DISCUSSION
Several observational studies and meta-analysis have reported the
survival advantage when using BIMA compared to SIMA, even in diabetics
and elder populations.[1-8] The survival advantage
seems to increase through the postoperative years, even beyond 15
years.[9-10] These studies have also reported
equivalent results in terms of mortality and morbidity after the use of
BIMA when compared to SIMA, therefore raising the question of why the
routine use of BIMA is not standard practice.
Our study confirmed the survival advantage of BIMA compared to SIMA and
the absence of extra complications or in-hospital mortality excess when
the BIMA is used.
The only RCT to date, the Arterial Revascularization Trial (ART), which
reported recently their 10-years results has not been able to
demonstrate a survival benefit with the use of BIMA at one, five or ten
years. Our mortality result using BIMA is significantly lower that the
results reported in the ART trial (1% vs. 2.5% at 1 year and 5% vs.
8.7% at 5 years).[11-13]
They also reported a repeated revascularization rate of 1.8% at
one-year for the BIMA group and 1.3% for the SIMA
group.[11-13] We have demonstrated a lower
repeated revascularization rate, especially at one-year (0.4%), which
is even more impressive if we take on account that we are reporting
OPCAB surgery, which has always had slightly higher rates of reported
repeated revascularization (1.4% at one-year in the CORONARY trial,
4.6% at one-year in the ROOBY trial).[25, 26]
A subanalysis of the ART comparing 5-years outcomes of the two
revascularization strategies used in their trial (ONCAB and OPCAB) did
not demonstrate any significant differences between the two of them.
They report 8% five-year mortality for both strategies, while we
reported an overall 5-year mortality of 10%, significantly higher in
the SIMA group (16% vs. 5%, p <
0.001).[15]
One of the main limitations for the routine use of BIMA has been the
high reported rate of DSWI. In our study, the incidence of DSWI was only
2%. The incidence of sternal reconstruction in our series was only 1%,
lower than the ART study, that reported a 1.9% sternal wound
reconstruction in the BIMA group and 0.6% in the SIMA group at
one-year. Our lower rates are consistent with the lower rates of DSWI
expected for patients undergoing BIMA harvesting in the OPCAB
setting.[11-16]
It has been reported that the skeletonized technique reduces the risk of
DSWI without compromising the long-term graft
patency.[16] The ART trial suggested, that the use
of bilateral skeletonized BIMA has the same risk of DSWI than a pedicle
SIMA.[12] Our strategy for harvesting mammary
arteries consists on semi-skeletonize the LIMA and completely
skeletonize the RIMA.
The optimal configuration of BIMA grafts is unknown. A number of
grafting strategies have been described, including bilateral grafts in
situ, use of the RIMA as a free graft from the aorta and the creation of
T or Y composite grafts from the LIMA. None of them seem to be superior
in terms of survival or long-term patency.[17,18]
In our center, the initial use of free RIMA has declined in favor of the
current strategy of T composite grafts between LIMA and RIMA.
The routine use of BIMA is still very limited. Despite the clear
survival benefit and the equivalent in-hospital complications, it is not
offered to all patients. Some advocated reasons are the technical skills
required for harvesting and grafting, the increased operating time and
resources, the lack of consensus for selection of patients whom can
benefit most and the higher rate of DSWI.
In our institution, we believe that the technical aspects can be taught,
and we include them in our training program. However, the lack of
consensus for selection criteria is important and at present, we only
offer BIMA to certain patients based on the individual surgeon’s own
selection criteria.
The use of the radial artery (RA) is still generating debate. Several
studies had tried to compare it to BIMA. A meta-analysis confirmed the
survival benefit of the BIMA also versus
SIMA-RA.[21] On the other hand, a similar benefit
to BIMA when using a SIMA-RA composite but obviously, eliminating the
extra risk of DSWI has also been recently
reported.[22]
Furthermore, when analyzed as a third arterial conduit, the use of a RA
has not shown to add any survival benefit. [23,
24]
In our study, the radial artery was used only in 20% of the cases,
mostly in the initial years of the study. The current practice of the
author is to use the BIMA for the left-sided lesions and a SV conduit
for the right-sided lesions, reserving RA for when there are no other
conduits available.
Our study has the limitations of being retrospective and purely
descriptive. We report a single surgeon experience with a level of
expertise reflected in a greater number of distal anastomoses and lower
rate of conversion and incomplete revascularization compared to the
historical OPCAB RCTs, but with the uncertainty of the feasibility of
extrapolating these results to other surgical practice.