High plasma heparin cofactor II activity protects from restenosis after femoropopliteal stenting.

High heparin cofactor II (HCII) activity has recently been described to protect from coronary instent restenosis, presumably by inactivating thrombin in injured arteries. In this study, we investigated the association of HCII activity and restenosis after femoropopliteal stenting. We studied 63 consecutive patients with peripheral artery disease who underwent femoropopliteal stent implantation after initial failure of plain balloon angioplasty due to a significant residual stenosis (>30% lumen diameter reduction) or a flow limiting dissection. HCII activity was measured before stenting and patients were followed for median 10 months (interquartile range 6 to 17) for the occurrence of a first instent restenosis, defined as a >50% lumen diameter reduction by color coded duplex sonography and confirmed by angiography. Cumulative freedom from restenosis at 6 and 12 months in patients with lower HCII activity (100%, lower tertile, n=20) was 84% and 35% as compared to 93% and 72% in patients with high HCII activity (>100%, middle and upper tertile, n=43; p=0.024 by Log Rank test). Adjusting for the material of the implanted stents (nitinol vs. Wallstents), patients with a high HCII activity had a 0.39-fold reduced risk for instent restenosis (95% CI 0.17 to 0.90, p=0.028), additional adjustment for diabetes mellitus, poor run-off, critical limb ischemia and cumulative length of the stented segment did not alter the observed effect. Higher activity of heparin cofactor II may exert a protective effect against instent restenosis also in the femoropopliteal vessel area, confirming a prior observation after coronary stenting.

Pharmacodynamics of active site-inhibited factor VIIa in endotoxin-induced coagulation in humans.

BACKGROUND: Inhibition of the tissue factor-factor VIIa pathway attenuated the activation of coagulation and prevented death in a gram-negative bacteremia primate model of sepsis. This lethal animal model suggested that tissue factor also influences inflammatory cascades. METHODS: This trial examined the pharmacodynamic effects of active site-inhibited factor VIIa (FFR-recombinant factor VIIa [rFVIIa]; ASIS) on endotoxin-induced procoagulant, fibrinolytic, and inflammatory responses in healthy humans. A double-blind, randomized, placebo-controlled, parallel-group study was conducted in 12 healthy male volunteers. Subjects received a bolus infusion of 2-ng/kg endotoxin, followed by a bolus infusion of ASIS (400 microg/kg) or placebo 10 minutes later. RESULTS: Endotoxin injection induced inflammation, activation of coagulation, and activation and subsequent inhibition of fibrinolysis. ASIS infusion completely blocked thrombin and fibrin generation, as measured by plasma levels of prothrombin fragment (no increase in the ASIS group, as compared with a 13-fold increase in the placebo group at 4 hours; P <.01), soluble fibrin, and fibrin split product D-dimer. ASIS did not alter endotoxin-induced changes in the fibrinolytic system, cytokine levels, or markers of endothelial (E-selectin, thrombomodulin) or platelet (P-selectin) activation. CONCLUSIONS: In summary, ASIS effectively and selectively attenuates tissue factor-induced thrombin generation. Because ASIS was well tolerated, this study provides seminal data to further characterize its anticoagulant and putative anti-inflammatory effects in critically ill patients.

Effect of factor X inhibition on coagulation activation and cytokine induction in human systemic inflammation.

Anticoagulants have gained increasing attention in the treatment of sepsis. This study used danaparoid to investigate the role of factor Xa in endotoxin-induced coagulation and inflammation and its effectiveness when coagulation activation has already occurred. Thirty healthy volunteers were enrolled in the randomized, placebo-controlled trial. Subjects received 2 ng/kg endotoxin and danaparoid 10 min or 3 h thereafter or placebo. Endotoxin increased prothrombin fragment 1+2 (F(1+2)) levels from 0.5 to 7.0 nmol/L at 5 h in the placebo group. Early danaparoid infusion inhibited endotoxin-induced thrombin formation: maximum F(1+2) levels reached only 1.8 nmol/L (P<.01, vs. baseline or placebo). Delayed danaparoid infusion effectively blocked further thrombin formation. However, danaparoid did not alter endotoxin-induced changes in the fibrinolytic system, cytokine levels, activation of leukocytes, or tissue factor expression on monocytes. Danaparoid therefore selectively attenuates endotoxin-induced coagulopathy, even with delayed administration when coagulation activation is well under way.

Acenocoumarol decreases tissue factor-dependent coagulation during systemic inflammation in humans.

BACKGROUND: Coumarin derivatives are still widely used for prophylaxis of thromboembolic events and therefore represent important comparator substances for new anticoagulants. Measurement of the efficacy of such novel compounds in a human coagulation model with adequate biomarkers could be useful for early-phase clinical drug development. To evaluate the applicability of a well-established model of tissue factor-dependent coagulation for defining anticoagulant potency, we investigated the effects of acenocoumarol in experimental human endotoxemia. METHODS: In a randomized, controlled, 2-by-2 factorial design, healthy volunteers received an infusion of 2 ng/kg endotoxin or placebo after 18 days of pretreatment with acenocoumarol or placebo. Prothrombin fragment 1+2 (F(1+2)), soluble fibrin, and D-dimer were used as markers of thrombin and fibrin formation. RESULTS: As expected, pretreatment with acenocoumarol decreased vitamin K-dependent coagulation factors, but it also decreased spontaneous thrombin formation. Acenocoumarol inhibited endotoxin-induced thrombin generation as measured by F(1+2) levels: endotoxin infusion increased F(1+2) levels 8-fold-from 0.5 to 4.1 nmol/L-in the placebo group, whereas peak F(1+2) levels reached only 1.0 nmol/L in subjects after acenocoumarol pretreatment. This inhibition was also reflected in decreased formation of soluble fibrin and decreased D-dimer levels, showing that depletion of endogenous coagulation factors limits the propagation of nonovert disseminated intravascular coagulation. CONCLUSIONS: Human endotoxemia is a suitable tool for measurement of the efficacy of oral anticoagulants and therefore may become a valuable addition for expeditious pharmacodynamic characterization of lead compounds with anticoagulant potency.