ABSTRACT
OBJECTIVES: Refractory period and conduction time of the slow and fast pathways in the atrioven-tricular node are known to be the most important determinant of the inducibility of atrioventricular nodal reentrant tachycardia (AUNRT) but their relationship has not been determined in Korean. METHODS: Two hundred and ten patients under-gone electrophysioiogic study. One hundred twenty two patients with dual AV nodal pathways were divided into two groups (group I, 77 patients with no inducible AVNRT; group II, 45 patients with inducible AVNRT). RESULTS: Antegrade dual AV nodal pathways were documented in 77 patients (47%) out of 165 patients on whom AVNRT was not induced, Antegrade ERP of slow pathway in paced rhythm (600 msec) was shorter in group II than in group I (331 +/- 14 msec vs 269 +/- 47 msec, p<0.05). Ventriculoatrial block cycle length (VABCL) and retrograde ERP of the AV conduction system were significantly shorter in group 2 than in group 1 (p<0.001). Maximum slow pathway conduction times in sinus rhythm and paced rhythm (600msec) in group 2 were significantly longer than in group 1 (sinus rhythm: 332 +/- 68msec vs. 379 +/- 88msec, p<0.005; paced rhythm: 332 +/- 69msec vs. 392 +/- 85msec, p<0.005). The ERP gaps of two AV nodal pathways of group 2 in sinus rhythm and in paced rhythm were also significantly longer than those of group 1 (sinus rhythm 41 +/- 3msec vs. 78 +/- 50msec, p<0.001; paced rhythm 36 +/- 32 msec vs. 72 +/- 19msec, p<0.005). The incidence of intact ventriculoatrial conduction was significantly higher in group 2 than in group 1 (p<0.05). Antegrade slow pathway conduction time (A2H2 interval) at the time of AVNRT induction with single atrial premature depolarization (APD) with a coupling interval over 10 msec less than that of an APD producing AH jump were not correlated with VABCL (r=0.193, p<0.05). CONCLUSION: Dual AV nodal pathways were observed in 47% of patients with no-inducible AVNRT group. The inducibility of AVNRT appears to be closely ralated to the some conduction characteristics of the dual pathways and the refractoriness, i.e. maximum slow pathway conduction time, the ERP gap of two pathways, retrograde fast pathway ERP, VABCL.