Effects of Intravenous Adenosine on Antegrade Refractoriness of Accessory Atrioventricular Connections

Background. Several groups have suggested the use of intravenous adenosine or adenosine triphosphate in the diagnosis of regular broad complex tachycardias. However, the short half-life of these agents has precluded assessment of their effects on refractoriness of accessory connections, and their safety in preexcited arrhythmias has not been demonstrated. Methods and Results. We examined the effects of intravenous adenosine on accessory atrioventricular (AV) connections in 30 patients with the Wolff-Parkinson-White syndrome. Intravenous adenosine (12 mg, rapid bolus) was administered to 14 patients (group 1) during continuous atrial pacing at a cycle length 20 msec below that required to cause 2:1 conduction block in the accessory connection (mean pacing cycle length 261+41 msec). After adenosine, transient 1:1 conduction occurred via the accessory connection in 12 of 14 patients, indicating a shortening of antegrade refractoriness. In three of seven patients, this effect was abolished after intravenous propranolol (0.2 mg/kg). Nineteen patients (group 2) received adenosine (0.17±0.04 mg/kg) during induced, preexcited atrial arrhythmias. The minimum RR interval during preexcited atrial fibrillation transiently decreased (252+±44 msec to 224±35 msec, p<0.01) after adenosine, but no change in average RR interval was observed (360 ± 59 msec t