Additional Value of Entrainment Mapping in Complex A
Entrainment mapping is a pivotal electrophysiological approach in
identifying the reentrant mechanism as well as localizing the critical
isthmus for ablation(18). With the evolution of high-density LAT
mapping, not only simple reentrant circuits but also complex circuits
can be confirmed particularly in the setting of abnormal atrial anatomy,
scarring area and multiple circuits, which may reduce dependence on EM.
However, because of the inherent limitations of activation mapping
mentioned above, EM still has an irreplaceable role in identifying
mechanisms of arrhythmias. A study on complex left AT by Strisciuglio et
al. showed that EM with concomitant high-density left AT mapping
significantly improved diagnostic accuracy compared with high-density
left AT mapping alone, particularly in microreentries(19). Another study
comparing high-resolution mapping with EM in interpretation of right
atrial flutter circuits reported a 100% correlation between activation
mapping and EM for CTI upper loop reentrant circuits, and of only 30%
for lower loop reentrant circuits; there was no correlation for lateral
wall reentry, and EM confirmed only 17 of the 27 (63%) circuits
visualized on the LAT map as indeed being active reentry(20). Our study
also demonstrated that ripple mapping combined with EM significantly
improved diagnostic yield of AT mechanisms compared with ripple mapping
alone, especially in patients with Cox-MAZE procedure. A randomized
clinical study by Luther et al. reported that combination of EM and
ripple mapping significantly increased success rate of ablation, with
patients in ripple mapping group undergoing less EM than those in LAT
group(17).
Although EM is not without its limitations, including change or
termination of AT, noncapture, and pacing latency in areas of low
voltage, EM remains a powerful tool to confirm visual reentrant circuit
and corroborate interpretation of eletroanatomical map obtained by
high-resolution mapping, either with ripple mapping or LAT mapping.