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Page 12 of 18 Browne et al. Vessel Plus 2024;8:19 https://dx.doi.org/10.20517/2574-1209.2023.126

MULTIPLE ARTERIAL GRAFTING
Single, multiple, or total arterial grafting
For decades, many surgeons have assumed that using arterial rather than venous conduits would improve
outcomes for patients (i.e., the arterial grafting hypothesis). However, this remains to be proven in
randomized studies. Currently, saphenous veins are most often used as secondary conduits as part of a
single arterial grafting (SAG) strategy. Nevertheless, there is growing interest in using secondary RIMA (i.e.,
bilateral IMA grafting) or radial artery conduits to achieve multiple arterial grafting (MAG) and three or
more arterial conduits with no vein grafts to achieve total arterial grafting (TAG). The proposed advantages
of MAG or TAG over SAG include reductions in the incidence of mortality and major adverse
cardiovascular events over the long term.

Observational studies have generally supported the arterial grafting hypothesis by associating MAG using
secondary RIMA (i.e., bilateral IMA [BIMA]) with improved clinical outcomes compared with secondary
veins (i.e., SAG) [34,59-62] . In a recent analysis of MAG vs. SAG in over one million patients included in the
Society of Thoracic Surgeons Adult Cardiac Surgery Database (STS-ACSD) (2008-2019), MAG was
associated with improved 10-year survival (hazard ratio, 0.86; 95%CI: 0.85-0.88) . Similarly, MAG was
[62]
associated with a lower risk of all-cause mortality in a recent post hoc analysis of 1,466 patients from the
Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery Extended Survival
[63]
(SYNTAXES) study after a lengthy follow-up of 12.6 years . However, support for the hypothesis has not
been demonstrated in a large randomized trial. In the Arterial Revascularization Trial (ART), which aimed
to establish that BIMA was superior to SAG, there were no significant differences in the incidence of all-
cause mortality and the composite of all-cause mortality, myocardial infarction, or stroke in 1,554 patients
who received BIMA or SAG after 5 and 10 years of follow-up [30,64] . One reason for the lack of benefit of
BIMA using RIMA provided by the authors was confounding by radial artery use (radial artery use
improved outcomes for patients preferentially in the SAG group). Given the reports of suboptimal rates of
RIMA graft failure, often comparable to or worse than saphenous veins (e.g. Gaudino et al.,
[6,7]
Yokoyama et al., COMPASS CABG ), an alternative hypothesis has emerged - benefits of BIMA were lost
due to poor RIMA results [4,13,28] . Suboptimal outcomes with RIMA highlight an important limitation of the
common MAG vs. SAG comparison, as it fails to account for the type of secondary arterial conduit used.
Consequently, important heterogeneity (e.g., potential harm) within the MAG group can easily be missed.
However, it is important to note that infrequent use of RIMA often limits separate reporting of RIMA
results (i.e., low statistical power), particularly in randomized surgical studies that are typically much
smaller than administrative database studies. Given the extensive sample size of the STS-ACSD, additional
analyses separately reporting on the use of the RIMA and radial artery for MAG would be a welcomed
contribution to the field.

Underutilization of MAG
Current guidelines recommend (Class 2a, level of evidence B-NR) that BIMA grafting be performed by
experienced operators in appropriate patients to improve long-term cardiac outcomes . However, the use
[10]
of MAG (including BIMA grafting) remains infrequent. For instance, a recent registry study reported that
[62]
most centers in the USA utilize MAG at an annualized rate of less than 5% . Limited adoption is possibly
due to challenges associated with multiple arterial grafting, such as a steep learning curve for surgeons,
lengthier harvesting times, perceived higher risk of sternal wound complications, inconsistent experience
and training in MAG techniques, and conflicting evidence between observational and randomized studies
(e.g., the neutral results of the ART trial). Moreover, in retrospective observational studies, the lack of
sufficient institutional experience in MAG using RIMA is associated with increased operative risk [60,65] ; thus,
likely contributing to hesitancy among institutions and surgeons that infrequently use MAG. The additional
surgical expertise needed in MAG, particularly with RIMA, may also explain reports of suboptimal clinical