Association Between Blood Urea Nitrogen to Creatinine Ratio and in-hospital Mortality Among Patients With Acute Myocardial Infarction- A Retrospective Cohort Study

Purpose: This study aimed to determine the association between blood urea nitrogen (BUN) and creatinine(Cr) ratio and in-hospital mortality in patients with acute myocardial infarction(AMI). Patients and Methods: This retrospective cohort study included adult patients (≥18 years of age) who were admitted to the intensive care unit (ICU) with a primary diagnosis of AMI were enrolled. Their data were collected from the eICU Collaborative Research Database (eICU-CRD) throughout the continental USA. The data collected from the database included demographic data, vital signs, laboratory test data, and comorbidities. The clinical endpoint was in-hospital mortality. The Cox proportional hazards model was used to evaluate the prognostic values of the basic BUN/Cr ratio, and the Kaplan–Meier method was used to plot survival curves. Subgroup analyses were performed to measure mortality across various subgroups. Results: : In total, 3,831 eligible patients were included. In the multivariate analysis, after being adjusted for age, sex, and ethnicity, the BUN/Cr ratio was found to be a significant risk predictor of in-hospital mortality. The nonlinear relationship between the BUN/Cr ratio and in-hospital mortality was explored in a dose-dependent manner with an apparent inflection point of 18. Furthermore, after adjusting for more confounding factors, the BUN/Cr ratio remained a significant predictor of in-hospital mortality (tertile 3 vs.tertile 1: hazard ratio 2.14; 95% confidence interval 1.16-3.97; p<0.05).The Kaplan–Meier curve for tertiles of the BUN/Cr ratio indicated that survival rates were highest and lowest when the BUN/Cr ratio was ≤15.12 and ≥19.41, respectively, after adjustment for age, sex, and ethnicity(p<0.001). Conclusion: Our findings showed that a higher BUN/Cr ratio was associated with an increased risk of in-hospital mortality in patients with AMI. These results support a revision of how we predict the prognosis of patients with AMI.