Serum blood urea nitrogen and long-term mortality in acute ST-elevation myocardial infarction

Introduction Renal dysfunction is associated with increased mortality in acute coronary syndromes and other cardiovascular diseases. The prognostic value of kidney dysfunction has been investigated using creatinine-based measures of renal function. Few data are available on the prognostic significance of blood urea nitrogen (BUN), a sensitive marker of hemodynamic alterations and renal perfusion. Methods The relationship between estimated glomerular filtration rate (eGFR), BUN on admission and changes in BUN during hospital course and long-term mortality was evaluated in 1507 patients with acute ST-elevation myocardial infarction (STEMI). Results During a median follow-up of 27 months (range, 12 to 44 months), 281 patients (18.6%) died. In multivariable Cox regression models, elevated BUN (≥ 25 mg/dL) at admission was an independent predictor of mortality after adjustments for clinical variables and eGFR (adjusted hazard ratio [HR] 1.7; 95% confidence interval [CI] 1.2–2.3, P = 0.0015). Similar results were obtained for elevated BUN/creatinine ratio (≥ 25) at admission (adjusted HR 2.0; 95% CI 1.4–2.8; P < 0.0001). An increase in BUN 50% above admission value occurred in 260 of patients (17.3%) during hospital course, and was associated with increased risk of mortality after adjustments of clinical variables, eGFR and BUN on admission (HR, 1.7 95% CI 1.3–2.2; P < 0.0001). Discussion Elevated BUN and BUN/creatinine ratio on admission are independent predictors of long-term mortality in patients with STEMI. An increase in BUN level during hospital course portends adverse outcome independent of eGFR and BUN on admission.