Automaticity in Mahaim Fibers

Sternick, Eduardo Back; Sosa, Eduardo; Timmermans, Carl; Filho, Fernando E. Cruz; Rodriguez, Luz‐Maria; Gerken, Luíz Márcio; Scanavacca, Maurício; Fagundes, Márcio; Bueno, Sávia Christina Pereira; Vrandecic, Mário Osvaldo; Wellens, Hein J.J.

doi:10.1046/j.1540-8167.2004.03615.x

Cited by 55 publications

(44 citation statements)

References 18 publications

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“…The potential presence of AV node-like cells in these pathways is supported by the occurrence of spontaneous automaticity in Mahaim fibers, as reported recently. 3 However, the mechanism whereby nodal cells, possibly underlying the frequency-dependent propagation of these tracts, may be present at this site, remains unclear.…”

Section: Discussionmentioning

confidence: 99%

“…The proximal insertion of these fibers is localized to the lateral, anterolateral, or posterolateral part of the tricuspid annulus; distally the fibers connect to the right ventricular free wall or the right bundle branch. 1,2 The origin of Mahaim fibers and their functional characteristics (such as AV node-like conduction properties and, as recently reported, spontaneous automaticity 3 ) have not yet been explained.…”

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confidence: 95%

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Development of the Right Ventricular Inflow Tract and Moderator Band

Jongbloed

Wijffels

Schalij

et al. 2005

Circulation Research

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Abstract-Atriofascicular accessory bundles with AV-node like conduction properties can sustain atrioventricular (AV) re-entrant tachycardia (Mahaim tachycardia). During early embryogenesis, the AV canal is situated above the primitive left ventricle (LV), and a right AV connection has not been achieved yet. We studied the formation of the right ventricular (RV) inflow tract in relation to the developing cardiac conduction system and hypothesized a morphological explanation for functional atriofascicular bypass tracts. Analysis of lacZ-expression during sequential stages of cardiogenesis was performed in CCS-lacZ transgenic mice (E9.5 to 15.5). Embryos were stained for ␤-galactosidase activity and the myocardial marker HHF35. At early stages CCS-lacZ expression was observed in a ring surrounding the AV canal, which connected at the inner curvature to the primary fold. The first sign of formation of the (CCS-lacZ negative) RV inlet component was a groove in the CCS-lacZ positive tissue of the primary fold. Outgrowth of the RV inlet tract resulted in division of the primary fold in a septal part, the trabecula septomarginalis and a lateral part, the moderator band, which extended laterally up to the right AV ring. Electrophysiological measurements in embryonic hearts (E15.5) in which the right atrium (RA) and RV were isolated from the left atrium (LA) and LV supported the functionality of this AV-connection via the moderator band, by demonstrating sequential atrial and ventricular activation in both RA/RV and LA/LV preparations. In conclusion, our observations may provide a possible morphological and functional explanation for atriofascicular accessory pathways via the moderator band, underlying Mahaim tachycardia.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 95%

Development of the Right Ventricular Inflow Tract and Moderator Band

Jongbloed

Wijffels

Schalij

et al. 2005

Circulation Research

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“…Junctional rhythm with LBBB, bundle branch reentry using the RBB in an antegrade fashion, or Mahaim fiber automaticity [14][15][16][17] are all possibilities. However, endocardial recordings and pacing maneuvers can distinguish these types of arrhythmias.…”

Section: Diagnosis and The Possible Mechanismmentioning

confidence: 99%

Idiopathic Accelerated Idioventricular Rhythm or Ventricular Tachycardia Originating From the Right Bundle Branch

Chen

Yang

et al. 2014

Circ: Arrhythmia and Electrophysiology

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Background— Accelerated idioventricular rhythm (AIVR) or ventricular tachycardia (VT) originating from the right bundle branch (RBB) is rare and published clinical data on such arrhythmia are scarce. In this study, we will describe the clinical manifestations, diagnosis, and management of a cohort of patients with this novel arrhythmia. Methods and Results— Eight patients (5 men; median age, 25 years) with RBB-AIVR/VT were consecutively enrolled in the study. Pharmacological testing, exercise treadmill testing, electrophysiological study, and catheter ablation were performed in the study patients, and ECG features were characterized. All RBB-AIVR/VTs were of typical left bundle-branch block morphology with atrioventricular dissociation. The arrhythmias, which demonstrated chronotropic variability, were often isorhythmic with sinus rhythm and were accelerated by physical exercise, stress, and intravenous isoprenaline infusion. The rate of RBB-AIVR/VT varied from 45 to 200 beats per minute. Two patients experienced syncope, and 3 had impaired left ventricular function. Metoprolol was proven to be the most effective drug to decelerate the arrhythmia rate and relieve symptoms. Electrophysiology study was performed in 5 patients and the earliest activation with a sharp RBB potential was localized in the mid or distal RBB area. Catheter ablation terminated the arrhythmia with subsequent RBB block morphology during sinus rhythm. During follow-up, patients’ symptoms were controlled with normalization of left ventricular function either on metoprolol or by catheter ablation. Conclusions— RBB-AIVR/VT is an unusual type of ventricular arrhythmia. It can result in significant symptoms and depressed ventricular function and can be successfully treated with catheter ablation.

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“…Catheter ablation at a site with an "M" potential is likely to be successful. Automatic rhythms (MAT or Mahaim automatic rhythm) are observed during radio-frequency current delivery in most patients with atriofascicular and long AV fibers [26] (Figure 24.18a). It is probably due to heatrelated automaticity of nodal-like tissue as is also seen during slow AV nodal pathway ablation [27].…”

Section: Proximal End Mappingmentioning

confidence: 99%

“…MAT is in most cases short-lived but may sometimes last up to two minutes. At least in some patients it is necessary to completely terminate those rhythms to prevent recurrences [26] (Figure 24.18b).…”

Section: Proximal End Mappingmentioning

confidence: 99%

Cardiac Mapping in Variants of the Ventricular Preexcitation Syndrome

Sternick

Lokhandwala²,

Wellens

2012

Cardiac Mapping

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In this chapter we describe the identification, the structural-functional relation and the management of relatively rare intracardiac conduction pathways leading to variants of ventricular preexcitation. Their proper recognition is a must for the arrhythmologist involved in the ablative intracardiac treatment of these patients. Successively are discussed: atriofascicular pathways, short decrementally conducting accessory pathways, fasciculoventricular pathways, nodoventricular and nodofascicular pathways. Detailed information is given on how to use the appropriate electrophysiological maneuvers necessary to identify each of these variants, how to map them, and how to choose the best strategy for ablation, and how to document the success of that intervention. Special attention is given to the correct diagnosis of the fasciculoventricular pathways, when to be suspicious of the presence of a PRKAG2 mutation and how to correctly differentiate those from septal atrioventricular node (AV) pathways. Important knowledge to avoid the mistake of trying to ablate them with the potential of causing iatrogenic AV block, because they are not involved in tachycardia circuits.

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Automaticity in Mahaim Fibers

Abstract: Spontaneous automaticity occurred in 12.5% of our Mahaim patients and may trigger antidromic tachycardia. Spontaneous automaticity, which is not seen in rapidly conducting accessory pathways, is another argument for the presence of an AV nodal-like structure in Mahaim fibers.

Cited by 55 publications

References 18 publications

Development of the Right Ventricular Inflow Tract and Moderator Band

Development of the Right Ventricular Inflow Tract and Moderator Band

Idiopathic Accelerated Idioventricular Rhythm or Ventricular Tachycardia Originating From the Right Bundle Branch

Cardiac Mapping in Variants of the Ventricular Preexcitation Syndrome

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