[Accessory atrioventricular pathways with decremental conduction (Mahaim connections). 2 case reports]

Area of Science:

• Cardiology
• Electrophysiology

Background:

• Mahaim connections are a rare cause of preexcitation syndrome.
• They are characterized by antidromic atrioventricular reentry tachycardia with a wide QRS complex resembling left bundle branch block morphology.

Observation:

• Nodofascicular and nodoventricular fibers, though rare, are implicated in Mahaim connections.
• Most accessory pathways are located on the right free wall, conducting antegradely and decrementally, often inserting into the right bundle branch or ventricular apex.

Findings:

• Traditional mapping strategies are often ineffective for these pathways.
• Two case reports highlight Mahaim connections: one masked a conduction disturbance, while the other involved a successfully mapped and ablated right anterolateral accessory pathway causing characteristic symptoms.

Implications:

• Specialized mapping and ablation approaches are necessary for diagnosing and treating Mahaim connections.
• Understanding these rare accessory pathways is crucial for managing complex tachycardia and conduction disturbances.