ADENOSINE-INDUCED ATRIOVENTRICULAR-BLOCK - A RAPID AND RELIABLE METHOD TO ASSESS SURGICAL AND RADIOFREQUENCY CATHETER ABLATION OF ACCESSORYATRIOVENTRICULAR PATHWAYS

Adenosine has been shown to inhibit anterograde and retrograde conduct ion through the atrioventricular (AV) node while having little or no e ffect on accessory pathway conduction. Its rapid onset of action and s hort half-life make it particularly suitable for repetitive measuremen ts. In this study, the utility of adenosine was tested in assessing co mpleteness of accessory pathway ablation. Sixteen patients with an acc essory pathway were studied (eight surgical ablations, eight catheter ablations with radiofrequency energy). Before ablation, no accessory p athway was sensitive to adenosine. Twelve patients with pre-excitation showed high grade AV node block with maximal pre-excitation on the ad ministration of adenosine during atrial pacing. Four patients with a c oncealed accessory pathway demonstrated high grade AV block without ev idence of latent anterograde accessory pathway conduction. Preablation ventriculoatrial (VA) block was not observed in any of the 16 patient s in response to adenosine during ventricular pacing. Immediately afte r accessory pathway ablation, all patients developed AV and VA block w ith the administration of adenosine during atrial and ventricular paci ng, respectively. These findings were confirmed during follow-up study 1 week later. Atrioventricular block during atrial and ventricular pa cing with adenosine affords a reliable and immediate assessment of suc cessful pathway ablation.