Patients with acute coronary syndromes have low tissue factor activity and microparticle count, but normal concentration of tissue factor antigen in platelet free plasma - a pilot study

Tissue factor (TF) is a main initiator of coagulation cascade. Its determination in conditions of acute coronary syndrome is logistically difficult. Hence, in our study, the activity and the concentration of TF and the count of microparticles in the platelet free plasma (PFP) were determined. Blood was drawn from both coronary sinus and femoral vein circulation in a cohort of 40 patients. TF activity was measured by activation of factor X in the presence of factor VIIa, whereas microparticles were detected using flow cytometry. TF antigen concentrations were determined using the ELISA test. TF activity in the stable angina subgroup was not significantly different from the control group (18.12 +/- 3.35 mOD/min vs. 17.72 +/- 4.05 mOD/min, respectively), but it was significantly lower in the unstable angina (7.62 +/- 4.19 mOD/min) and myocardial infarction (MI) (3.56 +/- 3.85 mOD/min) subgroups (P < 0.05). Results from the coronary sinus and femoral vein circulations were not significantly different. The count of microparticles decreased according to the severity of the acute coronary syndrome: control group, 520 +/- 172; stable angina subgroup, 532 +/- 167; unstable angina subgroup, 392 +/- 142; and MI subgroup, 165 +/- 30 (P < 0.05). There were no significant differences in concentrations of TF antigen in four subgroups. These results suggest that the procoagulant TF-bearing microparticles could be recruited from PFP by interaction with platelets and blood cells in the conditions of acute coronary syndrome.