Bypass failure of internal mammary artery caused by subclavian artery stenosis: its clinical characteristics and cardiovascular outcomes in patients receiving coronary artery bypass graft surgery.

Background: While internal mammary artery (IMA) has become a major conduit of coronary artery bypass graft (CABG) surgery, subclavian artery stenosis (SAS) could cause subsequent coronary events due to ischemia of myocardial territory supplied by IMA. Clinical characteristics and cardiovascular outcomes of SAS-related IMA failure (SAS-IMAF) remain to be fully determined yet. Therefore, the current study was designed to characterize SAS-IMAF in patients receiving CABG with IMA.

Methods: This is a retrospective observational study which analyzed 380 patients who presented acute coronary syndrome/stable ischemic heart disease (ACS/SIHD) after CABG using IMA (2005.01.01-2020.10.31). SAS-IMAF was defined as the presence of myocardial ischemia/necrosis caused by SAS. Clinical characteristics and cardiovascular outcomes [major adverse cardiovascular events (MACE) = cardiac death + non-fatal myocardial infarction + non-fatal ischemic stroke], were compared in subjects with and without SAS-IMAF. Multivariate Cox proportional hazards model and propensity score-matched analyses were used to compare cardiovascular outcomes between those with and without SAS-IMAF.

Results: SAS-IMAF was identified in 5.5% (21/380) of study subjects. Patients with SAS-IMAF are more likely had a history of hemodialysis (P<0.001), stroke (P<0.001) and lower extremity artery disease (P<0.001). Furthermore, SAS-IMAF patients more frequently presented ACS (P=0.002) and required mechanical support (P=0.02). Despite SAS as a culprit lesion causing ACS/SIHD, percutaneous coronary intervention was firstly selected in 47.6% (10/21) of them. Consequently, 33.3% (7/21) of SAS-IMAF patients required additional revascularization procedure ( 0.3%, P<0.001). During 4.9-year observational period, SAS-IMAF exhibited a 5.82-fold [95% confidence interval (CI): 2.31-14.65, P<0.001] increased risk of MACE. Multivariate Cox proportional hazards model [hazard ratio (HR) 4.04, 95% CI: 1.44-11.38, P=0.008] and propensity score-matched analyses (HR 2.67, 95% CI: 1.06-6.73, P=0.038) consistently demonstrated the association of SAS-IMAF with MACE.

Conclusions: SAS-IMAF reflects a high-risk phenotype of polyvascular disease, underscoring meticulous evaluation of subclavian artery after CABG using IMA.