Association between the blood urea nitrogen to creatinine ratio and in‑hospital mortality among patients with acute myocardial infarction: A retrospective cohort study

The present study aimed to determine the association between the blood urea nitrogen (BUN) and creatinine (Cr) ratio and in-hospital mortality in patients with acute myocardial infarction (AMI). The present 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. Medical records were obtained from the electronic ICU collaborative research database, which includes data from throughout continental USA. Data included demographic characteristics, vital signs, laboratory tests 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. In total, 5,965 eligible patients were included. In the Cox regression analysis, after being adjusted for age, sex, ethnicity and other confounding factors, the BUN/Cr ratio was found to be a significant risk predictor of in-hospital mortality. There was a non-linear relationship between the BUN/Cr ratio and in-hospital mortality after adjusting for potential confounders. A two-piecewise regression model was used to obtain a threshold inflection point value of 18. Furthermore, after adjusting for additional confounding factors (age, sex, ethnicity, BMI, heart rate, oxygen saturation, platelets, total protein, AMI category, heart failure, history of diabetes, history of hypertension, percutaneous coronary intervention, and administration of norepinephrine, dopamine and epinephrine), the BUN/Cr ratio remained a significant predictor of in-hospital mortality (third vs. first tertile: Hazard ratio, 1.50; 95% CI, 1.08-2.09; P<0.05). The Kaplan-Meier curve for tertiles of the BUN/Cr ratio indicated that in-hospital mortality rates were highest when the BUN/Cr ratio was ≥18.34 after adjustment for age, sex and ethnicity (P<0.05). The present findings demonstrated that a higher BUN/Cr ratio was associated with an increased risk of in-hospital mortality in patients with non-ST-segment elevation myocardial infarction. These results support a revision of how the prognosis of patients with AMI is predicted.