The association between white blood cell count and acute myocardial infarction mortality in patients > or =65 years of age: findings from the cooperative cardiovascular project.

Objectives: The purpose of the study was to examine the association between white blood cell (WBC) count on admission and 30-day mortality in patients with acute myocardial infarction (AMI).

Background: Elevations in WBC count have been associated with the development of AMI and with long-term mortality in patients with coronary artery disease. However, the relationship between WBC count and prognosis following AMI is less clear.

Methods: Using the Cooperative Cardiovascular Project database, we evaluated 153,213 patients > or = 65 years of age admitted with AMI.

Results: An increasing WBC count is associated with a significantly higher risk of in-hospital events, in-hospital mortality and 30-day mortality. Relative to those patients in the lowest quintile, patients in the highest quintile were three times more likely to die at 30 days (10.3% vs. 32.3%; p < 0.001). After adjustment for confounding factors, WBC count was found to be a strong independent predictor of 30-day mortality (odds ratio = 2.37; 95% confidence interval 2.25 to 2.49, p = 0.0001 for the highest quintile of WBC count).

Conclusions: White blood cell count within 24 h of admission for an AMI is a strong and independent predictor of in-hospital and 30-day mortality as well as in-hospital clinical events. Although the mechanism of the association remains speculative, the results of this study have important clinical implications for risk-stratifying patients with AMI.