The initial anion gap is a predictor of mortality in acute myocardial infarction

OBJECTIVE: To determine the relationship between the anion gap and outcomes in patients with acute myocardial infarction. METHODS: We assessed the relationship between the initial anion gap and in-hospital outcomes among consecutive acute myocardial infarction patients admitted to a single coronary care unit. The anion gap was calculated as [sodium-(chloride+CO2)]. Anion gap>12 was considered to represent anion gap acidosis. RESULTS: Complete data were available for 773 patients. Anion gap acidosis on admission was found in 90 patients (12%), and was more common among older patients (P=0.02), women (P=0.008), non-whites (P=0.04), and patients with diabetes (P=0.03), chronic renal failure (P<0.001), a lower glomerular filtration rate (P<0.001), and cardiogenic shock (P<0.001). In-hospital death occurred in 33% of patients with initial anion gap acidosis compared with 8% in those with a normal anion gap (P<0.001). On multivariate analysis, the presence of an initial anion gap acidosis was associated with the risk of death (odds ratio 4.2, 95% confidence interval 2.3-7.5, P<0.001), independent of other data available at the time of admission. The addition of ejection fraction to the model significantly attenuated this association. CONCLUSIONS: The admission anion gap provides important incremental information for initial risk stratification in acute myocardial infarction.