Adenosine, when given as an intravenous bolus, has been shown to produce atrioventricular nodal block in humans. To examine the effect of adenosine on conduction across both accessory pathways and the atrioventricular node in children, we reviewed our experience with adenosine administered during both atrial and ventricular pacing in 42 patients with atrioventricular resting tachycardia and in eight patients with atrioventricular nodal reentry tachycardia. Adenosine was administered as a mean bolus of 195 μg/kg/dose during both atrial and ventricular pacing, examining antegrade and retrograde conduction before and after radiofrequency ablation. In those patients with persistent or intermittent pre-excitation, anomalous ventricular activation was either unchanged (n=8) or increased (n=11). Retrograde conduction (either through the accessory pathway alone in three, or across both the accessory pathway and the atrioventricular node in 19) persisted in 92% of the 24 patients studied. Adenosine produced either first or third degree antegrade heart block in all patients studied without pre-excitation (those with either dual atrioventricular nodal pathways or concealed accessory pathways). Adenosine produced retrograde block in all of the eight patients with dual atrioventricular nodal pathways. In contrast, retrograde conduction persisted in 82% (147 17) of patients with concealed accessory pathways (p=0.001). When used to examine retrograde conduction, adenosine was a sensitive (82%) and highly specific (producing retrograde atrioventricular block in all patients with dual atrioventricular nodal pathways) predictor of tachycardia supported by a concealed accessory pathway. Adenosine yielded a sensitivity and specificity of 96% and a positive predictive value of 99.5% for the success of ablation of accessory pathways. These data indicate that the pattern of adenosine-induced changes in either antegrade or retrograde atrioventricular conduction, or conduction in both directions, in young patients with supraventricular tachycardia is related to the mechanism of the tachycardia. Adenosine, therefore, is a useful adjunct in the electrophysiologic evaluation of supraventricular tachycardia in children.
- Accessory pathway
- Atrioventricular node