Renal function and anaemia in acute myocardial infarction

Impaired renal function and anaemia are common among patients with acute myocardial infarction (AMI). While both conditions are known independent risk factors for increased mortality, their interaction as risk factors for increased mortality in AMI is unclear.

We studied 5395 subjects hospitalized for AMI between January 2000 and December 2005. An estimated glomerular filtration rate (GFR) <60 mL/min/1.73 m(2) was defined as impaired GFR and GFR ≥ 60 mL/min/1.73 m(2) was defined as preserved GFR. Anaemia was defined as <13 g/dL (males) and <12 g/dL (females). The odds ratio (OR) for one-year mortality and its 95% confidence interval (CI) were calculated by logistic regression.

We identified 758 (14%) patients with impaired GFR and anaemia, 1105 (20.5%) patients with impaired GFR without anaemia, 465 (8.6%) patients with preserved GFR and anaemia, and 3012 (55.8%) patients with preserved GFR without anaemia; one-year mortality rates were 56.5%, 41.8%, 31.8% and 10.3% respectively in these 4 groups. Among patients with impaired GFR, anaemia was associated with an adjusted OR of 1.47 (95% CI=1.17-1.85) for one-year mortality, while among patients with preserved GFR, anaemia was associated with a higher adjusted OR of 2.07 (95% CI=1.54-2.76) for one-year mortality, interaction P<0.001.

The combination of impaired GFR and anaemia confers greater than five-fold increased risk of mortality after AMI. The differential effect of anaemia among patients with impaired and preserved GFR on mortality suggests that in patients with preserved GFR anaemia confers a greater relative hazard than in patients with impaired renal function.