Blood urea nitrogen to left ventricular ejection fraction ratio: a predictor of in-hospital outcomes in STEMI patients

Background The in-hospital mortality of ST-elevation myocardial infarction (STEMI) remains as high as 4–12%. Heart and kidney are closely linked, and both renal and cardiac function have been confirmed to be associated with the prognosis in patients with STEMI. This study intends to evaluate the prognostic value of blood urea nitrogen (BUN) to left ventricular ejection fraction (LVEF) ratio (BLR) in STEMI patients. Methods From January 2015 to January 2023, 2435 consecutive STEMI patients were enrolled. The primary endpoint was in-hospital all-cause mortality and the second endpoint was major adverse cardiovascular events (MACE) including cardiovascular death, nonfatal stroke, and nonfatal myocardial infarction. The predictive value of BLR was compared with BUN, LVEF, traditional markers and scores (GRACE score and TIMI score) by receiver operating characteristic (ROC) curves, the area under the curve (AUC) were compared by DeLong test. Then patients were divided into two groups based on the cut-off value of BLR determined by Youden index and compared the in-hospital mortality and MACE. The association between BLR and endpoints was investigated by Cox regression. Results Totally 2435 patients were included in our study, among which 90 (3.70%) patients died and 110 (4.52%) MACEs were collected. The non-survivors had significantly higher BUN level and lower LVEF value. The AUCs and DeLong test showed that the predictive value of BLR was significantly higher than BUN, LVEF, creatinine, NT-proBNP, and troponin I but was comparable to GRACE score and TIMI scores. The optimal cut-off value of BLR was 12.54 with a sensitivity of 75.6% and a specificity of 67.6%. The in-hospital mortality and MACE was significantly higher in high BLR group (8.23% vs. 1.37% for in-hospital mortality and 9.44% vs. 1.99% for in-hospital MACE, all p < 0.001). After multivariable adjustment, BLR ≥ 12.54 was still independently associated with higher in-hospital mortality (HR = 1.948, 95%CI 1.143, 3.318, p = 0.014) and MACE (HR = 1.720, 95%CI 1.066, 2.774, p = 0.026). Conclusion BLR is an important prognostic index to identify patients at high risk of in-hospital prognosis in STEMI patients and the prognostic value was comparable to or even higher traditional scores. Trial registration ChiCTR1900028516 (http//www.chictr.org.cn).