Minimally decremental atriofascicular accessory pathway with bidirectional conduction.

Atriofacicular pathways of Mahaim type are typically decrementally conducting accessory pathways without retrograde conduction properties, located on the right ventricular free wall at the tricuspid annulus. We report a patient with an atriofascicular pathway with minimal anterograde decremental conduction. Both long and short V-H antidromic atriofascicular reentrant tachycardias were induced and mechanism confirmed with electrophysiologic testing. Additionally, orthodromic atriofascicular reentrant tachycardia with narrow and right bundle branch block morphologies were inducible. Mahaim pathway was successfully ablated with elimination of both antidromic and orthodromic tachycardias.

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.

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.

Ablating the ventricular insertion of atrio-fascicular mahaim fiber: could be performed safely?

We report a patient who underwent radiofrequency ablation of the distal insertion of an atrio-fascicular accessory pathway with decremental properties because of inability to map a suitable potential alongside the tricuspid annulus. Small, discrete potentials resembling those of Purkinje fiber were found at right ventricular apex. All these potentials showed early activation during tachycardia preceding the QRS onset of various degree. Pace mapping helped to localize the presumed main distal insertion of the atrio-fascicular accessory pathway in a region where damage of the His-purkinje system may ensue. This case report describes catheter ablation of an atriofascicular accessory pathway by targeting its distal (ventricular) insertion site.

Looks like VT But Isn't--successful ablation of a left free wall accessory pathway with Mahaim-like properties.

It was long believed that Mahaim pathways represented nodo-fascicular or nodo-ventricular connections. However, this misconception was challenged when patients underwent surgical or catheter ablation of the AV node but remained pre-excited. Electrophysiology (EP) studies showed these pathways to be right sided decrementally conducting atrio-fascicular accessory pathways with the atrium forming a part of the antidromic tachycardia circuit. Mahaim pathways are usually reported to occur on the right side. We report a patient who presented with a broad complex tachycardia thought to be ventricular tachycardia; however during EP study this was shown to be an antidromic atrioventricular tachycardia utilising a left free wall pathway that demonstrated 'Mahaim-like' properties and was successfully ablated. The pathway was shown to have long conduction times with no retrograde conduction, had an effective refractory period longer than the AV node and its conduction was only evident during antidromic AVRT. It also had a decremental antegrade property and was responsive to intravenous adenosine. These 'Mahaim-like' features are very unusual and rarely reported on the left side.

A Wide Complex Tachycardia in a Structurally Normal Heart: What is the Mechanism? Where to Ablate?

We present a case of wide complex tachycardia (left bundle branch block, superior axis) in a 30-year-old female with a structurally normal heart and no baseline preexcitation on electrocardiogram. Tachycardia initiation and atrial pacing confirmed the existence and participation of a right-sided atriofascicular decrementally conducting Mahaim pathway. Tachycardia mechanism validation by atrial pacing maneuvers was documented as well as was a response to adenosine and preexcited Mahaim atrial fibrillation. The usual ablation site did not record a Mahaim potential; hence, ablation was performed at a site other than the usual one.