Evidence for functionally distinct dual atrial inputs to the human AV node.

Although conventional models of the human atrioventricular (AV) node assume a single upper common pathway, animal studies demonstrate dual atrial inputs: an anterior input from the interatrial septum and a posterior input from the crista terminalis (running near the os of the coronary sinus in the posteroseptal region). We hypothesized that functionally distinct dual atrial inputs to the AV node also exist in humans and that the anterior input has a lower safety factor for impulse propagation. To evaluate this hypothesis, we examined 20 patients undergoing radiofrequency ablation of the slow AV nodal pathway for AV nodal reentrant tachycardia who underwent subsequent follow-up testing. After ablation near the os of the coronary sinus (and posterior to the compact AV node), 11 patients had no residual slow pathway conduction [SP(-)], whereas 9 did [SP(+)]. The effective refractory period of the fast AV nodal pathway (FP-ERP) and anterograde AV nodal Wenckebach (AVN-W) cycle length were significantly increased at follow-up in the SP(-) patients (FP-ERP = 336 +/- 71 vs. 387 +/- 103 ms, P = 0.02; AVN-W cycle length = 356 +/- 74 vs. 442 +/- 118 ms, P = 0.03) but not in SP(+) patients. Similarly among 10 patients undergoing radiofrequency ablation of a right posteroseptal accessory pathway (near the os of the coronary sinus), 5 developed impaired AV conduction: abnormal anterograde pacing-induced AVN-W cycle length in 4 patients and 2:1 AV nodal block in 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)