A High Level of Blood Urea Nitrogen Is a Significant Predictor for In-hospital Mortality in Patients with Acute Myocardial Infarction

High levels of blood urea nitrogen (BUN) have been demonstrated to significantly predict poor prognosis in patients with acute decompensated heart failure. However, this relationship has not been fully investigated in patients with acute myocardial infarction (AMI). We investigated whether a high level of BUN is a significant predictor for in-hospital mortality and other clinical outcomes in patients with AMI. The Japanese registry of acute Myocardial INfarction diagnosed by Universal dEfiniTion (J-MINUET) is a prospective, observational, multicenter study conducted in 28 institutions, in which 3,283 consecutive AMI patients were enrolled. We excluded 98 patients in whom BUN levels were not recorded at admission and 190 patients who were undergoing hemodialysis. A total of 2,995 patients were retrospectively analyzed. BUN tertiles were 1.5-14.4 mg/dL (tertile 1), 14.5-19.4 mg/dL (tertile 2), and 19.5-240 mg/dL (tertile 3). Increasing tertiles of BUN were associated with stepwise increased risk of in-hospital mortality (2.5, 5.1, and 11%, respectively; P < 0.001). These relationships were also observed after adjusting for reduced estimated glomerular filtration rate (estimated GFR < 60 mL/minute/1.73 m(2)) or Killip classifications. In multivariable analysis, high levels of BUN significantly predicted in-hospital mortality, after adjusting for creatinine and other known predictors (BUN tertile 3 versus 1, adjusted odds ratio [OR]: 2.59, 95% confidence interval [95% CI]: 1.57-4.25, P < 0.001; BUN tertile 2 versus 1, adjusted OR: 1.60, 95% CI: 0.94-2.73, P = 0.081). A high level of BUN could be a useful predictor of in-hospital mortality in AMI patients.