Discussion
This study focused on how gaps formed by Maze procedure affect AF and AT, and to our best knowledge, this focus has never been before. Since the places where gaps are likely to occur have been clarified, it is possible to understand the places where care must be taken to prevent gaps during Maze procedure, and this caution may reduce the recurrence rate of AT and AF. In addition, understanding the difficult-to-treat gaps before catheter ablation may be making it easier to plan treatment.
The main findings of this study were that the distribution of gaps was mainly on the LA and macroreentrant-ATs also occurred mainly on the LA. Previous studies reported that about two-thirds of macroreentrant-ATs after the Maze procedure occurred on the LA.17-19 Our results are similar to previous reports. Of the left-side macroreentrant-ATs, most of the cases were M-AFL and were almost gap-related. In Huo’s report,17 the incidence of M-AFL in the left-side ATs was about 60%, while in our study, a slightly higher incidence of 78.6% was found. It has been said that M-AFL catheter ablation was challenging because of convective cooling as a result of coronary sinus blood flow and the thickness of the LA near the mitral valve annulus (MVA).20 In our cases, 1 of 22 M-AFL cases (4.5%) failed to be treated at first session, and combination of chemical and RF ablation worked effectively at second session. Although, this study indicated that the gap-related ATs were predominant, but there were some non-gap-related AT. It is conceivable that the arrhythmogenic substrate may have been formed due to the possibility of surgical injury or the load such as ischemia or valvular disease.
Gopinathannair et al. reported that the second common left-side ATs was the roof dependent AFL,13 but in our study, there was no case of roof dependent AFL. The reason might be due to that either the roof line or the bottom line in any type of Maze procedure was completed in our study. Additionally, they reported 18% of PV gap-related ATs were induced. However, in our study, there were only 2 PV gap-related ATs among all 49 mappable ATs (4.1%). The 2 PV gap-related reentrant ATs were observed in Kosakai’s Maze and Maze Ⅲ cases, indicating cut-and-sew method also could make untransmural lesions that may cause PV gap-related AT.
As previously reported, the number of ATs induced per case was 1.09±0.35,13 whereas, in our study, it was 1.6±0.8 per case. This incidence may be slightly high. Three or more ATs were induced in patient numbers 7, 8, 21, 25, 27, 28. Patient 7, 21, and 25 underwent the Maze procedure with cryo energy, patient 8 with RF energy, and patient 27 and 28 underwent the Maze procedure with cut-and-sew method. AT and AF may occur due to untransmural lesions that are created in CA or the Maze procedure.21, 22 Although, Winkle et al reported that compared to the non-cut-and-sew method, the cut-and-sew Maze procedures can form a transmural lesion and result in fewer gaps,15 but there are no significant difference of the relationship between gaps and Maze procedure in this study. However, the relationship between AF/PV gap related AT incidence and PV gap were significantly related in this study. In other words, PV gap associated with AT and AF as previous report.23, 24 The cut-and-sew technique takes time and effort which may be a burden to the heart,25, 26 in contrast to the Maze with cryo or RF energy. To prevent the recurrence of AF/PV gap related AT, it may be necessary to create transmural lesions surround PV using simpler and faster technique.
CryoMaze in our study were all performed in our institute. As Kakuta reported previously, the Kaplan-Meier analysis showed that the rates of freedom from recurrent AF were 91.9% at 1 year and 86.1% at 5 years.2 Over the course of 4 years, the proportion of arrhythmia-free survival after CA following all Maze procedures about 70% in our study, which was considered similar to that of ordinary AT and AF ablation after Maze procedure.17, 27 These data may indicate the combination of Maze procedure and CA may be an effective for regaining sinus rhythm. No intraoperative and postoperative complications were observed in this study. Although the number of cases may be small, it is possible that severe complications such as cardiac tamponade and perforation may not occur because of pericardial adhesions after CS. These facts indicate that AT and AF after any Maze procedure used in this study can be safely and effectively treated.