INDUCTION OF ATRIOVENTRICULAR NODE REENTRANT TACHYCARDIA WITH ADENOSINE - DIFFERENTIAL EFFECT OF ADENOSINE ON FAST AND SLOW ATRIOVENTRICULAR NODE PATHWAYS

Objectives. This study sought to evaluate the sensitivity of fast and slow atrioventricular (AV) node pathways to incremental doses of adeno sine in patients with typical AV node reentrant tachycardia. Backgroun d. Although adenosine is known to depress conduction through the AV no de, the relative sensitivity to adenosine of the anterograde fast and slow pathways in patients with dual AV node pathways and typical AV no de reentrant tachycardia has not previously been studied. Methods. Six teen patients with dual AV node physiology and typical AV node reentra nt tachycardia and 10 control patients were given incremental doses of adenosine during atrial pacing. Results. In 14 of 16 patients with du al-AV node physiology, administration of small doses of adenosine duri ng atrial pacing led consistently to transient block of impulse conduc tion in the fast pathway before block in the slow pathway, resulting i n abrupt prolongation of the AH interval with continued 1:1 AV conduct ion, The mean (+/-SD) doses of adenosine required to cause conduction block in the fast and slow pathways were 2.7 +/- 3.0 and 7.2 +/- 4.7 m g, respectively (p = 0.001), In 9 of 16 patients, administration of lo w dose adenosine led to initiation of AV node reentrant tachycardia, T he control patients showed no abrupt increases in AH interval with adm inistration of adenosine during atrial pacing. Conclusions. In most pa tients with dual AV node pathways and typical AV node reentrant tachyc ardia, the fast pathway is more sensitive than the slow pathway to the effects of adenosine. (C) 1997 by the American College of Cardiology.