Retrograde atrial activation via the slow AV nodal pathway caused proximal coronary sinus activation to precede low septal right atrium activation by 5-20 msec.
Observational (n=7)
The slow AV nodal pathway has a distinct retrograde exit that alters atrial activation sequences, highlighting the need for caution when differentiating normal AV node conduction from anomalous bypass tracts during tachyarrhythmias.
To characterize the sequence of retrograde atrial activation in the presence of dual atrioventricular (AV) nodal pathways, we analyzed electrophysiologic data from seven patients in whom discontinuous AV nodal and ventriculoatrial conduction curves could be induced with programmed electrical stimulation. In all patients, electrograms of the high right atrium (HRA), lateral right atrium (LRA), low septal right atrium (SRA) and proximal coronary sinus (PCS) near the coronary sinus ostium were simultaneously recorded at a paper speed of 150-250 mm/sec. During programmed ventricular extrastimulation and incremental ventricular pacing, ventriculoatrial conduction via the fast AV nodal pathway resulted in SRA activation before PCS, HRA and LRA activation. However, the sequence of retrograde atrial activation abruptly changed with a shift from retrograde fast to retrograde slow AV nodal pathway conduction. Characteristically, during ventriculoatrial conduction via the slow AV nodal pathway, activation of the PCS preceded SRA activation by 5-20 msec and was accompanied by an alteration of the temporal relationship between HRA and LRA activation in all patients. These observations suggest that anatomically, the proximal common AV nodal pathway is a broad area that permits the slow AV nodal pathway to have a retrograde exit located posteriorly, inferiorly and to the left of that of the fast AV nodal pathway, and that the retrograde atrial activation sequence recorded during tachyarrhythmias should be determined with caution attempting to differentiate retrograde normal AV pathway from retrograde anomalous bypass tract conduction.
Sung et al. (1981) conducted an observational in Dual atrioventricular nodal pathways (n=7). Programmed electrical stimulation vs. Fast vs slow AV nodal pathway conduction was evaluated on Sequence of retrograde atrial activation. Retrograde atrial activation via the slow AV nodal pathway caused proximal coronary sinus activation to precede low septal right atrium activation by 5-20 msec.