Loss of Heparin-Releasable Tissue Factor Pathway Inhibitor in Patients Undergoing PTCA

Arterial thrombosis for the interventional cardiologist: From adhesion molecules and coagulation factors to clinical therapeutics

Arterial thrombosis is the result of a complex and well-orchestrated set of events where interactions between platelets and leukocytes are intertwined with enzymatic reactions of the coagulation system. Here, we present a contemporary panorama of arterial thrombosis and provide a framework the interventionalist can use to understand the current antithrombotic pharmacotherapies and recognize the role of therapies that have yet to be developed. We analyze thrombosis in the context of plaque rupture and vascular injury and describe the interactions between platelets and the subendothelium. We then discuss platelet-leukocyte interactions, emphasizing the inflammatory nature of thrombosis and how this relates to vessel restenosis following angioplasty. The different reactions of the coagulation system are described not from an isolated perspective, but are integrated into the sequence of cell-cell interactions that parallel them. Finally, we describe the mechanisms that terminate the thrombotic response.

Hypercoagulability, high tissue factor and low tissue factor pathway inhibitor levels in severe ovarian hyperstimulation syndrome: possible association with clinical outcome

During ovarian gonadotrophin stimulation for ovulation induction or in vitro fertilization, a clinical severe ovarian hyperstimulation syndrome (OHSS) may occur. Only few studies have investigated the mechanism responsible for the alterations of the haemostatic system in women affected by severe OHSS. The aim of the present study was to investigate the correlation between the magnitude of ovarian stimulation and the increase in fibrin formation and degradation in severe OHSS. Twenty-five patients (age range 23-43 years) who were hospitalized for severe OHSS, 25 women undergoing in vitro fertilization who did not develop OHSS (case-control group) and 25 healthy age-matched women (healthy control group) were investigated. On the day of admission a number of haemostatic markers, including D-dimer, thrombin-antithrombin complexes (TAT), prothrombin fragment 1 + 2 (F1 + 2), plasmin-antiplasmin complexes (PAP), tissue factor (TF), tissue factor pathway inhibitor (TFPI) and von Willebrand factor antigen (vWF), were examined. In patients with severe OHSS, TF, D-dimer, TAT, F1 + 2, PAP and vWF antigen plasma levels were significantly higher than those observed both in the case-control group and in healthy controls, whereas TFPI levels were significantly lower (P < 0.005) with respect to both case-controls and healthy controls. D-Dimer levels were related with serum oestradiol levels and oocyte number recovered (r = 0.45, P < 0.001 and r = 0.47, P < 0.001, respectively). D-Dimer and TAT levels were significantly (P < 0.05 and P < 0.005, respectively) higher in OHSS patients with unsuccessful pregnancy outcome (D-dimer, 226.5, 56-1449 ng/ml; TAT, 19.8, 3.1-82.6 microg/l) with respect to those with successful outcome of pregnancy (D-dimer, 145, 29-330 ng/ml; TAT, 5.0, 1.0-19.6 microg/l). Our data indicate that a marked hypercoagulability with alterations of TF and TFPI levels is detectable in patients with severe OHSS and that it is related to the clinical outcome.

Analysis of the tissue factor pathway inhibitor gene and antigen levels in relation to venous thrombosis

Tissue factor pathway inhibitor (TFPI) inhibits tissue factor-induced coagulation. The major part of TFPI is releasable by heparin. We recently found eight patients with thrombosis and low levels of heparin-releasable TFPI in whom we investigated the TFPI gene for mutations. A transition of G to A coding for Valine264Methionine in the heparin-binding domain was found. The Val264Met polymorphism had an allele frequency of 3% in 96 healthy individuals. A silent polymorphism was identified in TFPI exon IV (T-->C), which does not alter Tyrosine 56. Apart from Val264Met, which was detected in one out of the eight patients, no other mutations in the TFPI gene were found in patients with low heparin-releasable TFPI. Analysis of Val264Met in 317 patients with deep vein thrombosis (DVT) and 292 controls showed no association between Val264Met and DVT. However, a study of total TFPI antigen levels in 122 DVT patients and 126 controls demonstrated an association between TFPI levels and venous thrombosis (P = 0.0001). These results provide evidence for a relationship between venous thrombosis and total TFPI level as a possible risk factor, whereas they do not support a link between DVT and mutations in the nine exons of the TFPI gene.

Differential effect of unfractionated heparin and low molecular weight heparin on intravascular tissue factor pathway inhibitor: evidence for a difference in antithrombotic action

Tissue factor pathway inhibitor (TFPI) is a potent inhibitor of tissue factor (TF)-induced blood coagulation, which is increased several-fold in post-heparin plasma and thought to contribute significantly to the antithrombotic action of heparin. In the present study we investigated whether subcutaneous (s.c.) administration of a low molecular weight heparin (LMWH), enoxaparin, had a different effect on intravascular pools of TFPI compared with continuous i.v. infusion of unfractionated heparin (UFH). 18 healthy male volunteers were randomly assigned to continuous i.v. infusion with UFH (initially 450 U/kg/24 h, n = 6) or to s.c. treatment with LMWH once daily (enoxaparin, 1.5 mg/kg, n = 12) for 72 h. A bolus injection of 5000 IU UFH i.v. caused an 8-13-fold increase in plasma-free TFPI antigen (TFPI Ag), followed by a progressive decrease (81 +/- 4%, P<0.001) during the 72 h infusion with UFH. 4 h after discontinuation of the infusion, basal free TFPI Ag and heparin-releasable TFPI were significantly decreased compared with the concentrations before the infusion (30 +/- 9%, and 27 +/- 7%, respectively). In contrast, LMWH treatment did not reduce either basal or heparin-releasable TFPI Ag. The changes in plasma TFPI Ag by UFH and LMWH were statistically different between groups both in pre- (P<0.001) and post-heparin (P<0.0001) plasma. The differential effect of UFH and LMWH on intravascular pools of TFPI may contribute to the understanding of the apparent superior efficacy of LMWHs in the treatment of both arterial and venous thrombosis.