Metformin Exposure Associated with Up to 81% Lower 30‑Day Mortality After Cardiac Surgery in T2DM: A Critical Appraisal of AHA 2025 MIMIC‑IV Cohort Findings

Highlights

– A retrospective cohort analysis of 2,694 T2DM patients from the MIMIC‑IV database presented at AHA 2025 reported substantially lower short‑ and long‑term mortality among those with metformin exposure around cardiac surgery (30‑day HR 0.19; 95% CI 0.07–0.54).
– Absolute 30‑day mortality difference was 4.1 percentage points (0.4% vs 4.5%); protective associations persisted at 90 and 360 days and across sensitivity and propensity‑matched analyses.
– Findings are hypothesis‑generating: biologic plausibility exists, but residual confounding, exposure misclassification, and perioperative management variables limit causal inference; randomized trials are needed.

Background and clinical context