DISCUSSION
The present study indicated that the use of
2nd-arterial conduit might be associated with superior
long-term survival in patients following CABG. On the other hand, RA
when compared to RITA as a 2nd arterial conduit had a
similar long-term outcome.
The use of multiple arterial grafts has been extensively studied over
the past decade. Several observational studies as well as meta-analyses
reported a survival benefit when RITA or RA is used as second arterial
graft4-8. Yet, the adoption rate of multiple arterial
grafting ranges between 4% to 32%5,9-10. Despite the
reported benefit of the arterial grafts, ART found no survival benefit
in the intention-to-treat analysis at 10-years between BITA and
SITA11. Parasca et al. in a study from the SYNTAX
trial and registry found no survival benefit at 5–years follow-up in
patients with second arterial vs venous graft10.
However, Chikwe and colleagues in a 3588-propensity matched
multi-arterial and single-arterial CABG study, reported that multiple
arterial CABG was associated with reduced long-term mortality as well as
MI and reintervention rate21 on the other hand,
controversy still remain on whether RA has similar long-term benefits as
RITA. Schwan et al. in a multicenter study reported equally improved
long-term survival when RITA or RA was used22. Whereas
Shi et al.23 and Benedetto et al.24reported significant survival benefit from RITA when compared to RA. On
the contrary, the recent results of the 10-years RAPCO
trials25, showed that the 10-year patency rate of the
RA is significantly higher than that of the free RITA and better than
that of the vein graft, whereas long-term survival was improved when RA
was compared to free RITA but not when RA was compared to vein graft. It
should be noted that in the RAPCO trial, RITA was used as free graft
directly connected to the aorta and the possible caliber mismatch
between them could affect and reduce the patency of the RITA graft.
Therefore, this uncertain and controversial long-term results in
addition to increased risk of DSWI and the perceived technical
complexity when using multiple arterial grafts lead to inconclusive
results on whether the use of second arterial graft is safe and
associated with improved short- and long-term outcomes.
By conducting our PS-matched study based on 695-pairs of patients
receiving 2nd-arterial graft vs SITA+Vein we found
that the use of the 2nd-arterial graft is associated
with improved survival. On the other hand RA and RITA as second arterial
conduit had comparable long-term mortality before as well as after PS
matching. Recent meta-analysis performed by Gaudino et al. supported our
findings. However, they also showed that the use of RITA was associated
with increased risk of DSWI but not when RA was
used8,11. In our study there was no difference between
2nd-arterial graft vs SITA+Vein in terms of DSWI nor
it was between RITA and RA. This was probably due to the fact that
approximately 70%(67.6%) of the patients in the 2ndarterial graft group had skeletonized ITA’s and it was showed in the sub
study of ART as well as in the recent meta-analysis, that with a
skeletonization technique, the risk of sternal wound complication with
BITA is similar to that after standard pedicled SITA
harvesting8,26.
On the other hand, IR following patients undergoing CABG is not a rare
phenomenon and is associated with increased long-term mortality as
reported by Garcia et al.27. In the present study we
analyzed multivariable predictors of late all-cause mortality in the
2nd-arterial conduit group vs SITA+Vein and in the
2nd-arterial conduit group(RA vs RITA). In the whole
cohort, IR was a significant independent predictor of late
mortality(HR:1.25;95%CI;1.13-1.39;p<0.001). However, this was
not the case in the subgroup of 2nd-arterial graft
(RITA vs RA)(HR:1.46;95% CI;0.96-2.24;p=0.07). Therefore IR in patients
with multiple arterial grafts may not have a negative impact on
long-term survival in patients following CABG.
The present study has several limitations. The main limitation is the
lack of randomization. In order to limit inherent risks of potential
selection bias a propensity score matching procedure was performed.
Secondly, no data were available with respect to cause of death, need
for repeated revascularization or graft patency. Thirdly, the power of
the study to detect differences in survival among RITA and RA is very
small, because of the small sample size. Finally, due to small number of
patients in the RA group we did not analyze outcomes of different
conduits with respect to the grafted territory.