[Radiofrequency transcatheter ablation of a bidirectional decremental accessory atrioventricular pathway in the coronary sinus]

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Anatomy

Background:

• Atrioventricular accessory pathways (APs) can exhibit decremental conduction properties, typically anterograde.
• Mahaim-type APs are generally right-sided with atrial insertions along the tricuspid ring.
• Retrograde decremental conduction in APs is uncommon.

Observation:

• A 63-year-old patient presented with an atrioventricular accessory pathway.
• The pathway demonstrated unusual bidirectional decremental conduction properties.
• Radiofrequency catheter ablation successfully targeted the pathway's origin.

Findings:

• The ablation site was identified at the distal end of a wedge-shaped dilation in the first tract of the coronary sinus.
• This represents a rare left-sided AP with decremental conduction.
• The pathway's location within the coronary sinus is unprecedented for Mahaim-type pathways.

Implications:

• This case expands the known anatomical and electrophysiological spectrum of atrioventricular accessory pathways.
• It suggests Mahaim-type pathways may occur in locations previously considered impossible.
• Findings may necessitate re-evaluation of diagnostic criteria and ablation strategies for complex APs.