Effect of anemia on 1-year mortality in patients with acute myocardial infarction.

BACKGROUND Limited data are available on the effect of anemia on mortality in patients with acute myocardial infarction (MI). METHODS We examined the association of anemia with mortality at 1 year among 30,341 patients hospitalized with acute MI in 1986 (prethrombolytic era, n = 15,584) and 1996 (thrombolytic era, n = 14,757). The records were obtained from the Myocardial Infarction Data Acquisition System, a database of all patients with MI admitted to nonfederal hospitals in New Jersey. RESULTS Anemia was present in 996 patients (6.4%) in 1986 and 1510 patients (10.2%, P <.0001) in 1996. In both years, patients with anemia were older, more frequently female and nonwhite, and more likely to have left ventricular dysfunction, non-Q MI and coronary artery bypass graft. In addition, in 1996, patients with anemia were more likely to undergo percutaneous transluminal coronary angioplasty and less likely to have a history of MI. One-year mortality was lower overall in 1996 compared with 1986 (1996 23.6%, 95% CI 22.9-24.3 vs 1986 24.9%, 95% CI 24.2-25.6, P =.0001). In both years, patients with anemia had significantly higher unadjusted risk for 1-year mortality (RR = 1.40, P =.0001 in both years). However, after controlling for demographics, left ventricular dysfunction, arrhythmias, Q versus non-Q MI, comorbid conditions, and revascularization procedures in a multivariable regression model, 1-year mortality in the anemia group was similar to the nonanemia group in both years. CONCLUSION In the Myocardial Infarction Data Acquisition System database, anemia appears to have no significant direct effect on 1-year mortality. The higher unadjusted mortality observed among patients with acute MI and anemia is probably the result of older age, higher comorbidity, and more left ventricular dysfunction.