Markers of inflammation, including high-sensitivity C-reactive protein, are powerful indicators of the development of myocardial infarction and other acute coronary events, and valuable predictors of adverse prognosis in patients with unstable angina. The white blood cell (WBC) count is a simpler and more readily available marker of inflammation. Patients with acute myocardial infarction who have elevated WBC counts appear to be at higher risk of mortality and recurrent acute myocardial infarction (AMI).
Cannon and associates used data obtained from the Orbofiban in Patients with Unstable Coronary Syndromes trial to look at the impact of WBC count. The study included more than 10,000 patients who had experienced AMI or unstable angina pectoris and had an associated high-risk feature. The participants were treated daily with aspirin and randomized to receive one of two dosing regimens of orbofiban, an oral glycoprotein IIb/IIIa inhibitor, or placebo. The primary study end point was a composite of death, AMI, recurrent ischemia at rest leading to hospitalization, urgent revascularization or stroke. Patients were stratified by WBC count at baseline (an average of 41 hours after the onset of the acute coronary syndrome). Outcomes at 30 days and 10 months were compared between the groups.
Mortality at 30 days showed a significant increase in patients with an increasing WBC count. The combination of death or myocardial infarction, thrombotic stroke, and the development of new or worsening congestive heart failure or cardiogenic shock was also more frequent among the 18 percent of patients with WBC counts of 10,000 per mm3 (10 × 109 per L) or higher. Outcomes at 10 months showed persistent excess mortality among patients with an elevated WBC count. The relative risk of mortality among patients with a markedly increased WBC count (greater than 15,000 per mm3 [15 × 109 per L]) was significantly higher than that in patients with WBC counts between 10,000 and 15,000 per mm3.
The authors conclude that a WBC count above 10,000 per mm3, even on the second hospital day, is a potent predictor of adverse outcomes of mortality or nonfatal events in patients with acute myocardial infarction and unstable angina.