Characterization of atrioventricular nodal reentry with continuous atrioventricular node conduction curve by double atrial extrastimulation

Background-Characterization of typical atrioventricular nodal reentrant tac hycardia (AVNRT) with continuous AVN conduction (A(1)A(2)/A(2)H(2)) curves by double atrial extrastimulation (A(1)A(2)A(3)) has never been systematica lly studied. Methods and Results-This study was composed of 33 patients with typical AVN RT and continuous AVN conduction curves (group 1) and 103 patients with AVN RT and discontinuous AVN conduction curves (group 2), Using A(1)A(2)A(3) wi th predefined fast pathway-conducted A(2), we examined the effects of slow pathway ablation on the A(2)A(3)/A(3)H(3) curves in both groups. In group 1 , anterograde AVN effective refractory period (272+/-33 versus 277+/-47 ms, P>0.05) and AVN Wenckebach block cycle length (320+/-45 versus 343+/-59 ms , P>0.05) remained unchanged after ablation. A(2)H(2)max was shorter in gro up 1 than group 2 (237+/-89 versus 395+/-72 ms, P<0.05) at baseline. It sho rtened in group 2 (395+/-72 versus 221+/-78 ms, P<0.001) but remained uncha nged in group 1 (237+/-89 versus 214+/-59 ms, P>0.05) after ablation. A(1)A (2)A(3) could further disclose discontinuous A(2)A(3)/A(3)H(3) curves in 29 patients of group 1. A(3)H(3)max shortened in both groups (375+/-81 versus 238+/-82 ms, P<0.001, and 419+/-104 versus 220+/-78 ms, P<0.001, respectiv ely) in a similar fashion. Successful ablation resulted in loss of the left portion of the A(2)A(3)/A(3)H(3) curves in the 4 patients of group 1 with continuous A(2)A(3)/A(3)H(3) curves. Conclusions-Use of A(1)A(2)A(3) could expose discontinuous A(2)A(3)/A(3)H(3 ) curves in most patients with continuous A(1)A(2)/A(2)H(2) curves. Signifi cant shortening of A(3)H(3)max after ablation may be indicative of successf ul elimination of AVNRT.