Activated factor XII (FXIIa) is involved in vascular injury and repair, participating in inflammation, thrombosis, and fibrinolysis. We wanted to test the hypothesis that FXIIa may predict an acute coronary syndrome (ACS) after a myocardial infarction (MI) and to evaluate whether FXIIa is related to global markers of end-stage coagulation and inflammation, including fibrin monomer (FM) and ultrasensitive C-reactive protein (μCRP).

In a prospective study of 300 patients with acute MI, we evaluated the predictive value of FXIIa in blood samples drawn 4 to 6 days after admission. Cardiac death, re-MI, and troponin-T–positive unstable angina pectoris were registered during a median follow-up period of 1.5 years.

In the upper quartile of FXIIa (Q4) (≥2.23 ng/mL) 32.0% of patients had an ACS as compared with 16.9% of patients with FXIIa in the three lower quartiles (Q1-3, P = .008). Relative risk of recurrent ACS for patients with FXIIa in the Q4 as compared with Q1-3 was 1.89 (95% CI, 1.22 to 2.93). A secondary ACS occurred earlier in patients with FXIIa in the Q4 as compared with those with FXIIa in the Q1-3 (P = .0039). Conventional risk factors as potential confounders were not associated with time to event. FXIIa did not correlate with FM or μCRP, and the FM and μCRP levels were of a similar magnitude in the Q4 as compared with the Q1 and the Q1-3 of FXIIa.

FXIIa predicts recurrent coronary events after MI. The prognostic ability of FXIIa was not reflected by markers of hypercoagulability or inflammation.