Electrophysiologic effects of adenosine in patients with supraventricular tachycardia

Background-We correlated the electrophysiologic (EP) effects of adenosine w ith tachycardia mechanisms in patients with supraventricular tachycardias ( SVT). Methods and Results-Adenosine was administered to 229 patients with SVTs du ring EP study: atrioventricular (AV) reentry (AVRT; n=59), typical atrioven tricular node reentry (AVNRT; n=82), atypical AVNRT (n=13), permanent junct ional reciprocating tachycardia (PJRT; n=12), atrial tachycardia (AT; n=53) , and inappropriate sinus tachycardia (IST; n=10). There was no difference in incidence of tachycardia termination at the AV node in AVRT (85%) versus AVNRT (86%) after adenosine, but patients with AVRT showed increases in th e ventriculoatrial (VA) intervals (13%) compared with typical AVNRT (0%), P <0.005. Changes in atrial, AV, or VA intervals after adenosine did not pred ict the mode of termination of long R-P tachycardias. For patients with AT, there was no correlation with location of the atrial focus and adenosine r esponse. AV block after adenosine was only observed in AT patients (27%) or IST (30%). Patients with IST showed atrial cycle length increases after ad enosine (P<0.05) with little change in activation sequence. The incidence o f atrial fibrillation after adenosine was higher for those with AVRT (15%) compared with typical AVNRT (0%) P<0.001, or atypical AVNRT (0%) but simila r to those with AT (11%) and PJRT (17%). Conclusions-The EP response to adenosine proved of limited value to identif y the location of AT or SVT mechanisms. Features favoring AT were the prese nce of AV block or marked shortening of atrial cycle length before tachycar dia suppression. Atrial fibrillation was more common after adenosine in pat ients with AVRT, PJRT, or AT. Patients with IST showed increases in cycle l ength with little change in atrial activation sequence after adenosine.