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.