Pseudo VA Linking With Atrial Overdrive Pacing

Abstract

I read with interest the recent case report by Leventopoulos et al. 1 published in the Journal of Cardiovascular Electrophysiology. For the differential diagnosis, they performed atrial overdrive pacing (AOP) during macroreentrant atrial tachycardia (AT) with 1:1 AV relationship from the high right atrial septum (HRAS) and proximal coronary sinus (PCS). When AOP was done from the HRAS, the last entrained ventricular beat was the second one after the last stimulus, because of a marked intra-atrial conduction delay due to prior atrial surgery. In their study, the post-pacing VA intervals among different pacing sites (HRAS and PCS) were nearly equal, suggesting the presence of VA linking. 2In general, VA linking indicates AV nodal reentry or AV reciprocating tachycardia, but excludes AT. They measured the interval from the last entrained ventricular beat to the next atrial beat (i.e., the second atrial beat after the last stimulus) as the post-pacing VA interval from the HRAS. However, this measurement seems incorrect from the theoretical point of view. If true VA linking had been present, the first atrial beat after AOP should have occurred following the last entrained ventricular beat, since atrial beats cannot be dissociated from the previous ventricular beats when VA linking exists. In the absence of VA linking (i.e., AT), the timing of the first atrial beat after AOP depends on the distance between the tachycardia origin and pacing site, atrial conduction properties, and mode of the resetting response of the tachycardia, but not on the ventricular activation. Therefore, the post-pacing VA interval should be measured from the last entrained ventricular beat to the first atrial beat after AOP.2 In this case, the post-pacing VA interval becomes a negative value after AOP from the HRAS, indicating the absence of VA linking that is consistent with AT. When AOP was performed from the PCS, however, an AV delay during AOP was small and incidentally close to the difference between the post-pacing interval and tachycardia cycle length. This resulted in similar values of post-pacing VA interval and tachycardia VA interval, which is considered as a conventional criterion of VA linking. Thus, AOP from a single site can be misleading, and this case highlights the importance of the pacing site and careful determination of the last entrained ventricular beat for correct analysis of VA linking by AOP.

Atrial Overdrive Pacing: Is VA Linking Present?

“…We thank Dr. Maruyama for expressing an interest in our article . We believe that the mechanism is scar‐related macrore‐entry atrial tachycardia with a very slow antegrade limb from septal RA to CS 9,10 and fast retrograde limb in the reverse direction (Supporting Fig.…”