GDMT Adherence and Arterial Grafting Strategy: Outcomes in GDMT-Compliant SIMA vs GDMT-Noncompliant BIMA CABG

BACKGROUND: The interaction between conduit strategy and longitudinal guideline-directed medical therapy (GDMT) adherence remains unclear. OBJECTIVES: To compare long-term outcomes between patients who underwent GDMT-compliant single internal mammary artery (SIMA) grafting and GDMT-noncompliant bilateral internal mammary artery (BIMA) grafting in isolated primary coronary artery bypass grafting (CABG). METHODS: Adults ≥18 years of age who underwent isolated CABG with SIMA or BIMA between 2011-2024 were retrospectively analyzed. GDMT compliance was defined as ≥80% medication coverage from discharge to first major adverse cardiovascular event (MACE) or censoring (through last follow-up if no MACE). Patients were restricted to GDMT-compliant SIMA with saphenous vein grafts (cSIMA) versus GDMT-noncompliant BIMA with saphenous vein grafts (ncBIMA). Propensity-score matching (1:4) was performed. The primary endpoint was time to first MACE (all-cause mortality, myocardial infarction (MI), and repeat revascularization). RESULTS: Matching yielded 157 ncBIMA and 618 cSIMA with similar follow-up (8.13 vs 7.62years, p=0.143). ncBIMA more often received ≥3 grafts (87.3 vs 70.6%, p<0.001). Time-to-event analyses demonstrated higher cumulative MACE in cSIMA (5-year 22.5 vs 12.1%; 10-year 39.7 vs 29.1%; log-rank p=0.0394) and higher cumulative incidence of MI hospitalization (Gray's p=0.0096) and revascularization (Gray's p=0.0028). After adjustment for pump status and graft number, cSIMA remained associated with higher hazards of MACE (HR1.54, 95%CI 1.07-2.20), MI hospitalization (HR2.10, 95%CI 1.01-4.36), and revascularization (HR3.01, 95%CI 1.50-6.03). CONCLUSIONS: Despite GDMT compliance, cSIMA was associated with higher long-term MACE than ncBIMA, driven by MI hospitalization and repeat revascularization, supporting broader consideration of BIMA in appropriately selected patients in maximizing survival benefit.