Circulating markers that indicate atherosclerotic plaque instability may have diagnostic and prognostic value in patients with acute coronary syndromes. We evaluated activated protein C (APC), which has antithrombotic, anti-inflammatory, and profibrinolytic properties, as a possible clinical predictor in ST-elevation myocardial infarction (STEMI), including return of spontaneous circulation after sudden cardiac arrest.

Patients with STEMI whose APC level was measured upon arrival at the emergency room were enrolled in this study (n = 335). The primary end point was inhospital death from any cause.

The APC level ranged from 29% to 142% with a median of 80%. The unadjusted death rate increased in a stepwise fashion with decreasing APC levels (33.7% in quartile 1, 12.7% in 2, 6.0% in 3, and 3.6% in 4, P < .001). This association remained significant in subgroups of patients with STEMI only (P = .04) or with return of spontaneous circulation (P = .01). After adjusting for independent predictors of inhospital death, the odds ratio for death among those in the first quartile of APC levels was 9.4 (95% CI 1.1-81.6, P = .04). A cutoff APC level of 65% had the highest combined sensitivity and specificity in predicting death.

Measuring APC levels provides predictive information for use in risk stratification across the STEMI spectrum. Decreased APC levels may be a unifying feature among patients at high risk for death after STEMI.