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

To determine the relationship between the anion gap and outcomes in patients with acute myocardial infarction.

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.

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.

The admission anion gap provides important incremental information for initial risk stratification in acute myocardial infarction.