BACKGROUND

Although elevated serum urea and low serum sodium have been shown to be associated with increased short-term (30-day) mortality following an ST-elevation myocardial infarction (STEMI), little is known about the role of these biochemical markers as predictors of intermediate-term (1-year) re-hospitalisation.

METHODS

Case notes of 90 consecutively admitted patients discharged with a primary diagnosis of an STEMI were retrospectively investigated. Baseline parameters were recorded and patients' clinical course following hospital discharge was carefully reviewed up to 1-year post-STEMI. Multivariate logistic regression analysis was performed to determine the independent association between baseline parameters and 1-year re-hospitalisation.

RESULTS

The mean age of the patients was 62.8+/-1.38 years. Thirty patients (33.3%) were re-hospitalised for cardiac-related events and three patients (3.3%) died within 1 year of index STEMI. Using stepwise regression analysis, after adjusting for all independent variables, admission total cholesterol (p=0.013) and urea (p=0.04) were found to be the only significant independent predictors of re-hospitalisation or death. Admission serum sodium was non-significant (p=0.065), but only just. For each mmol/L increase in total cholesterol, a patient was 2.18 times more likely to be re-hospitalised, while for each mmol/L increase in serum urea, a patient was 1.32 times more likely to be re-hospitalised or die. When data were categorised based on high urea >> 7 mmol/L), high total cholesterol >> 5.0 mmol/L) and low sodium (< 135 mmol/L) at admission, none of these variables showed any significant increased risk of re-hospitalisation or death. This suggests that these biochemical parameters were continuously associated with risk of re-hospitalisation through the whole range of serum concentrations.

CONCLUSIONS

In this retrospective study, independent predictors of 1-year re-hospitalisation following an STEMI include high serum urea, raised cholesterol levels and, possibly, reduced sodium levels. These simple biomarkers can be included in patients' risk stratification when following post-STEMI patients in out-patient clinics.