Abstract / Summary
Abstract Background The triglyceride-glucose (TyG) index and stress hyperglycaemia ratio (SHR) are validated surrogate markers of insulin resistance and acute glycaemic stress, respectively. Whether these biomarkers predict outcomes after cardiac surgery has not been previously systematically synthesised. This review evaluated the association between TyG index and/or SHR and postoperative outcomes in adults who underwent cardiac surgery. Methods This systematic review followed the PRISMA 2020 guidelines and was prospectively registered withPROSPERO (CRD42026144643). We searched PubMed, Embase, Cochrane Library (CENTRAL), Web of Science, and Scopus from inception to 20 August 2026 for cohort, case-control, and cross-sectional studies reporting the association between TyG index and/or SHR and postoperative outcomes in adults who underwent cardiac surgery. Two reviewers independently screened the records and extracted the data in duplicate, with disagreements resolved by discussion. Risk of bias was assessed using the Quality in Prognosis Studies (QUIPS) tool, and certainty of evidence was rated using GRADE. Results The search identified 957 records; after the removal of 526 duplicates, 431 titles and abstracts were screened, of which 34 reports underwent full-text review. Twenty-four studies met the inclusion criteria, and ten were excluded forreasons reported in full. The included studies evaluated outcomes predominantly after coronary artery bypass grafting (CABG), with single studies in septal myectomy and off-pump CABG populations combined with adiposity indices. Elevated TyG index and/or SHR were associated with an increased risk of all-cause mortality, major adverse cardiovascular events (MACE), major adverse cardiovascular and cerebrovascular events (MACCE), acute kidney injury (AKI), new-onset postoperative atrial fibrillation, and postoperative stroke in most of the included studies. However, this association was not uniform; two large cohorts ( n = 18,307 and n = 16,440) identified U-shaped rather than monotonic relationships with perioperative and in-hospital outcomes, and one study found no significant association between the TyG index and AKI in a chronic kidney disease subgroup. Several studies have drawn on the MIMIC-IV database, raising the possibility of patient-level overlap that could not be fully excluded. The risk of bias was predominantly moderate to high, driven chiefly by retrospective single- or dual-centre designs and residual confounding. The certainty of evidence was low to very low across all outcomes, downgraded principally for risk of bias, inconsistency and imprecision. Conclusions The TyG index and SHR are associated with adverse outcomes after cardiac surgery, chiefly CABG; however, the association is not uniformly monotonic, the evidence base is heterogeneous and overlapping in the data source, and the certainty of evidence is low to very low. These biomarkers may hold promise as low-cost adjuncts to perioperative risk stratification; however, current evidence does not support routine clinical use without further prospective multicentre validation that addresses cohort overlap and reports outcomes with full event-level transparency.