Proteolysis of Tissue Factor Pathway Inhibitor-1 by Thrombolysis in Acute Myocardial Infarction

BACKGROUND: In acute myocardial infarction (AMI), surface-bound tissue factor pathway inhibitor-1 (TFPI-1) inhibits an increased monocyte procoagulant activity. In addition, TFPI-1 is released from microvascular endothelial cells after treatment with heparin and thereby contributes to its antithrombotic properties. METHODS AND RESULTS: We examined 19 patients in a randomized study comparing intravenous fibrinolysis with alteplase (n=9) and revascularization by stent placement with additional abciximab treatment (n=10). We obtained blood samples for analysis of monocytic TFPI-1 surface expression by flow cytometry and plasma TFPI-1 concentrations by immunoassay before and after therapy. We found a significant decrease in surface TFPI-1 on circulating monocytes 24 hours after thrombolysis (P=0.006) that was not observed after stenting. Systemic plasma TFPI-1 concentrations increased immediately after stenting by 71+/-14% (P=0.008), whereas after thrombolysis, a decrease in TFPI-1 plasma concentrations of 21+/-11% was observed (P=0.075). In vitro experiments confirmed that plasmin decreased TFPI-1 surface expression dose-dependently. CONCLUSIONS: Activation of the fibrinolytic system by alteplase in AMI decreases surface-associated TFPI-1 on circulating monocytes and plasma TFPI-1. Reduced TFPI-1 may contribute to thrombotic complications after fibrinolysis in AMI.