Determinants of simultaneous fast and slow pathway conduction in patients with dual atrioventricular nodal pathways

Premature Beats and Unexpected Heart Block

“…Patients with dual AV nodal response should have unidirectional retrograde conduction block in the slow pathway to prevent retrograde invasion from fast pathway conduction. 2 This can be inferred if ventricular pacing with retrograde fast pathway conduction at slow cycle lengths induces AV nodal echo beats or AVNRT.…”

Nonreentrant atrioventricular nodal tachycardia due to triple nodal pathways manifested by radiofrequency ablation at coronary sinus ostium

“…In general, the slow pathway conduction time is markedly prolonged. It was reported that VA conduction was weak or absent in patients with DVR [4,6,8]. Lin et al [6] speculated that blockade of the retrograde slow pathway conduction via fast pathway activation is required for DVR.…”

“…It was reported that VA conduction was weak or absent in patients with DVR [4,6,8]. Lin et al [6] speculated that blockade of the retrograde slow pathway conduction via fast pathway activation is required for DVR. Consistently, in the present case, AV conduction time through the slow pathway was prolonged during the tachycardia ( Figs 3A and 3B) and the VA conduction presumably via the slow pathway was only intermittently observed (Fig.…”

Atrioventricular Nodal Re-Entrant Tachycardia with Two Functionally Discrete Fast Pathways

“…4, incremental ventricular pacing supported the existence of this second fast pathway, which is characterized by a VA interval slightly longer than that of retrograde usual fast pathway conduction and the earliest activation site inscribed at the ostium of the coronary sinus. Additional factors in the inability of ventricular extra-stimuli to penetrate the re-entry circuit orthodromically or anti-dromically might be an anti-dromic unidirectional block in the distal slow pathway, which is one of the major determinants of double ventricular responses, 13,14 and localization of the re-entry circuit to be infranodal. 15 Bundle of His pre-excitation by a single atrial extra-stimulus during the slow-fast form of AVNRT was previously reported in several cases.…”