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. Author manuscript; available in PMC: 2021 Dec 1.
Published in final edited form as: J Thorac Cardiovasc Surg. 2020 Apr 5;162(6):1755–1756. doi: 10.1016/j.jtcvs.2020.03.063

To BIMA or Not to BIMA, that should be the question…rather than how to BIMA.

Thomas A Schwann 1, Mario FL Gaudino 2
PMCID: PMC7869016  NIHMSID: NIHMS1663617  PMID: 32475505

Central Message:

BIMA grafting will remain a niche, rather than a routine, procedure pending convincing randomized data.

Observational studies uniformly report the benefits of bilateral internal mammary artery (BIMA) grafting1,2, yet the only randomized trial did not corroborate these benefits3. Not surprisingly, there is skepticism regarding BIMA grafting and its adoption remains below 5% among CABG patients4. Marzouk et al5 compare outcomes between patients whose second IMA was either used situ (is-BIMA) or as a free (f-BIMA) graft. Among highly selected (12% of entire CABG population) young and healthy patients, 2,464 (95%) is-BIMA and 136 (5%) f-BIMA patients were compared. The authors found that f-BIMA was associated with significantly increased risk of long term mortality but with similar hospital readmission and repeat revascularization rates. Significantly, despite the young age and absence of comorbidities, the mediastinitis rate was disturbingly high (2.5% vs 1.08% in the STS Database6).

The results have to be considered cautiously despite the commendable statistical risk adjustment. The investigators postulate that the increased f-BIMA mortality risk maybe due to a higher failure rate of the f-BIMA versus is-BIMA. This is difficult to reconcile without an increased hospitalization or repeat revascularization rates which would be expected if worse f-BIMA durability was the culprit. To overcome this, they further hypothesize that the free-BIMA failure results in sudden cardiac death. That seems implausible given the findings of the PREVENT IV7 trial in which graft failure was associated with increased repeat revascularization rates, but not mortality. Moreover, a number of reports document excellent free IMA patency8,9. Thus, we are left without a credible basis for the main finding of the study.

This study is unlikely to change surgeons’ practice patterns or impact their views of BIMA grafting. To move the BIMA utilization needle will require convincing randomized data and the only such trial10 is years away. Short of that, BIMA grafting is likely to remain a niche technique (as it was in this study) rather than the standard of care. Gone are the days when a single retrospective study could transition the standard of care as did Loop’s seminal study which almost single handedly moved our field to LIMA based CABG11. For the BIMA enthusiasts there is little in the current study to doubt the orthodoxy that not using BIMA unnecessarily deprives patients of enhanced survival. Although a 2.5% rate of mediastinitis, a “Never Event”, seems high this is consistent with the overwhelming majority of other BIMA reports3. The BIMA believers will counter that the risk of mediastinitis can be mitigated by experience and skeletonization and thus are not an insurmountable impediment to its use. Conversely, BIMA skeptics will most certainly point to this increased risk of mediastinitis is a mortal flaw. They will also rightfully point out that this study offers no compelling reasons to consider the BIMA strategy preferentially over the current LIMA/SVG approach.

Despite the excellent outcomes and intentions of this study, it does not settle the BIMA controversy and we will certainly continue to see future BIMA reports which will perpetuate the current debate but will almost certainly not increase its utilization rate.

Central Picture:

Central Picture:

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To BIMA or not to BIMA.

References:

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