Atriofascicular connection or a nodoventricular Mahaim fiber? Electrophysiologic elucidation of the pathway and...

Area of Science:

• Electrophysiology
• Cardiology

Background:

• Accessory pathways with decremental properties inserting into the right ventricle are often termed "nodoventricular" or Mahaim pathways.
• Conclusive evidence for a nodal origin of these pathways is lacking, necessitating further investigation into their true nature.

Observation:

• A patient presented with characteristics typical of a nodoventricular pathway, exhibiting decremental, nodelike conduction properties antegradely.
• Right bundle branch recordings confirmed the pathway's direct insertion into the right bundle branch.
• Atrioventricular reciprocating tachycardia was readily inducible, with a left bundle branch block pattern during tachycardia and normal QRS during sinus rhythm.

Findings:

• The reentrant circuit involved antegrade conduction via the accessory pathway and retrograde conduction through the His-Purkinje system and atrioventricular node.
• Late atrial stimuli during tachycardia pre-excited the ventricle via the accessory pathway, bypassing the atrioventricular node.
• The study identified the upper "turn around" of the reentrant circuit involving atrial tissue, with the accessory pathway originating directly from the right atrium, independent of the atrioventricular node.

Implications:

• These findings challenge the traditional definition of nodoventricular pathways.
• A reassessment of "nodoventricular" fibers is warranted, suggesting many may be atriofascicular or atrioventricular connections with decremental properties.
• This research contributes to a more accurate understanding of accessory pathway anatomy and electrophysiology in cardiac arrhythmias.