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.