifty manuscripts from the early invasive clinical cardiac electrophysiology era, between 1967 and 1992, to serve as an educational resource for current and future electrophysiologists. It is our hope that reflection on the transition from a predominantly noninvasive discipline to one where procedures are commonly utilized will lead to more thoughtful patient care today and to inspiration for innovation tomorrow. In the words of the late Dr. Mark E. Josephson, "It is only by getting back to the basics that the field of electrophysiology will continue to grow instead of stagnate."

Mahaim fibers coexisting with coarctation of aorta and bicuspid aortic valve

We found a coexistence of Mahaim fibers, coarctation of aorta and bicuspid valve in a young patient presenting with palpitations and subraventricular tachycardia. This rare combination of these three congenital cardiac abnormalities occurring in the same patient has not been reported previously. Detailed cardiac studies unmasked the patient's cardiac abnormalities. Furthermore, successful percutaneous intervention in treating coarctation and catheter-based ablation of Mahaim fibers were performed with resolution of symptoms. This case is discussed here in detail, alongside a review of the literature.

Electro-vectorcardiographic and electrophysiological aspects of Ebstein's anomaly

Ebstein's anomaly is a congenital heart disease where the most important anatomic feature is the inferior displacement of the tricuspid valve leaflets. Vectorcardiographic features are mainly forgotten and electrocardiographic features may be unrecognized by cardiologists handling adult patients.

Atriofascicular Mahaim with Ebstein anomaly: A case report

We report a case of a 7-year-old girl with atriofascicular Mahaim (AFM) pathway concomitant with Ebstein's anomaly. The QRS wave showed left bundle branch block pattern on electrocardiogram. Holter electrocardiogram showed prolongation of the PR interval and QRS morphological change during sinus tachycardia. An electrophysiological study demonstrated that the distal His potential appeared earlier than the proximal His potential, which suggested retrograde His conduction toward the atrioventricular node. Conduction from the Mahaim fiber to the His bundle was faster than that from the atrioventricular node towards the His bundle. The findings of this important case allowed a differential diagnosis between AFM and Wolff-Parkinson-White (WPW) syndrome.

Mahaim Accessory Pathways

The term Mahaim conduction is conventionally used to describe decrementally conducting connections between the right atrium or the AV node and the right ventricle in or close to the right bundle branch. Although such pathways are rare, their unique properties make their diagnosis and treatment cumbersome. In this article we review the published evidence, and discuss the electrocardiographic and electrophysiological characteristics as well as the anatomy and origin of these fibres.

Human His-Purkinje System: Abnormalities of Conduction, Rhythm Disorders and Case Studies

This review covers many of the arrhythmias and conduction abnormalities related to His-Purkinje System. These include junctional premature complexes, junctional and fascicular tachycardias, bundle branch reentry (BBR), and the role of apparent conduction in various forms of supraventricular tachycardias (SVT) with or without involvement of accessory pathways (AP).

Preexcitation Syndromes

The classic electrocardiogram in Wolff-Parkinson-White (WPW) syndrome is characterized by a short PR interval and prolonged QRS duration in the presence of sinus rhythm with initial slurring. The clinical syndrome associated with above electrocardiogram finding and the history of paroxysmal supraventricular tachycardia is referred to as Wolff-Parkinson-White syndrome. Various eponyms describing accessory or anomalous conduction pathways in addition to the normal pathway are collectively referred to as preexcitation syndromes. The latter form and associated eponyms are frequently used in literature despite controversy and disagreements over their actual anatomical existence and electrophysiological significance. This communication highlights inherent deficiencies in the knowledge that has existed since the use of such eponyms began. With the advent of curative ablation, initially surgical, and then catheter based, the knowledge gaps have been mostly filled with better delineation of the anatomic and electrophysiological properties of anomalous atrioventricular pathways. It seems reasonable, therefore, to revisit the clinical and electrophysiologic role of preexcitation syndromes in current practice.

An unusual WPW syndrome: What is the preexcitation variant?

A 15-year-old female with WPW syndrome and normal heart underwent an electrophysiology study for paroxysmal palpitations and syncope. Intravenous adenosine produced an unexpected response of QRS changes and advanced AV block. During isoproteronol infusion, short-lasting and poorly tolerated wide QRS tachycardia was inducible, but pacing maneuvers were not feasible during tachycardia to determine its definitive mechanism. However, various electrophysiologic phenomena including adenosine response, junctional beats pattern, and multisite atrial pacing were helpful to overcome the diagnosis challenges. Finally, careful evaluation of tachycardia features and the comprehensive electrophysiology study were crucial to establish presence of unusual preexcitation variants, and thus to guide successful catheter ablation of the arrhythmic substrate.

Changing QRS Morphology in a Patient with Wolff-Parkinson-White Syndrome

A case of Wolff-Parkinson-White syndrome with supraventricular tachycardia is presented in which 2 atrioventricular (AV) reentry circuits are identified. The first circuit used the AV node in the antegrade limb and a left lateral accessory pathway in the retrograde limb. The second circuit used an atriofascicular accessory pathway as the antegrade limb and the left lateral accessory pathway as the retrograde limb. The characteristics of these tachycardias are described, along with diagnostic maneuvers used in the electrophysiology laboratory. Mapping and ablation of both of these accessory pathways is also described. This article is aimed at clinical electrophysiologists interested in management of complex supraventricular tachycardias in the electrophysiology laboratory.