Mitral isthmus reconnections in the distant period
Nakashima et al. recently demonstrated that the proportion of patients with MI reconnection was lower in the EIVOM/RF than that of the RF group (37% [13/35] vs. 67% [31/46]).19 Given the fact that all patients received ablation inside the CS before EIVOM in this study, the durability of the MI block in the EIVOM/RF group might be improved. However, the acute and long-term success rate of the RF group was significantly lower (acute 63.6%, long-term 32.6%) compared to that of our study. In our cases, all patients underwent RF ablation under general anesthesia to gain a stable contact force. It was possible to achieve high success rate in the RF group during the procedure.
Reconnections in only the VOM were observed in five patients of the RF group; one of them was MAF using the VOM. EIVOM terminated the MAF and recreated a simultaneous MI line block. Meanwhile, there were no reconnections of the VOM in the EIVOM/RF group, which may offer an advantage in that EIVOM prevented subsequent MAF after AF ablations, as the previous study reported.14
We used AdvisorTM HD grid-mapping catheter to evaluate the left atrial LVA and the effect of EIVOM. The potential is maximized when used in conjunction with the Best Duplicate algorithm of EnSite PrescisionTM. Accurate evaluation of the left atrial LVA is feasible.20 It showed that the effect of EIVOM appeared immediately and was maintained throughout the procedure. Despite of its efficacy, endocardium reconnections were observed in 21/43 (48%) patients of the EIVOM/RF group, which was higher than 29/80 (36%) of the patients in the RF group. This finding suggests that the effect of EIVOM is reversible. Stunned myocardium of the MI area tend to regain conductivity as time progressed.
EIVOM as an adjunctive therapy was observed to have a high clinical success rate during the procedure without excess RF application, which leads to steam pop and cardiac tamponade. There was no parameter that could predict the reconnection of the MI in this study.