Circulation, Vol 68, 23-32, Copyright © 1983 by American Heart Association
R Mahmud, M Lehmann, S Denker, CJ Gilbert and M Akhtar
Patients with DDD pacemakers who have intact retrograde conduction are
known to be at risk of developing ventricular and "endless loop"
tachycardia. To address this problem, a pacing protocol was designed in
which V2A2 conduction was assessed in 16 patients during ventricular pacing
alone (standard method) and during paced atrioventricular (AV) sequential
drive (AV sequential method); the results were then compared. In eight of
16 patients who had intact retrograde conduction with both methods (group
1), the V2A2 intervals were significantly shorter (by 60 to 340 msec) with
the AV sequential method. In the remaining eight patients, who demonstrated
V2A2 block with the standard method, no V2A2 block occurred with the AV
sequential method. In this study, two sets of AV intervals were programmed
to produce collision of the two impulses (atrial and ventricular), either
in the AV node or the His-Purkinje system (HPS). The site of V2A2
facilitation was related to the site of impulse collision. These results
can be explained by earlier excitation by the atrial impulse (of AV node
and/or HPS) during AV sequential pacing. However, in some cases it was
evident that antegrade propagation of the atrial impulse was responsible
for subsequent facilitation. The data suggest that assessment of retrograde
conduction in candidates for DDD pacemakers can be made most accurately by
the AV sequential method.
ARTICLES
Atrioventricular sequential pacing: differential effect on retrograde conduction related to level of impulse collision