Circulating activated factor XI and active tissue factor as predictors of worse prognosis in patients following ischemic cerebrovascular events.

Background: Elevated factor (F)XI is associated with an increased risk for ischemic stroke. Activated FXI (FXIa) and tissue factor (TF) have not been studied following stroke. The aim of the current study was to evaluate circulating FXIa and TF in patients with prior cerebrovascular events.

Patients/methods: We studied 241 patients, including 162 after ischemic stroke and 79 after transient ischemic attack (TIA), recruited 6 months to 4 years (median, 36 months) after the events. Plasma TF and FXIa activity following the index event were determined in clotting assays by measuring the response to inhibitory monoclonal antibodies.

Results: Active TF was detected in 25 (10.4%) of the patients, while FXIa activity (median, 37.5 [IQR 397] pM) was found in 64 (26.7%) of the patients (p<0.01). The prevalence of active TF and FXIa was higher in subjects with previous stroke compared with those with a history of TIA (13% vs 5.1%, p=0.05, and 34% vs 11.4%, p<0.0001, respectively). Patients with circulating FXIa were younger and had higher fibrinogen and interleukin-6 compared to the remainder. Patients with detectable TF or FXIa activity had higher NIHSS score, higher modified Rankin scale and lower Barthel Index than the remaining subjects (all p<0.05).

Conclusion: Circulating active TF and FXIa can occur in patients with cerebrovascular ischemic events ≥6 months after the events. The presence of these factors is associated with worse functional outcomes, which highlights the role of persistent hypercoagulable state in cerebrovascular disease.