Radiofrequency catheter ablation of atriofascicular accessory pathways guided by discrete electrical potentials recorded at the tricuspid annulus

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.

Atriofascicular pathway detection with novel ablation catheter

Atriofascicular pathways are a rare cause of antidromic atrioventricular reciprocating tachycardia. The IntellaTip MiFi ablation catheter (Boston Scientific, MA, USA) is a novel ablation catheter that allows enhanced signal clarity with highly localized electrograms. This is the first report of this catheter being successfully used to map and ablate the atriofascicular pathway potentials.

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.

Anatomic and electrophysiologic evaluation of a right lateral atrioventricular Mahaim fiber

We report a patient who underwent an electrophysiologic study and radiofrequency catheter ablation for a right lateral Mahaim fiber. During sinus rhythm with overt preexcitation, propagation mapping was performed in the right ventricle using a three-dimensional electro-anatomical mapping system (CARTO). Small discrete potentials, which reflected the excitation of the Mahaim fiber, could be recorded along the line from the vicinity of the parental tricuspid annulus to approximately one-third of distal site from the base to the apex. The relationship of the timing of its potential to the anatomical location could be disclosed on recordings of the local electrogram and anatomical map.

The 12-lead ECG in patients with Mahaim fibers

The aim of this review article is to discuss the electrocardiographic presentation of the so called variants of pre-excitation ("Mahaim fibers") during sinus rhythm and tachycardia.

Radiofrequency ablation of right-sided accessory pathways in pediatric patients

Right free-wall and septal accessory pathways encompass the full spectrum of accessory pathway electrophysiology and are situated in complex anatomical arrangements. Understanding this diversity of physiology is necessary for the successful and safe elimination of these connections with transcatheter radiofrequency ablation. When radiofrequency catheter ablation of these pathways is attempted in children, anatomical relationships often become more complex, and spatial constraints require more adaptive techniques than in adults. It is clear that considerable progress has been made with radiofrequency catheter ablation, such that it is now first-line therapy for most children who have been diagnosed with one of the broad spectrum of clinical manifestations that result from the presence of these accessory connections. This review will discuss how accessory pathway electrophysiology and anatomy impact the clinical syndromes observed in children, and how these factors, as well as others particular to children, determine the approach, results and potential long-term consequences of radiofrequency catheter ablation of right-sided accessory pathways in the pediatric population.

Electrophysiologic characteristics and radiofrequency ablation of concealed nodofascicular and left anterograde atriofascicular pathways

INTRODUCTION

True nodoventricular or nodofascicular pathways and left-sided anterograde decremental accessory pathways (APs) are considered rare findings.

METHODS AND RESULTS

Two unusual patients with paroxysmal supraventricular tachycardia were referred for radiofrequency (RF) ablation. Both patients had evidence of dual AV nodal conduction. In case 1, programmed atrial and ventricular stimulation induced regular tachycardia with a narrow QRS complex or episodes of right and left bundle branch block not altering the tachycardia cycle length and long concentric ventriculoatrial (VA) conduction. Ventricular extrastimuli elicited during His-bundle refractoriness resulted in tachycardia termination. During the tachycardia, both the ventricles and the distal right bundle were not part of the reentrant circuit. These findings were consistent with a concealed nodofascicular pathway. RF ablation in the right atrial mid-septal region with the earliest atrial activation preceded by a possible AP potential resulted in tachycardia termination and elimination of VA conduction. In case 2, antidromic reciprocating tachycardia of a right bundle branch block pattern was considered to involve an anterograde left posteroseptal atriofascicular pathway. For this pathway, decremental conduction properties as typically observed for right atriofascicular pathways could be demonstrated. During atrial stimulation and tachycardia, a discrete AP potential was recorded at the atrial and ventricular insertion sites and along the AP. Mechanical conduction block of the AP was reproducibly induced at the annular level and at the distal insertion site. Successful RF ablation was performed at the mitral annulus.

CONCLUSION

This report describes two unusual cases consistent with concealed nodofascicular and left anterograde atriofascicular pathways, which were ablated successfully without impairing normal AV conduction system.

Radiofrequency ablation of a right atriofascicular Mahaim fiber and two contralateral left free-wall accessory pathways

We report a rare combination of a right atriofascicular Mahaim fiber and two left-sided atrioventricular accessory pathways in a 57-year-old female presenting with an antidromic atrioventricular reciprocating tachycardia. Radiofrequency ablation was first targeted at the left lateral accessory pathway that served as the retrograde limb of the tachycardia. After elimination of the left lateral pathway, a bystander left posterolateral pathway was detected, and it too was successfully ablated. Although no tachycardia was reinducible, the Mahaim pathway was ablated because of its short effective refractory period. A discrete Mahaim potential recorded at the right atrial free-wall successfully guided the ablation.

Radiofrequency ablation of a concealed nodoventricular Mahaim fiber guided by a discrete potential

INTRODUCTION

We present the case of a 17-year-old woman who underwent an electrophysiological study and radiofrequency (RF) ablation of supraventricular tachycardia refractory to medical treatment. Two right-sided, concealed, nondecremental atrioventricular accessory pathways (AV-APs) involved in orthodromic circus movement tachycardias were identified. After RF ablation of both AV-APs, evidence of bidirectional dual AV nodal conduction was demonstrated and regular narrow complex tachycardia was induced.

METHODS AND RESULTS

During the tachycardia, retrograde slow and fast AV nodal pathway conduction with second-degree ventriculoatrial (VA) block and VA dissociation were observed. During the tachycardia with second-degree VA block, ventricular extrastimuli elicited during His-bundle refractoriness advanced the next His potential or terminated the tachycardia. Mapping the right atrial mid-septal region, a distinct high-frequency activation P potential was recorded in a discrete area, two thirds of the way from the His bundle toward the os of the coronary sinus. Detailed electrophysiologic testing with the recordable P potential demonstrated that the tachycardia utilized a concealed nodoventricular AP arising from the proximal slow AV nodal pathway.

CONCLUSION

The tachycardia with slow 1:1 VA conduction could be reset by ventricular extrastimuli elicited during His-bundle refractoriness advancing the subsequent activation P potential and atrial activation. RF ablation guided by recording of the activation P potential resulted in elimination of both the slow AV nodal pathway and the nodoventricular connection with preservation of the normal AV conduction system.

Radiofrequency catheter ablation of two right Mahaïm-like accessory pathways in a patient with Ebstein's anomaly

A 17-year-old woman with Ebstein's anomaly and recurrent episodes of antidromic tachycardia with two distinct morphologies is described. The tachycardias were produced by two separate Mahaïm-like accessory pathways. These were localized by their activation potentials at the anterolateral ventricular margin of the tricuspid annulus and ablated in a single session using radiofrequency current.

New electrophysiologic features and catheter ablation of atrioventricular and atriofascicular accessory pathways: evidence of decremental conduction and the anatomic structure of the Mahaim pathway

INTRODUCTION

Several modalities of catheter ablation have been proposed to eliminate Mahaim pathway conduction. However, limited research has been reported on the electrophysiologic nature of this pathway in its entity.

METHODS AND RESULTS

In seven patients, electrophysiologic study was performed, and radiofrequency energy was applied to investigate the electrophysiologic clues for successful ablation. In all seven patients, the Mahaim pathway was diagnosed as a right-sided atriofascicular or atrioventricular pathway with decremental properties. In two patients, two different kinds of electrograms were recorded through the ablation catheter positioned at the Mahaim pathway location: one was suggestive of conduction over the decremental portion, demonstrating a dulled potential; and the other of nondecremental conduction, demonstrating a spiked potential. All but one of the Mahaim pathways were eliminated successfully at the atrial origin where the spiked Mahaim potential was recorded. Radiofrequency energy application was performed at the slow potential site resulting in failure to eliminate the conduction over the Mahaim pathway. Conduction block at the site between the slow and fast potential recording sites was provoked by intravenous administration of adenosine, concomitant with a decrease in the amplitude of the Mahaim potential. In one patient, the clinical arrhythmia was a sustained monomorphic ventricular tachycardia originating from the ventricular end of the Mahaim fiber.

CONCLUSION

The identification of Mahaim spiked potentials may be the optimal method to permit their successful ablation. Detailed electrophysiologic assessment is indispensable for successful ablation of tachycardias associated with Mahaim fibers because tachycardias unassociated with Mahaim fibers can occur despite complete elimination of the Mahaim fiber.