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.