Adenosine-sensitive decremental conduction over short non-decremental atrioventricular accessory pathways after...

Decremental conduction in short anterograde atrioventricular accessory pathways (AV-APs) is rare.

We report on two cases with radiofrequency (RF) ablation of anterograde fast non-decremental AV-AP conduction. In Case 1, electrophysiological testing revealed fast non-decremental conduction over an anterograde short right posteroseptal AV-AP. During ablation, latent pre-excitation due to anterograde adenosine-sensitive slow decremental conduction over the same AV-AP manifested after eliminating its non-decremental conduction. Complete abolition of AP conduction was achieved by additional ablation. In Case 2, overt pre-excitation disappeared after the first ablation session for an anterograde short non-decremental right mid-septal AV-AP. However, latent pre-excitation due to markedly decremental conduction over the same AV-AP unmasked by intravenous adenosine and atrial pacing manoeuvers could be eliminated in a second session.

This report describes unusual anterograde short non-decremental AV-APs, developing markedly slow adenosine-sensitive decremental conduction during ablation. Such AV-AP conduction properties due to RF injury may be overlooked and mask incomplete ablation and point-out careful testing including stimulation techniques and low and higher dose adenosine administration post-ablation.