Unveiling a J-shaped association between the triglyceride-glucose index and in-hospital major adverse cardiovascular events in patients with acute myocardial infarction: a retrospective cohort study of 1,065 patients.

Objective: This study was designed to investigate the dose-response relationship between the triglyceride-glucose (TyG) index and the occurrence of in-hospital major adverse cardiovascular events (MACE) in patients with acute myocardial infarction (AMI), and to examine whether a nonlinear association pattern exists. Methods: This single-center retrospective cohort study consecutively enrolled 1,065 patients diagnosed with type 1 AMI who underwent coronary angiography at the Department of Cardiology, The Second Affiliated Hospital of Shenyang Medical College, between June 2022 and June 2025. Baseline data were collected from the electronic medical record system, and the TyG index was calculated using the formula: TyG = Ln [triglycerides (mg/dL) × fasting plasma glucose (mg/dL)]/2. The primary outcome was in-hospital MACE (occurring during hospitalization, ≤7 days after admission), which was a composite of all-cause mortality, acute heart failure, malignant arrhythmia, recurrent myocardial infarction, and cardiogenic shock. Patients were categorized into three groups [T1 [low], T2 [medium], and T3 [high]] based on the overall tertiles of the TyG index. Multivariable logistic regression analysis was employed to construct hierarchical models (a base model, a parsimonious model, and a core model) and to analyze the association between TyG index groups and MACE. Model performance was evaluated by assessing discrimination (area under the curve, AUC), calibration, and clinical utility. Restricted cubic splines (RCS) were used to explore the potential nonlinear relationship between the TyG index (as a continuous variable) and MACE. The inflection point was identified, and piecewise regression analysis was performed. Subgroup analyses were conducted to assess the heterogeneity of the association. Results: This study included 1,065 patients with AMI, who were stratified into T1 (low, Conclusion: This study demonstrates a significant J-shaped nonlinear association between the TyG index and the risk of in-hospital MACE, with an identified inflection point at 9.05. Notably, patients with a medium TyG level (T2 group) exhibited the highest MACE risk, which was significantly greater than that of patients with a low TyG level (T1 group). This finding challenges the conventional linear perception that a higher TyG index consistently correlates with greater risk. The core model incorporating TyG index stratification significantly improved the predictive performance for MACE. These findings collectively underscore the importance of considering the nonlinear effect of the TyG index in risk assessment for AMI patients, suggesting that individuals with medium TyG levels may represent a specific high-risk subgroup warranting particular attention.